INTRACEREBROVENTRICULAR INJECTION OF RENIN IN THE NEONATAL RAT REVEALS A PRECOCIOUS SODIUM APPETITE THAT IS DISSOCIATED FROM RENIN-AROUSED THIRST

Previous research on the ontogeny of sodium appetite in the rat has sh own that sodium deficit first engenders sodium intake at 12 days of ag e, whereas direct stimulation of the brain renin-angiotensin system by intracranial injection of renin increases intake of NaCl solution as early as 3 days postnatally. Similar activation of brain angiotensin a lso increases thirst, so that the specificity of the precocious sodium intake remains undetermined. In this article we report experiments th at dissociate neonatal renin-evoked sodium appetite and thirst, and es tablish the specificity of the appetite. Our findings confirm that sod ium appetite can first be discerned at 3 days of age, and show that it rapidly develops until 12 days of age. During this developmental wind ow, renin-evoked sodium appetite is dissociated from thirst because (a ) NaCl is preferred to water, (b) the appetite develops faster than th irst, and (c) 3-day-old renin-stimulated pups will avidly lick dry NaC l. These results show that activation of brain angiotensin in the 3-da y-old rat pup evokes a precocious and specific sodium appetite. (C) 19 94 John Wiley and Sons, Inc.