Sexually dimorphic response of colorectal motility to noxious stimuli in the colorectum in rats.

This study showed a remarkable sex difference in responses of colorectal motility to noxious stimuli in the colorectum in rats: colorectal motility was enhanced in response to intracolonic administration of a noxious stimulant, capsaicin, in male rats but not in female rats. The difference in descending neurons from the brain to spinal cord operating after noxious stimulation would be responsible for the sex difference. In male rats, serotoninergic and dopaminergic neurons are dominantly activated, both of which activate the spinal defaecation centre. In female rats, GABAergic neurons in addition to serotoninergic neurons are activated. GABA may compete for facilitative action of 5-HT in the spinal defaecation centre, and thereby colorectal motility is not enhanced in response to intracolonic administration of capsaicin. The findings provide a novel insight into pathophysiological mechanisms of sex differences in functional defaecation disorders such as irritable bowel syndrome (IBS). ABSTRACT: We previously demonstrated that noxious stimuli in the colorectum enhance colorectal motility through activation of descending pain inhibitory pathways in male rats. It can be expected that the regulatory mechanisms of colorectal motility differ in males and females owing to remarkable sex differences in descending pain inhibitory pathways. Thus, we aimed to clarify sex differences in responses of colorectal motility to noxious stimuli in rats. Colorectal motility was measured ...
Source: The Journal of Physiology - Category: Physiology Authors: Tags: J Physiol Source Type: research