Central Neurobiological Mechanisms of Acupuncture in Post-Stroke Depression: Multi-Target and Network-Based Regulation

Introduction

Post-stroke depression (PSD) is one of the most prevalent neuropsychiatric complications following stroke, with an incidence ranging from 30% to 50%,^1,2 and it severely impairs neurological recovery and quality of life. Accumulating evidence indicates that PSD not only increases stroke-related disability and mortality,³ but is also strongly associated with reduced activities of daily living, cognitive impairment, and deterioration of sleep quality.^4–6 Moreover, depressive symptoms have been shown to correlate positively with the risk of stroke recurrence.⁷ At present, conventional pharmacological treatments for PSD exhibit substantial limitations. Meta-analyses have demonstrated that only approximately 50% of patients respond adequately to antidepressant therapy,¹ and treatment is frequently accompanied by adverse effects such as gastrointestinal disturbances and sexual dysfunction.⁸ In elderly patients, age-related declines in metabolic capacity further increase the risk of serious side effects, including falls and QT interval prolongation.⁹ The global burden of PSD varies considerably across regions, with higher incidence reported in low- and middle-income countries, possibly due to disparities in stroke care and mental health resources. Emerging biomarkers, including inflammatory cytokines (eg, IL-6, TNF-α), neurotrophic factors (BDNF), and gut microbiota-derived metabolites, are being investigated to improve PSD diagnosis and risk stratification. Historically, acupuncture has been used to treat depressive-like symptoms in traditional Chinese medicine for centuries, with classical texts such as the Huangdi Neijing describing needling techniques for “melancholy” disorders. These historical roots complement the modern neurobiological mechanisms discussed in this review, bridging traditional holistic concepts with contemporary multi-target elucidation. Consequently, there is an urgent clinical need for safe and effective alternative therapeutic strategies.

As a non-pharmacological intervention, acupuncture has demonstrated distinctive advantages in the management of PSD. Randomized controlled trials have shown that acupuncture combined with conventional treatment significantly reduces Hamilton Depression Rating Scale (HAMD) scores, while the incidence of adverse events is only approximately 16% of that observed in pharmacotherapy groups.¹⁰ The therapeutic effects of acupuncture are characterized by a multi-target mode of action: it can modulate monoaminergic neurotransmitters such as serotonin (5-hydroxytryptamine, 5-HT) and norepinephrine (NE),¹¹ while simultaneously suppressing the release of proinflammatory cytokines, including interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α).¹² This bidirectional regulatory capacity may underlie the superior efficacy of acupuncture compared with single-target pharmacological agents. In recent years, advances in neurobiological techniques have provided new perspectives for elucidating the central mechanisms of acupuncture in the treatment of PSD. Functional magnetic resonance imaging studies have demonstrated that acupuncture enhances functional connectivity between the prefrontal cortex and the limbic system,¹³ thereby ameliorating depression-related negative emotional processing biases. At the molecular level, evidence suggests that acupuncture can reduce post-ischemic neuronal apoptosis by activating AMP-activated protein kinase (AMPK)-dependent autophagy,¹⁴ and upregulate brain-derived neurotrophic factor (BDNF) expression to promote synaptic plasticity.¹⁵ Furthermore, animal studies have revealed that acupuncture suppresses activation of the colonic NOD-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome via modulation of the gut microbiota–brain axis,¹⁶ providing experimental support for its “multi-pathway” mode of action. Despite these advances, a comprehensive and systematic review focusing on the central neurobiological mechanisms by which acupuncture ameliorates PSD is still lacking.

Elucidating the central mechanisms of acupuncture in PSD holds considerable theoretical and practical significance. From a theoretical perspective, it facilitates a deeper understanding of the holistic regulatory features of acupuncture and helps to clarify the intrinsic links between the holistic concepts of traditional Chinese acupuncture and modern neurobiology. From clinical and research perspectives, mechanistic insights can fill existing gaps in the literature and inform the optimization of therapeutic strategies, such as guiding individualized acupoint selection¹⁷ or identifying optimal therapeutic windows through dynamic monitoring of inflammatory biomarkers.¹⁸ Therefore, a systematic synthesis of recent advances in the central mechanisms underlying acupuncture-mediated improvement of PSD will not only provide a solid theoretical basis for clinical practice but also open new avenues for future research.

Clinical Application of Acupuncture in the Treatment of Post-Stroke Depression

Clinical studies have demonstrated that acupuncture is effective in alleviating symptoms of post-stroke depression (PSD) and is associated with a relatively low incidence of adverse events, suggesting its potential as a complementary or alternative therapeutic approach. Representative clinical studies investigating acupuncture for PSD are summarized in Table 1.

Table 1 Representative Clinical Protocols and Outcomes of Acupuncture Treatment for Post-Stroke Depression

Pathophysiological Mechanisms of Post-Stroke Depression

The pathogenesis of PSD arises from multilevel pathophysiological cascades triggered by the stroke event, the initiating processes of which involve acute neuronal necrosis and excitotoxic injury within the ischemic core, as illustrated in Figure 1. These injuries not only directly disrupt synaptic architecture and mitochondrial function but also induce the release of damage-associated molecular patterns (DAMPs), which activate microglia and elicit pronounced neuroinflammatory responses in both local and remote brain regions.¹⁸ A single-cell sequencing study by Li et al demonstrated increased populations of microglia and endothelial cells in the hippocampus of PSD models, with functional enrichment analyses indicating blood–brain barrier reinforcement and activation of inflammatory pathways.²⁴ Against the backdrop of acute injury and persistent inflammation, the processes of neuroplastic reconstruction are markedly suppressed.²⁵

Figure 1 Mechanisms underlying the development of post-stroke depression (PSD).The pathogenesis of PSD involves a multifaceted cascade initiated by acute ischemic injury, which triggers local neuroinflammation (indicated by ↑ for increased IL‑1β and TNF‑α) and disrupts neuroplasticity. This is further compounded by monoaminergic neurotransmitter dysfunction (indicated by ↓ for decreased 5‑HT, NE, and DA), hyperactivation of the hypothalamic‑pituitary‑adrenal (HPA) axis, and dysregulation of the gut‑brain axis (indicated by ↑ for increased intestinal permeability and ↓ for decreased short‑chain fatty acids, SCFAs). Together, these processes lead to mitochondrial dysfunction, neuronal loss in mood‑regulating brain regions, and the manifestation of depressive symptoms. The dark red arrows illustrate the causal progression that drives the entire pathological cascade toward PSD.

