Impairment in fluid ingestion in rats with lesions of the zona incerta

Abstract

Rats with lesions of the zona incerta (ZI) dorsal to the lateral hypothalamus drink as much water as controls following intracellular or extracellular dehydration but restrict their daily water intake to minimal requirements for fluid balance, suggesting a specific impairment in secondary drinking. Following water deprivation, however, rats with ZI lesions responded to changes in palatability of the water as if they were experiencing slightly greater difficulty or aversiveness in drinking than controls. The cause appears to be an impairment in the ability to lick fluids from a spout. When water was available ad libitum or when water or liquid diet were provided after water or food deprivation, rats with ZI damage were unable to obtain as much fluid per lick as controls. It is concluded that lesions in this region of the brain impair the motor act of drinking and that the subsequent reduction in the efficiency of drinking is the cause of the attenuation of excessive water intake.