Sex-dependent regulation of cholinergic responses in the mouse colon: functional evidence for reduced acetylcholinesterase-dependent control and nitrergic modulation in females.

Despite the higher incidence of diseases affecting the digestive tract among women, sex-related differences in gastrointestinal motility remain poorly investigated. This study compared the contractile and relaxant effects of cholinergic, adrenergic, and dopaminergic stimuli across major gastrointestinal segments of mice. For this, female and male Swiss mice (3-4 months old) were anesthetized and euthanized for isolation of gastric corpus strips (~ 0.5 cm length) and segments (~ 1.5 cm length) of the jejunum, ileum, and colon (n ≥ 6/group), which were mounted in organ baths under resting tension of 0.5 g. Spontaneous activity and responses to cumulative or noncumulative concentrations (100 pM-300 µM) of acetylcholine (ACh), carbamylcholine (CCh), norepinephrine (NOR), isoprenaline (ISO), and dopamine (DA) were recorded. Additionally, responses to electrical field stimulation (EFS; 20 V, 1 ms, 1-128 Hz, 10 s) were assessed in colonic segments before and after incubation with 1 µM neostigmine or 100 µM L-NAME. Although only slight sex-associated differences were found for the effects of NOR, ISO, DA, or ACh in the gastric corpus, jejunum, and ileum, the colon of female mice was hyperresponsive to ACh, but not to CCh. Furthermore, compared with male preparations, colonic segments from female mice displayed enhanced contractile responses and reduced relaxation following EFS. EFS-induced contractions were more sensitive to neostigmine and L-NAME in preparations from male mice. In conclusion, reduced acetylcholinesterase and nitrergic activity contribute to the enhanced cholinergic responses in the female colon, providing mechanistic insight into sex differences in gastrointestinal motility.