A chronic inflammatory microenvironment, downregulation of brain-derived neurotrophic factor (BDNF), and sustained oxidative stress synergistically impede hippocampal neurogenesis and synaptic plasticity remodeling. Qian et al reported that inhibition of the BDNF signaling pathway, mediated by miR-409-3p, attenuates tropomyosin receptor kinase B (TrkB) activation, thereby compromising the adaptive capacity of neural circuits involved in emotional regulation.²⁶ In addition, oxidative stress–related factors, such as acetylation modifications of nuclear factor erythroid 2–related factor 2 (Nrf2), play a critical role in PSD²⁷ and influence BDNF transcriptional activity and neuronal survival.²⁸

Stroke-related injury and inflammatory responses can extend to monoaminergic nuclei, including the raphe nuclei and locus coeruleus,²⁹ and, through systemic inflammation–mediated remodeling of tryptophan metabolism, lead to functional impairment of neurotransmitter systems such as serotonin (5-HT), norepinephrine (NE), and dopamine (DA).^30,31 This imbalance in neurotransmitter networks further weakens reward circuitry activity and disrupts emotional homeostasis. Pharmacological interventions by Lu et al demonstrated that modulation of monoamine oxidase A (MAOA) activity improves neurotransmitter levels and alleviates depression-like behaviors.³²

Throughout this process, the neuro–immune–endocrine regulatory axis remains persistently activated. Interactions between peripheral and central inflammatory mediators, together with hyperactivity of the hypothalamic–pituitary–adrenal (HPA) axis and the resulting elevated cortisol levels, exert synergistically detrimental effects on emotion-related brain regions such as the hippocampus.³³ Sun et al reported that increased levels of systemic low-grade inflammatory markers, including C-reactive protein (CRP) and fibrinogen, are associated with a higher risk of PSD, and mediation analyses revealed that inflammation partially mediates the relationship between stroke severity and depressive symptoms.¹⁸

Disruption of bidirectional regulation along the brain–gut axis also contributes to the pathophysiology of PSD.³⁴ Post-stroke dysbiosis of the gut microbiota and increased intestinal barrier permeability facilitate endotoxin translocation and alter microbial metabolites, such as short-chain fatty acids, thereby exacerbating systemic and central inflammatory responses via neural and humoral pathways.³⁵ Experimental evidence from Chen et al showed that modulation of the gut microbiota, through approaches such as fecal microbiota transplantation or pharmacological regulation, ameliorates depression-like behaviors and downregulates the P2X7 receptor (P2X7R)/NLRP3 inflammasome signaling pathway.³⁶ Moreover, Sirtuin 6 (Sirt6)–mediated regulation of the gut microbiota plays an important role in PSD by influencing oxidative damage and inflammatory cytokine levels.³⁷

Ultimately, these pathological alterations converge at the cellular level as mitochondrial energy metabolism dysfunction and activation of multiple programmed cell death pathways, including apoptosis and pyroptosis, leading to progressive neuronal loss in key emotion-regulating brain regions such as the prefrontal cortex, hippocampus, and limbic system.²⁴ Zhou et al further demonstrated that activation of the NLRP3 inflammasome promotes neuronal pyroptosis and reduced neuronal excitability, thereby contributing to imbalances in neural network function.³⁸ This mechanistic framework, characterized by progression from focal injury to systemic functional dysregulation, provides a pathophysiological basis for multi-target therapeutic strategies, such as acupuncture or pharmacological interventions, and underscores the necessity of integrated treatments targeting inflammation, neuroplasticity, and the gut microbiota.³²

Mechanistic Studies on Acupuncture in the Improvement of PSD

Acupuncture Improves Cerebral Neural Function

Promotion of Neuroplasticity

Enhancement of neuroplasticity can ameliorate PSD through multiple mechanisms, including strengthening brain functional connectivity, reducing neuroinflammation, and promoting neurogenesis.³⁹ Acupuncture has been shown to facilitate neuroplasticity, primarily by activating the BDNF/TrkB signaling pathway and improving synaptic structure and function.

