Zhi-Gan Formula improved insomnia and anxiety comorbidity in a mouse model via PACAP signaling in the medial prefrontal cortex.

ETHNOPHARMACOLOGICAL RELEVANCE: Insomnia and anxiety are highly comorbid, severely compromising quality of life. Efficacy of current pharmacological interventions for this dual condition remains limited. Zhi-Gan Formula (ZG), consisting of Zhi-Zi-Chi Decoction and Ganmai Dazao Decoction, two classic Traditional Chinese Medicine (TCM) formulae clinically widely used for insomnia or anxiety, holds promise as a therapeutic option for insomnia-anxiety comorbidity. AIM OF THE STUDY: This study aimed to assess ZG’s sleep-promoting and anxiolytic efficacy, and investigate the novel mechanism through which pituitary adenylate cyclase-activating polypeptide (PACAP) in the medial prefrontal cortex (mPFC) modulates comorbid sleep and anxiety conditions. MATERIALS AND METHODS: Mice received 4-chloro-DL-phenylalanine (PCPA) injections and were subsequently administered ZG or diazepam. Behaviors were assessed using the pentobarbital-induced sleep test, open-field test (OFT), and elevated plus-maze test (EPM). Key pathways were identified via network pharmacology analysis and validated using long-term potentiation (LTP) recordings and protein quantification. Viral-mediated PACAP knockdown vectors were transfected into the mPFC. RESULTS: PCPA administration induced insomnia and anxiety-like behaviors. ZG administered for 3 days significantly shortened sleep latency, prolonged sleep duration, and alleviated anxiety-like behaviors, whereas diazepam only partially improved anxiety-like behaviors. Network pharmacology analysis suggested ZG’s engagement in neuropeptide-receptor interactions and synaptic transmission pathways. Assessments of synaptic plasticity showed that ZG improved mPFC LTP and the expression of synaptic proteins (PSD95, synapsin-1, BDNF) impaired in the model mice. Moreover, the expression of the neuropeptide PACAP and downstream eEF2 signaling for synaptic protein synthesis were all improved by ZG. Crucially, perfusion of a PACAP agonist in the mPFC brain slices from sleep-deprived mice rescued LTP deficits. Finally, mPFC PACAP knockdown abolished the therapeutic effects and the enhanced expressions of the synaptic proteins by ZG. CONCLUSIONS: ZG alleviated insomnia-anxiety comorbidity by restoring synaptic plasticity in the mPFC via the PACAP-eEF2-BDNF pathway, which may also shed light on the development of a novel therapeutic approach for the treatment of sleep-anxiety comorbidity.