A STUDY ON THE VASOPRESSIN-INDUCED DELAY IN THE GASTROINTESTINAL TRANSIT IN MICE - POSSIBLE MECHANISM OF ACTION

The effect of arginine vasopressin (AVP) on the gastrointestinal (GI) transit and its possible mechanism were studied using charcoal meal te st in mice. A dose related inhibitory effect was recorded. The effect appears to be independent of the time allowed between AVP administrati on and testing. The studies on the mechanism reveal that AVP acts with out involving V1 and V2 vasopressin receptors.An almost complete rever sal of the effect by physostigmine and potentiation by atropine indica te that AVP might act through an inhibition of the release of acetylch oline. However, the neural nicotinic receptors mechanisms do not seem to contribute since hexamethoinium falied to modify the AVP action. Fu rther, a partial antagonism by naloxone or prazosin pretreatment indic ates that opioid and alpha1 adrenergic systems also contribute to this action of AVP. However, the effect appeares to be independent of alph a2 and beta Adrenergic systems since yohimbine and propranolol failed to modify the same.