Effects of subdiaphragmatic vagotomy on schedule induced drinking and schedule dependent lever pressing

Abstract

Fourteen male albino rats reduced in body weight were exposed to a daily 1 hr FI-1 min schedule of food reinforcement. When schedule induced licking and drinking and schedule dependent lever pressing stabilized, seven animals were subjected to bilateral subdiaphragmatic vagus nerve transections and the other seven animals were subjected to sham operations. Changes in licking, drinking, and lever pressing were assessed when animals were reduced to 80% of their initial body weight by partial food deprivation and when body weights recovered after the animals were returned to conditions of ad lib feeding. Results indicate that vagotomy produces a significant decrease in schedule induced licking and drinking when animals are at reduced body weight. When vagotomized rats are allowed to recover body weight due to ad lib feeding, lever presses decrease but licking and drinking are not further reduced. The sham operation had no appreciable effects at reduced body weight. When allowed to recover body weight sham animals exhibited significant decreases in licking, drinking, and lever pressing. In addition, the rate of body weight gain and home cage food and water consumption and water consumed in response to hypertonic saline injections were reduced in vagotomized animals when allowed to feed ad lib. Results are discussed in terms of vagal afferent activity from the viscera to the lateral hypothalamus associated with food deprivation and body weight reduction and the maintenance of adjunctive behavior.