First, acupuncture exerts a crucial role in improving PSD by regulating the expression of brain-derived neurotrophic factor (BDNF) and its receptor tropomyosin receptor kinase B (TrkB). Kang et al demonstrated that EA stimulation at Hegu (LI4) and LR3 significantly increased the number of BDNF- and TrkB-positive cells in the hippocampus of PSD rats, with antidepressant effects comparable to fluoxetine but with a more rapid onset.⁴⁰ The tissue-type plasminogen activator (tPA)/BDNF/TrkB signaling pathway represents a key mechanism underlying the anti-PSD effects of acupuncture. Dong et al reported that EA stimulation at GV20, Yinjiao (GV29), Zhongwan (CV12), and Guanyuan (CV4) increased tPA expression, thereby elevating levels of mature BDNF (mBDNF) and activating TrkB receptors, an effect that was attenuated by a tPA-specific inhibitor.⁴¹ Zhu et al further showed that tPA intervention reversed the reduced expression of microglial BDNF and TrkB in the amygdala of PSD rats,⁴² suggesting that acupuncture may exert its effects by modulating BDNF/TrkB signaling at the neuroimmune interface. In addition, Povarnina et al found that the BDNF mimetic GSB-106 could replicate the effects of acupuncture by activating downstream TrkB signaling pathways, including MAPK/ERK, PI3K/AKT, and PLCγ, thereby improving depression-like behaviors and memory impairment following cerebral ischemia.⁴³ Collectively, these findings indicate that acupuncture activates the BDNF/TrkB pathway through multi-target mechanisms, with different acupoint combinations exerting neuroprotective effects via this pathway.⁴⁴ However, such regulation exhibits brain region specificity. Sun et al reported that acupuncture not only upregulated BDNF and TrkB mRNA and protein expression in the hippocampal CA1 region but also increased the p-CREB/CREB ratio, thereby activating the CREB/BDNF/TrkB signaling pathway and alleviating depression-like behaviors in PSD rats.⁴⁵ Nevertheless, although the regulatory effects of EA on the BDNF/TrkB pathway have been established, the upstream regulatory mechanisms and the dose–effect relationships with different acupuncture parameters (eg, frequency, intensity, and waveform) remain unclear. Moreover, most studies have focused on a limited number of acupoints, and systematic comparisons and mechanistic differentiation among different acupoint protocols are still lacking.

Second, acupuncture has demonstrated significant effects in improving synaptic structure and function in PSD.⁴⁶ Pan et al confirmed that EA stimulation at GV24 and bilateral GB13 repaired synaptic structure and function in a mouse model of post-ischemic stroke depression.⁴⁷ This study further indicated that EA enhanced the expression of NGL-3 in the medial prefrontal cortex (mPFC), promoted its interaction with the presynaptic protein L1cam, and facilitated the formation of vesicular glutamate transporter 1 (vGluT1)-positive synaptic vesicles, thereby strengthening excitatory synaptic transmission.⁴⁷ However, studies employing specific knockout of NGL-3 in cortical neurons are still lacking to conclusively validate this mechanism. Regulation of synapse-associated protein expression represents another important mechanism by which acupuncture improves synaptic transmission efficiency. In this context, Han et al found that EA stimulation at Fengchi (GB20) enhanced synaptic function and upregulated the expression of key molecules involved in maintaining synaptic structural and functional integrity, including postsynaptic density protein 95 (PSD95) and synaptophysin (Syn),⁴⁸ findings that are consistent with those reported by Li D.⁴⁹ Together, these studies suggest that EA optimizes synaptic structure and function through multi-target and multi-pathway actions, providing a neurobiological basis for the treatment of PSD.As summarized in Figure 2, acupuncture exerts its therapeutic effects on PSD primarily by modulating neuroplasticity, including the regulation of synaptic plasticity, promotion of neurogenesis, and restoration of neural network balance.As shown in Figure 2, acupuncture alleviates PSD primarily by promoting neuroplasticity.

Figure 2 Acupuncture Promotes Neuroplasticity to Improve PSD.Mechanisms by which acupuncture promotes neuroplasticity in post-stroke depression. Electroacupuncture activates the tPA/BDNF/TrkB signaling pathway (tPA expression↑; proBDNF → mBDNF, indicating conversion to mature BDNF; mBDNF↑; p-TrkB↑), leading to downstream activation of MAPK/ERK, PI3K/AKT, and PLCγ cascades, as well as CREB-mediated transcription. In parallel, acupuncture enhances synaptic structure and function by upregulating synapse-associated proteins (NGL-3 expression↑, vGluT1↑, PSD95↑, synaptophysin↑), thereby promoting neurogenesis↑, neuronal survival↑, synaptic plasticity↑, synaptic integrity↑, and excitatory synaptic transmission↑. Collectively, these changes restore hippocampal and prefrontal cortical neural plasticity and improve depressive-like behaviors.

Regulation of Neural Network Remodeling and Brain Functional Connectivity

Regulation of neural network remodeling and brain functional connectivity represents another important mechanism by which EA improves PSD, primarily through modulation of brain network connectivity and neuronal activity, as illustrated in Figure 3. Acupuncture has been shown to modulate functional connectivity within the default mode network (DMN), which is closely associated with depression. In a controlled study of PSD patients, Wei et al found that after treatment, electroencephalography (EEG) revealed significant increases in α- and β-band power spectra, and the imaginary coherence–based functional connectivity across multiple frequency bands was markedly higher than that in the sham acupuncture group, indicating that acupuncture ameliorates depressive symptoms by enhancing fast-wave activity and cerebral functional connectivity.¹³

Figure 3 Acupuncture Regulates Neural Network Remodeling and Brain Functional Connectivity to Improve PSD.EA alleviates depressive symptoms by enhancing functional connectivity within brain networks (eg, the default mode network) and increasing neuronal activity in key regions such as the primary motor cortex (M1) and medial prefrontal cortex (mPFC), as reflected by increased excitatory neuronal activity↑, functional connectivity↑, imaginary coherence↑, beta power↑, and alpha power↑. These effects involve the activation of specific neural circuits and signaling pathways, including PI3K/Akt/mTOR and JNK, ultimately leading to neural network reorganization and subsequent improvement of depressive‑like behaviors,as indicated by the arrow “Neural network reorganization → Improvement of depressive-like behaviors” in the figure.

