The effect of intracerebroventricular (i.c.v.) injection of synthetic rat atrial natriuretic polypeptide (alpha-rANP) on drinking behavior was studied in normotensive rats, alpha-rANP (0.2, 0.4 or 0.8 micrograms in 5 microliter) caused a dose-dependent dipsogenic effect which was abated by i.c.v. pretreatment with saralasine (9 micrograms in 5 microliter). These results suggest that alpha-rANP possesses dipsogenic effects in water repleted rats and that brain angiotensin is involved. In addition, our data indicate that, at least as far as the effect of cerebral ANP is concerned, there are some differences between alpha-rANP and human atrial natriuretic polypeptide.