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

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.

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.

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.

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.

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.