Effects Of Ovarian Hormone On 5-HT3 Receptors In The Dorsal Root Ganglion Of Rats With Visceral Hypersensitivity

AIM: It has been proved that women have a higher prevalence of irritable bowel syndrome (IBS), and its mechanism underlying pathophysiology is not known. In this paper we studied the effects of ovarian hormone on 5-HT3 receptors in the colon and dorsal root ganglion of rats with visceral hypersensitivity, and explore the role of ovarian hormone on female patients with irritable bowel syndrome.Methods: Neonatal female Sprague-Dawley rats received mechanical colo-nic irritation between postnatal days 8 and 21, the intensity of stimulation is 60mmHg and each activation lasts 1 minute. The distension was repeated 2 times within an hour. The rats were randomly divided into three groups of 16 each when they grew up to 2 months old: A: shame operation (sham), B: ovariectomy (OVX) C: overiectomy with estrogen (E2) and progesterone (P) replacement therapy (OVX+ E2+ P),group Sham were excised 1g fat and the bilateral ovariectomy of the other two groups were ligated below the ovaries, which were then excised.After 1 week interruption ,give estradiol benzoate(EB)5 u g per day and progesterone 0.2mg per day subcutaneously to group C and the other two groups were giving the same peanut oil injection.The abdominal withdrawal reflex (AWR) were recorded and the fecal habits were observed four weeks after operation. The expression of 5-HT3 receptors were examined by RT-PCR and immunohistochemical staining.Results: Behavior study showed: OVX+ E2+ P group rats showed a significant decrease endurance with colonic irritation (P<0.01). Colon histology: There were no obvious damnification and interstitial edema in the slices. Compare with the other two groups;OVX+ E2+ P group rats showed increase in fecal pellets and decrease in the time of vitreous pellets excretion. Immunohistochemical staining: the color of OVX+ E2+ P group rats slices were deeper than the other two groups (P<0.01). mRNA expression: OVX+ E2+ P group rats express significant higher 5-HT3 receptors in dorsal root ganglion (P<0.01).Conclusions: The persistent visceral pain to neonatal rats can indeed result in chronic visceral hypersensitivity that persists through adulthood despite the absence of any identifiable histopathology. Ovarian hormone aggravates visceral hypersensitivity in rats and increase 5-HT3 receptors levels in rats colon and dorsal root ganglion.