Effects of endomorphin-1 (EM-1) and endomorphin-2 (EM-2) on synaptic transmission were investigated on neurons in substantia gelatinosa (SG) of the spinal dorsal horn by whole-cell voltage clamp recording. Both EM-1 (1 μmol/L) and EM-2 (1 μmol/L)remarkably reduced the frequency but not the amplitude of miniature excitatory postsynaptic currents (mEPSCs) and miniature inhibitory postsynaptic currents (mIPSCs). These effects were antagonized by 3-funaltrexamine ( β-FNA, 10 μmol/L), a selective μ-opioid receptor antagonist. Noticeably, EM-1 showed higher potency in decreasing the frequency of mEPSCs and mIPSCs than that of EM-2. These results indicate that EMs suppress both excitatory and inhibitory synaptic transmission by activating presynaptic μ-opioid receptors in the SG and EM-1, compared with EM-2, might be a more potent endogenous analgesic at the spinal cord level.

Objective:This study aims to investigate the anxiety-like behavior induced by cystitis and its neurobio-logical mechanisms in the anterior cingulate cortex(ACC)by constructing a mouse model of cystitis.Methods:A cys-titis model was established using lipopolysaccharide(LPS).Anxiety-like behavior in mice was explored through the open field test,and single-nucleus RNA sequencing was used to analyze changes in gene expression of neurons in the ACC.Results:HE staining results indicated significant inflammatory responses in the bladders of LPS-treated mice,including extensive infiltration of inflammatory cells,tissue edema,and bladder epithelial shedding.The open field test showed that the time and distance of mice moving in the central area of the open field were significantly reduced,indica-ting obvious anxiety-like behavior.Quality control of single-nucleus sequencing data suggested good data quality.Di-mensionality reduction clustering of the top 2000 highly variable genes revealed seven different cell subpopulations in the ACC.Five major cell types were identified in the ACC,and neurons were further clustered into five different subpopula-tions,identifying two main cell types.Differential gene analysis indicated significant changes in gene expression in neu-rons,with functional enrichment in pathways related to synaptic dysfunction.Conclusion:Cystitis can induce changes in gene expression in specific cell subpopulations in the ACC,suggesting that neurons may play an important role in the anxiety-like behavior induced by cystitis.This provides a new perspective for understanding the relationship between cystitis and anxiety behavior and offers important experimental evidence for future exploration of the brain regions and molecular mechanisms underlying cystitis-induced anxiety behavior.