Acupuncture can also improve neural function and alleviate depressive symptoms by regulating neuronal activity. Studies have shown that acupuncture significantly enhances neuronal activity in the primary motor cortex (M1) on the non-infarcted side. Yao et al reported that EA stimulation at Lianquan (CV23) activated excitatory neurons in layer V (L5) of the contralateral M1, thereby promoting compensatory motor function and modulating emotion-related behaviors via the cortical–pontine–nucleus tractus solitarius (M1–PBN–NTS) neural circuit.⁵⁰ Similarly, Sun et al found that EA at Dazhui (GV14), Shuigou (GV26), GV20, and GV24 in a PSD mouse model enhanced neuronal activation in the medial prefrontal cortex (mPFC) and primary somatosensory cortex (PSC), while promoting the formation and transmission of excitatory synapses.⁴⁷ The underlying mechanisms involve multiple signaling pathways, including the PI3K/Akt/mTOR pathway⁵¹ and the c-Jun N-terminal kinase (JNK) pathway.⁴⁷

At the functional network level, the regulatory effects of acupuncture on neuronal activity are also reflected in improvements in cortical network connectivity. Deng et al demonstrated that EA stimulation at GV20 and GV24 restored electrophysiological activity of mPFC neurons in PSD mice, with effects comparable to those of fluoxetine.⁵² Collectively, these studies reveal that acupuncture regulates neuronal activity through multi-target and multi-pathway mechanisms to improve PSD. However, the causal chain underlying these mechanisms remains incomplete. Most studies have demonstrated correlations between acupuncture and improvements in neuronal activity and network connectivity, but direct causal verification is lacking. For example, it remains unclear whether the antidepressant effects of acupuncture would be abolished when neuronal excitability in specific regions such as the primary motor cortex (M1) or the medial prefrontal cortex (mPFC) is selectively inhibited, which limits definitive identification of the core brain regions and circuits involved.

Promotion of Hippocampal Neurogenesis

Acupuncture can exert antidepressant effects by promoting hippocampal neurogenesis, as illustrated in Figure 4. In a PSD mouse model, Li et al demonstrated that electroacupuncture (EA) at ST36 significantly increased the number of granule cells and doublecortin (DCX)-positive cells in the dentate gyrus while reducing neuronal apoptosis, indicating that EA protects hippocampal structure by enhancing neurogenesis and inhibiting cell death.⁵³ In other depression models, EA stimulation at GV23 and Fengfu (GV16) has similarly been shown to significantly alleviate depression-like behaviors, with underlying mechanisms associated with enhanced hippocampal neurogenesis and regulation of the Wnt/β-catenin signaling pathway.⁵⁴ In addition, Liu et al reported that in a model of chronic neuropathic pain comorbid with depression, EA at GV20 restored adult neurogenesis in the ventral dentate gyrus, not only increasing the number of newly generated neurons but also normalizing their dendritic morphology.⁵⁵ Pei W further found that EA at Sishencong (EX-HN1) promoted hippocampal neurogenesis and synaptic plasticity by activating the BDNF/TrkB/ERK signaling pathway.⁵⁶

Figure 4 Acupuncture Promotes Hippocampal Neurogenesis to Improve PSD.EA exerts antidepressant effects by enhancing neurogenesis in the hippocampal dentate gyrus, increasing the survival and maturation of newborn neurons, and modulating key signaling pathways such as BDNF/TrkB/Erk and Wnt/β-catenin. In the figure, upward arrows (↑) indicate an increase (eg, DCX+ cells↑, granule cells↑, newborn neurons↑, Wnt/β-catenin↑, BDNF/TrkB/ERK↑), while the downward arrow (↓) indicates a decrease (apoptosis↓).

Taken together, acupuncture promotes neurogenesis in the hippocampal dentate gyrus, enhances both the quantity and quality of newly generated neurons, and ultimately improves hippocampus-dependent cognitive function, constituting an important central neurobiological mechanism underlying its therapeutic effects on PSD and other affective disorders. Although current studies have confirmed the promotive effects of EA on hippocampal neurogenesis, there remains a substantial lack of direct mechanistic investigations specifically focused on post-stroke depression models.

In summary, acupuncture enhances cerebral neural function in PSD by promoting neuroplasticity via the BDNF/TrkB pathway, remodeling neural networks and functional connectivity, and stimulating hippocampal neurogenesis. These actions collectively restore the structural and functional integrity of emotion-regulating brain regions, forming a central neural basis for its antidepressant effects.

Regulation of Neurotransmitter Systems

Acupuncture can enhance the activity of serotonergic neurons in the dorsal raphe nucleus, thereby improving PSD. Clinical studies provide direct evidence for this effect. Yin ZL reported that acupuncture using the Shugan Tiaoshen protocol at EX-HN1, GV20, EX-HN3, and GV24 significantly increased serum 5-hydroxytryptamine (5-HT) levels in PSD patients, resulting in marked antidepressant effects.¹⁵ Kalaoğlu et al also observed that after four weeks of acupuncture treatment, PSD patients showed a reduced need for dose escalation of selective serotonin reuptake inhibitors (SSRIs).⁵⁷ In animal studies, Deng et al similarly found that EA reversed the reduction in the number of 5-HT–positive neurons in the dorsal raphe nucleus of PSD model mice.⁵²

Following the increase in 5-HT induced by acupuncture, the underlying mechanism involves activation of subcutaneous mast cells at acupoints. Activated mast cells release mediators, including 5-HT, into the interstitial space. Subsequently, 5-HT acts on corresponding receptors (eg, 5-HT receptors) located on local sensory nerve endings, reducing the electrical activity of primary sensory neurons, thereby inhibiting nociceptive signal transmission and alleviating depressive symptoms.⁵⁸ In addition, 5-HT may act in concert with other neurotransmitter systems, such as dopamine (DA) and norepinephrine (NE), by modulating the neuro–endocrine–immune network, jointly promoting synaptic repair and neural network remodeling, and ultimately exerting synergistic antidepressant effects.⁵⁹

The improvement of PSD by acupuncture also involves broad regulation of monoaminergic neurotransmitter systems, including DA and NE. Clinical studies have confirmed that acupuncture combined with escitalopram oxalate in the treatment of mild to moderate PSD significantly increases serum DA and NE levels, with superior therapeutic effects compared with pharmacotherapy alone.¹¹ Ma et al further reported that acupuncture, particularly EA, can regulate glutamate (Glu) levels in the brains of animal models of depression.⁶⁰ In the context of PSD, post-stroke brain injury often leads to an imbalance between excitation and inhibition; acupuncture may help restore neural circuit homeostasis in affected brain regions by bidirectionally regulating the Glu/γ-aminobutyric acid (GABA) system, thereby alleviating depressive symptoms.

