Neural pathways mediating drinking and feeding in rats

Abstract

Drinking and feeding were elicited by stimulation of topographically differentiated sites in the rat brain. When stimulated with low current via small electrodes, drinking was elicited from the zona incerta (ZI) feeding from the lateral hypothalamus (LH), and both responses from a restricted portion of the LH dorsolateral to the fornix. With stimulation of sites outside these regions consummatory responses occurred unreliably. Discrete lesions were made at sites of stimulation and resulting axonal degeneration was stained by the Fink and Heimer technique. Although similar connections existed, the main degeneration from drinking sites in the ZI differed from that arising from feeding sites in LH; degeneration from drinking sites coursed in the ZI and in other structures including the nucleus reuniens, ventromedial thalamus, the region ventral to the globus pallidus and the region near the subcommissural organ; degeneration from feeding sites in the LH coursed in the medial forebrain bundle and in the pathways that extend from it. Degeneration from sites dorsolateral to the fornix where both feeding and drinking were elicited was similar to that from feeding sites. These anatomical differences and similarities suggest the existence of two neural systems for drinking, one being closely related to the system for feeding and the other being independent.