GASTRIC-EMPTYING AND GASTRIC-INTESTINAL TRANSIT IN RATS WITH VARYING OVARIAN HORMONE STATUS

Basal and stimulated gastric emptying and gastrointestinal (GI) transi t in rats of varying ovarian hormone status were compared to define di rect ovarian hormone effects on GI function. Thyrotropin-releasing hor mone (TRH) was used to evoke vagal GI motility stimulation. Adult fema le Sprague-Dawley rats were anesthetized (equithesin), ovariectomized, and implanted with 28-day estrogen (E), progestrone (P), E+P, or vehi cle (V) pellets; males were also studies. On Day 26, fasted rats were anesthetized (urethane). Nonabsorbable C-14 polyethylene glycol-4000 i n saline was gavaged at t = 0. At t = 5 minutes, TRH or saline was adm inistered intracisternally. At t = 30 or 60 minutes, the GI tract was removed, ligated, sectioned, and counted. Gastric emptying was express ed as 100% minus the ration of gastric to total counts; GI transit was expressed as geometric center of radioactivity. In saline-treated rat s, gastric emptying and GI transit at 60 minutes varied significantly among ovarian hormone-treated groups, with E lower and males elevated. TRH significantly increased both variables at both times in all group s. Results are consistent with acceleration of upper GI function in th e absence of E, possibly contributing to GI symptoms during menopause and late luteal phase.