Fourth ventricle injection of corticotropin-releasing factor and gastric emptying of glucose during gastric fill.

The effect of corticotropin-releasing factor (CRF) administered into the fourth ventricle on the gastric emptying of a 12-ml intragastric infusion of 12.5% D-glucose was examined in nondeprived male rats. All three CRF doses tested (10, 100, and 1,000 pmol) significantly reduced (by 28, 29, and 44%, respectively) the amount of glucose emptied from the stomach at the end of the 12-min (1.0 ml/min) gastric infusion interval. The 10 pmol effective dose is the lowest yet reported to influence gastric emptying. The receptor specificity of the exogenous CRF (1,000 pmol) effect was demonstrated by its complete blockade by preinjection of alpha-helical CRF-9-41 (10 nmol) into the fourth ventricle. Injection of the antagonist alone, however, did not affect glucose emptying, indicating little activation of the targeted receptors under the present nonstressful, baseline conditions. Our results suggest that of the central CRF receptor systems that influence gastric emptying, those in the caudal brain stem, targeted by fourth ventricular injection, may be of particular importance.