Effects of central and peripheral urocortin on fed and fasted gastroduodenal motor activity in conscious rats

Since few previous studies have examined the effects of urocortin on physiological fed and fasted gastrointestinal motility, we administered urocortin intracerebroventricularly (icv) or intravenously (iv) in freely moving conscious rats and examined the changes in antral and duodenal motility. Icv and iv injection of urocortin disrupted fasted motor patterns of gastroduodenal motility, which were replaced by fed-like motor patterns. When urocortin was given icv and iv in the fed state, the motor activity remained like the fed patterns but % motor index (%MI) was decreased in the antrum and increased in the duodenum. Increase in the %MI in the duodenum induced by urocortin was shown as a nonpropagated event, since the transit of nonnutrient contents in the duodenum was decreased by icv and iv injection of urocortin. Changes in the gastroduodenal motility induced by icv injection of urocortin were abolished in animals with truncal vagotomy but not altered in animals with mechanical sympathectomy, suggesting that the vagal pathway may mediate the central action of urocortin. Neither urocortin antiserum nor alpha-helical CRF-(9-41) affected fed and fasted gastroduodenal motility, suggesting that endogenous urocortin is not involved in regulation of basal gastroduodenal motility.