Moreover, the antidepressant effects of acupuncture are not mediated by a single neurotransmitter system but rather depend on the coordinated actions of multiple neurotransmitter systems. The neuro–endocrine–immune (NEI) network theory provides an integrative framework, in which neurotransmitters, hormones, and cytokines are interconnected.⁶¹ Acupuncture can amplify the effects of the NEI network, achieving integrative regulation across multiple systems. Xie et al demonstrated that acupuncture not only increases monoaminergic neurotransmitters such as 5-HT, DA, and NE but also modulates the “microbiota–gut–brain axis,” influencing gut microbiota composition and indirectly regulating central neurotransmitter metabolism and function.⁶² In addition, acupuncture can activate signaling pathways such as BDNF/ERK/mTOR, which are closely associated with neuroplasticity and can coordinately regulate the function of multiple neurotransmitter systems, ultimately promoting synaptic repair and neural network remodeling.⁶³ Therefore, acupuncture treatment for PSD represents a multi-target and multi-pathway intervention strategy that exerts synergistic antidepressant effects through coordinated regulation of multiple neurotransmitter systems and related signaling networks.⁶⁴

In summary, acupuncture exerts holistic antidepressant effects by coordinately regulating multiple classes of neurotransmitters, balancing excitatory and inhibitory systems, and integrating multiple signaling pathways,as illustrated in Figure 5. However, the precise molecular mechanisms, the clinical translation of findings from animal studies, heterogeneity among research protocols, and evidence for long-term efficacy remain to be fully elucidated. Future studies employing advanced technologies and rigorous experimental designs are needed to further clarify these regulatory mechanisms.

Figure 5 Acupuncture Regulates Neurotransmitter Systems to Improve PSD.EA restores monoaminergic neurotransmission (DA↑, with reward and motivation↑; NE↑, with arousal and stress regulation↑; 5-HTergic neuron activity↑;5-HT levels↑), balances excitatory/inhibitory signaling, and coordinates multi-system interactions via the neuro-endocrine-immune network to exert synergistic antidepressant effects.→ indicates a causal or sequential relationship.

In summary, acupuncture exerts holistic antidepressant effects by coordinately regulating multiple neurotransmitter systems, including increasing serotonin, dopamine, and norepinephrine levels, and rebalancing the glutamate/GABA system. This multi‑transmitter modulation, acting through the neuro‑endocrine‑immune network, underlies the integrated therapeutic action of acupuncture in PSD.

Inhibition of Neuroinflammation

Acupuncture can improve PSD by modulating microglial activity, as illustrated in Figure 6. Li et al and Chen et al both reported that acupuncture at GV20, EX-HN33, and related acupoints significantly reduced microglial activation in the prefrontal cortex and hippocampus.^65,66 Li et al further demonstrated that electroacupuncture (EA) at ST36 in PSD mice markedly decreased the expression of ionized calcium-binding adapter molecule 1 (Iba-1) in the hippocampus and inhibited its colocalization with NOD-like receptor family pyrin domain-containing 3 (NLRP3).⁵³ These findings indicate that suppression of aberrant microglial activation constitutes a key neuroimmune basis for the antidepressant effects of acupuncture in PSD. Following inhibition of microglial activation, acupuncture exerts its effects at multiple levels.⁶⁷

Figure 6 Acupuncture Inhibits Neuroinflammation to Improve PSD.EA ameliorates depressive symptoms by inhibiting microglial overactivation (Iba-1↓, M1 phenotype↓), promoting their shift toward an anti‑inflammatory M2 phenotype (Arg-1↑, M2↑, BDNF↑), and downregulating key pro‑inflammatory signaling pathways (eg, TLR4/NF-κB/NLRP3) and inflammatory cytokines (IL-1β↓, IL-6↓, TNF-α↓), as well as reducing pyroptosis (Caspase-1↓, Pyroptosis↓), thereby improving the neural immune microenvironment.→ indicates a causal or sequential relationship.

First, suppression of microglial activation by acupuncture reduces the release of proinflammatory cytokines, including interleukin-1β (IL-1β), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α). For example, in PSD mouse models, EA treatment significantly lowered elevated levels of IL-1β, IL-6, and TNF-α in the hippocampus.⁵³ Second, acupuncture can modulate microglial phenotypes, promoting polarization toward the anti-inflammatory and neuroprotective M2 phenotype. Zou et al found that in a cerebral ischemia mouse model, EA treatment facilitated microglial polarization toward the M2 phenotype, as evidenced by increased expression of the anti-inflammatory mediator arginase-1 (Arg-1) and brain-derived neurotrophic factor (BDNF), a process that was partially mediated by annexin A1 (ANXA1).⁶⁸ The resulting improvement in the inflammatory microenvironment contributes to attenuation of neuronal injury and apoptosis.⁶⁹

The anti-inflammatory effects of acupuncture in PSD also involve regulation of the toll-like receptor 4 (TLR4)/p38/nuclear factor-κB (NF-κB)/NLRP3 signaling pathway. Cai et al demonstrated that EA stimulation at DU20 and DU24 inhibited the TLR4/NF-κB/NLRP3 signaling pathway, thereby effectively alleviating depression-like behaviors in PSD model mice. These effects were closely associated with suppression of NLRP3 inflammasome activation and a reduction in pyroptosis.⁷⁰

In summary, acupuncture effectively attenuates neuroinflammation by inhibiting aberrant microglial activation, promoting polarization toward the M2 phenotype, and downregulating key inflammatory signaling pathways such as TLR4/NF-κB/NLRP3, thereby improving the neuroimmune microenvironment in PSD. However, the specific upstream signaling molecules through which acupuncture regulates microglial activity remain unclear; whether different acupoints and stimulation parameters exert distinct effects requires systematic comparison; and the long-term impact of acupuncture on microglia–neuron interactions has yet to be elucidated.

