Gastric Motility in Rats with Varying Ovarian Hormone Status

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Abstract
Gastrointestinal (GI) symptoms suggestive of altered motility vary with menstrual cycle phase and menopause, but the effects of ovarian hormones on gastric motility have not been described. Basal and stimulated gastric motility were studied in male and female rats that were ovariectomized and implanted with continuous-release progesterone and/or estrogen pellets. Following 26 days of hormone treatment, rats were implanted with a gastric tension transducer. Contractile activity was recorded, then thyrotropin-releasing hormone (TRH) or saline was injected intracisternally and motility was monitored. An index was calculated based on frequency and amplitude; response to TRH was expressed as percentage of the basal index. Basal contraction frequency was highest in the estrogen and estrogen + progesterone groups. Hormone treatment significantly affected the TRH-stimulated motility index; TRH induced increased motility in all groups, with larger, more sustained responses in vehicle, progesterone, and male groups. Results demonstrate the ovarian hormone modulation of basal and stimulated gastric motility. Such modulation may contribute to changes in GI symptoms with altering ovarian hormone state.