In summary, acupuncture attenuates neuroinflammation in PSD by inhibiting aberrant microglial activation, promoting M2 phenotypic polarization, and suppressing the TLR4/NF-κB/NLRP3 signaling pathway. These anti‑inflammatory effects improve the neuroimmune microenvironment and reduce neuronal injury, contributing significantly to its antidepressant efficacy.

Improvement of Mitochondrial Function and Inhibition of Cell Death

Improvement of mitochondrial function and inhibition of cell death represent another important mechanism underlying the therapeutic effects of acupuncture,as illustrated in Figure 7. Yin et al reported that the “Shugan Tiaoshen” acupuncture protocol, involving stimulation at GV20, EX-HN33, LI4, and LR3, activated AMP-activated protein kinase (AMPK)–dependent autophagy in PSD rats, upregulated the expression of Beclin-1 and the LC3-II/I ratio, and promoted the clearance of damaged mitochondria, thereby restoring mitochondrial structural and functional homeostasis.¹⁴ Chen et al further demonstrated that, with respect to energy metabolism, acupuncture enhanced AMPK activity and promoted the expression of key proteins involved in mitochondrial biogenesis, such as peroxisome proliferator–activated receptor γ coactivator-1α (PGC-1α), leading to improved neuronal ATP production capacity.⁷¹ These findings provide molecular-level evidence supporting the role of acupuncture in alleviating PSD by improving mitochondrial function and offer new perspectives for clinical intervention.

Figure 7 Acupuncture Improves Mitochondrial Function and Inhibits Cell Death to Improve PSD.EA enhances mitochondrial quality via AMPK-dependent autophagy and biogenesis (AMPK↑, Beclin1↑, LC3‑II/I↑, PGC‑1α↑, ATP production↑), and concurrently suppresses multiple cell death pathways, including ferroptosis (Fe2+↓, lipid peroxidation↓, MDA↓, GSH↑, GPX4↑, ACSL4↓, LOX↓), apoptosis (Bax↓, Bcl‑2↑, cleaved caspase‑3↓; accompanied by increased H3K9ac/H3K27ac at the Bcl‑2 promoter↑ and decreased histone acetylation at the caspase‑3 gene↓), and pyroptosis (NLRP3↓, caspase‑1↓, IL‑1β↓), thereby preserving neuronal survival and function.

Acupuncture also regulates multiple cell death pathways. Meng et al found that EA alleviated neural injury in the prefrontal cortex and hippocampus by inhibiting ferroptosis and neuronal apoptosis.^72,73 Ferroptosis, an iron-dependent form of cell death driven by lipid peroxidation, plays a critical role in the pathophysiology of PSD.⁷⁴ Wu et al reported that EA stimulation at GV20, EX-HN33, and related acupoints reduced iron ion content and malondialdehyde (MDA) levels in the prefrontal cortex, while upregulating glutathione (GSH) and the antioxidant enzyme glutathione peroxidase 4 (GPX4), and inhibiting the activity of pro-ferroptotic factors such as lipoxygenase (LOX) and acyl-CoA synthetase long-chain family member 4 (ACSL4).⁷³

In addition, acupuncture exerts neuroprotective effects through regulation of the c-Jun N-terminal kinase (JNK)/c-Jun signaling pathway. Meng et al showed that EA at GV20 downregulated the expression of pro-apoptotic proteins Bax and cleaved caspase-3, while upregulating the anti-apoptotic protein Bcl-2. Moreover, EA increased histone acetylation at H3K9 and H3K27 in the promoter region of the Bcl-2 gene, thereby enhancing its transcription, while reducing histone acetylation of the caspase-3 gene to suppress its expression.⁷⁵ Li et al further demonstrated that EA at GV20 and EX-HN33 attenuated activation of the NLRP3 inflammasome in the prefrontal cortex, reduced caspase-1–mediated pyroptosis and interleukin-1β (IL-1β) release, and consequently alleviated neuroinflammation and neuronal injury.⁷⁶ Collectively, these findings provide experimental evidence that acupuncture improves PSD through multi-target regulation of diverse cell death pathways.

In summary, acupuncture restores mitochondrial homeostasis via AMPK‑dependent autophagy and simultaneously inhibits multiple cell death pathways, including apoptosis, pyroptosis, and ferroptosis. This multi‑faceted protection of neuronal energy metabolism and survival provides a critical subcellular mechanism for its therapeutic effects in PSD.

Exploration of the Gut–Brain Axis Mechanism

In recent years, increasing attention has been paid to the role of acupuncture in improving PSD through modulation of the gut microbiota.⁶² Studies have shown that acupuncture can effectively regulate the composition of the gut microbiota in PSD model animals, thereby exerting antidepressant effects.⁷⁷ For example, Cai et al reported that in PSD model rats, acupuncture at GV20, GV24, and bilateral ST36 significantly increased gut microbial diversity, enhanced the abundance of beneficial bacteria, and reduced the relative abundance of harmful bacteria.¹⁶ These alterations further influenced the production and distribution of microbial metabolites, thereby mediating beneficial effects on the central nervous system. Research on acupuncture-mediated improvement of PSD via regulation of the gut microbiota provides new insights and experimental evidence for in-depth exploration of the gut–brain axis mechanism, suggesting that the antidepressant effects of acupuncture are associated with multidimensional regulation of the “neuro–immune–microbiome” network.⁷⁸

First, modulation of the gut microbiota can suppress excessive activation of the NLRP3 inflammasome in the colon and reduce serum levels of proinflammatory cytokines such as interleukin-1β (IL-1β) and interleukin-18 (IL-18), thereby alleviating systemic and neuroinflammation.¹⁶ Second, acupuncture can inhibit inflammatory signaling pathways distributed along the gut–brain axis, including the toll-like receptor 4 (TLR4)/myeloid differentiation factor 88 (MyD88)/nuclear factor-κB (NF-κB) pathway, reduce microglial activation in the hypothalamus and colon, and stabilize hypothalamic–pituitary–adrenal (HPA) axis function.⁷⁸ Third, acupuncture enhances intestinal barrier integrity by upregulating the expression of tight junction proteins, such as occludin, zonula occludens-1 (ZO-1), and claudin-4, thereby preventing translocation of endotoxins and other harmful substances into the circulation.⁷⁹ These effects have also been confirmed in PSD rat models.³⁷

Collectively, these findings indicate that acupuncture regulates gut–brain axis function through multi-target mechanisms, providing a novel theoretical basis for the treatment of PSD, as illustrated in Figure 8. Future studies should further deepen the understanding of the physiological pathways through which acupuncture modulates the gut microbiota and their integrated mechanisms,⁸⁰ in order to promote more precise application of acupuncture in the treatment of neuropsychiatric disorders.

Figure 8 Gut–Brain Axis Mechanisms of Acupuncture in Improving PSD.EA improves depressive symptoms by restoring gut microbiota balance (beneficial bacteria↑, harmful bacteria↓, gut microbiota diversity↑), enhancing intestinal barrier integrity (intestinal barrier integrity↑, tight junction proteins↑, occludin↑, ZO-1↑, claudin-4↑, endotoxin translocation↓), and subsequently inhibiting neuroinflammation and HPA axis hyperactivity (colonic NLRP3 inflammasome↓, TLR4/MyD88/NF-κB↓, peripheral inflammation↓, IL-1β↓, IL-18↓, microglial activation↓, neuroinflammation↓, HPA axis stabilization, stress hormone dysregulation↓), thereby coordinating the neuro-immune-microbiome network.

In summary, acupuncture modulates the gut–brain axis by reshaping gut microbiota composition, enhancing intestinal barrier integrity, suppressing colonic NLRP3 inflammasome activation, and inhibiting TLR4/MyD88/NF-κB signaling. These effects reduce systemic and central inflammation, stabilize HPA axis function, and represent a novel peripheral mechanism complementing the central actions described above.We have summarized in Table 2 the key mechanistic pathways of acupuncture for PSD discussed in this section, including the representative studies, experimental models, and main findings for each mechanism.

Table 2 Comparison of Key Mechanistic Pathways Implicated in Acupuncture for PSD

Research Challenges and Future Directions

Research on acupuncture for PSD exhibits notable deficiencies in clinical translation, which are mainly reflected at three levels. First, mechanistic studies rely excessively on animal experiments, limiting clinical extrapolation. Although animal studies have identified potential targets across multiple levels, including synaptic plasticity,⁴⁷ neurotransmitter regulation,⁵² and cell death pathways,⁷⁰ animal models cannot adequately capture the psychosocial dimensions of human disease. Moreover, the highly standardized experimental conditions differ substantially from the heterogeneity encountered in clinical practice, thereby constraining direct translation of these findings. Second, there is a lack of clinical studies that directly validate biological mechanisms. Although meta-analyses and real-world studies have confirmed the advantages and safety of acupuncture in improving clinical outcomes such as Hamilton Depression Rating Scale (HAMD) scores,^81–83 most investigations focus primarily on symptom assessment. High-quality clinical studies that directly verify the in vivo alterations of key pathways identified in animal experiments remain scarce. A limited number of studies combining functional magnetic resonance imaging (fMRI) or event-related potential (ERP) techniques to explore brain networks or cognitive function represent promising translational directions;^84,85 however, both their scale and depth are insufficient. Third, treatment protocols and outcome evaluation systems lack standardization. Considerable variability exists in acupoint selection (eg, Baihui,⁵² Siguan points⁴⁰), stimulation parameters, and treatment duration, while efficacy evaluation relies predominantly on rating scales, with limited incorporation of objective biological biomarkers. Future translational research urgently requires the establishment of standardized treatment protocols and the development of multidimensional evaluation systems integrating clinical assessments, neuroimaging, and biofluid molecular biomarkers, supported by rigorously designed large-scale clinical trials to bridge the gap between basic and clinical research.

Current investigations into the central mechanisms of acupuncture for PSD also face methodological limitations. First, there is insufficient integration of research approaches. Clinical studies largely depend on behavioral rating scales and single-modality neuroimaging, such as fMRI, with limited systematic and dynamic analyses of brain functional networks. Moreover, few studies integrate cerebrospinal fluid or peripheral blood biomarkers to elucidate mechanisms from a neuro–immune perspective.^86,87 Second, there is a lack of neurophysiological monitoring techniques with high temporal and spatial resolution. Human studies predominantly rely on indirect blood oxygenation signals, while animal studies, although capable of employing calcium imaging to observe activity in specific neuronal populations⁸⁸ or fiber photometry to detect acupuncture-induced modulation of dopaminergic neuronal firing,⁸⁹ still lack tools that enable whole-brain, cell-type–specific, real-time monitoring in freely behaving state.⁹⁰ Future research should integrate advanced technologies, such as high-field fMRI, simultaneous fMRI–EEG, and flexible neural probes, to more comprehensively elucidate the mechanisms underlying acupuncture.

Furthermore, several limitations exist in current acupuncture research for PSD. First, most clinical trials have small sample sizes and short follow‑up periods (typically ≤12 weeks), lacking assessments of long‑term efficacy and safety.^86,91 Second, blinding is inherently difficult to achieve in acupuncture studies; a systematic review revealed that blinding status in sham acupuncture groups is often compromised, with a high proportion of participants correctly guessing their group assignment, potentially introducing performance and detection biases.⁹² Third, substantial heterogeneity exists across studies in acupoint selection, electroacupuncture parameters (frequency, intensity, waveform), treatment frequency, and duration, which limits the integration of results and the reliability of meta‑analyses.^93,94 Fourth, publication bias may exist, whereby studies with positive results are more likely to be published, potentially overestimating the true effect size of acupuncture.

Compared with non‑acupuncture interventions such as antidepressants, acupuncture for PSD has both potential advantages and limitations. A systematic review on major depressive disorder by Zhao et al explicitly stated that the conclusion of comparable efficacy between acupuncture and antidepressants originated from “very low‑quality evidence”.⁹⁵ Similarly, the study by Zhou et al noted that research in the PSD field is constrained by design flaws and short follow‑up periods,⁹⁶ and Zhang et al pointed out that any claimed efficacy advantage of acupuncture over standard pharmacotherapy (eg, reduction in HAMD scores) lacks reliable validation.⁹⁷ Furthermore, head‑to‑head comparisons of acupuncture with other non‑pharmacological interventions (eg, cognitive‑behavioral therapy, repetitive transcranial magnetic stimulation) are extremely scarce, and the existing literature provides neither sufficient evidence that acupuncture is superior to these interventions nor evidence of non‑inferiority. Consequently, given the generally low certainty of evidence, a robust judgment on the definitive advantages or disadvantages of acupuncture relative to various non‑acupuncture interventions cannot be made. Future high‑quality, directly comparative randomized controlled trials with rigorous designs, adequate sample sizes, and long‑term follow‑up are urgently needed to clarify the relative positioning of acupuncture in the comprehensive treatment pathway for PSD.

To further advance the field and address the limitations outlined above, we propose the following prioritized research agendas:First, causal validation using optogenetics and chemogenetics. Current mechanistic studies largely rely on correlational observations (eg, changes in BDNF expression or microglial activity following acupuncture). Optogenetic or chemogenetic manipulation of specific neuronal populations (eg, dopaminergic neurons in the ventral tegmental area or serotonergic neurons in the dorsal raphe nucleus) in PSD animal models could establish causal links between acupuncture-induced neural activity changes and behavioral improvements. For example, selectively inhibiting or activating these pathways during acupuncture would determine whether they are necessary or sufficient for antidepressant effects.Second, multi‑omics integration for systems-level understanding. Acupuncture’s multi-target nature calls for systems biology approaches. Integrating transcriptomics, proteomics, metabolomics, and microbiomics from the same animal models or clinical cohorts could reveal how acupuncture coordinately regulates neuroplasticity, neuroinflammation, and gut‑brain axis pathways. Such multi‑omics analyses may identify novel hub molecules or pathways that are not apparent from single‑mechanism studies, facilitating the discovery of predictive biomarkers for patient stratification.Third, advanced neuroimaging for dynamic circuit mapping. While fMRI has shown acupuncture’s effects on brain networks, future studies should employ simultaneous fMRI‑EEG, high‑field (≥7T) MRI, or mesoscale calcium imaging in awake animals to track real‑time changes in circuit-level activity across the whole brain during and after acupuncture. This would help decode the spatiotemporal dynamics of acupuncture’s network-based actions.Fourth, large-scale, biomarker‑integrated clinical trials. Beyond confirming efficacy, future randomized controlled trials should incorporate predefined mechanistic biomarkers (eg, serum BDNF, IL-6, gut microbial profiles) as secondary endpoints or stratification factors. This would not only validate the translational relevance of the mechanisms discussed in this review but also move toward personalized acupuncture therapy based on individual biomarker signatures.

Conclusion

Research into the central mechanisms of acupuncture in the treatment of post-stroke depression (PSD) has progressively revealed a multilevel integrative mode of action spanning molecular, cellular, and neural network levels. From the perspective of modern neurobiology, these findings substantiate that acupuncture exerts therapeutic effects through multiple pathways, including regulation of neuroplasticity, neurotransmitter balance, inflammatory responses, mitochondrial function, and the gut–brain axis. More importantly, they highlight the scientific value of the traditional Chinese medicine principles of holism and syndrome differentiation in contemporary disease intervention.

The deepening of mechanistic research provides biological interpretations for therapeutic principles such as “soothing the liver and regulating the mind” and “unblocking the Governor Vessel to awaken the brain,” thereby promoting the optimization of acupuncture protocols from empirical practice toward mechanism-guided strategies. At the same time, the elucidation of “multi-target synergistic” action networks lays a foundation for the development of integrative therapeutic approaches that incorporate the holistic regulatory advantages of acupuncture. Looking forward, continued in-depth investigation of acupuncture mechanisms, combined with the application of modern neuroscience to interpret traditional acupuncture theory, will not only be crucial for enhancing the clinical efficacy of PSD treatment but will also open broader avenues for the integrative management of neuropsychiatric disorders through the convergence of traditional Chinese and Western medicine.Specifically, future studies should prioritize large-scale, multicenter randomized controlled trials that integrate mechanistic biomarkers (eg, serum BDNF, inflammatory cytokines) to validate the multi-target effects of acupuncture and guide patient stratification for personalized treatment.