A comparison of synthetic human and rat ANP administered intracerebroventricularly in freely moving normotensive and hypertensive rats.

The effects of intracerebroventricular (i.c.v.) injection of alpha-human atrial natriuretic peptide (alpha-hANP) and alpha-rat atrial natriuretic peptide (alpha-rANP) were studied in normotensive [Wistar-Kyoto (WKY)] and spontaneously hypertensive rats (SHR). Intracerebroventricular injection of alpha-hANP (200, 400, and 800 ng in 5 microliters) did not modify mean arterial pressure (MAP), heart rate (HR), and water intake in both WKY rats and SHR. On the contrary, alpha-rANP (200, 400, and 800 ng in 5 microliters) caused strong dipsogenic, pressor, and bradycardic effects that were greater in hypertensive than in normotensive rats. Saralasin (9 microns in 5 microliters), injected 2 min prior to alpha-rANP, abated these effects, thus indicating an involvement of brain angiotensin. Our results suggest that, at least as far as the cerebral effects of ANP are concerned, some difference exists between alpha-rANP and human atrial natriuretic peptide.

Central dipsogenic effect of synthetic rat atrial natriuretic polypeptide in normotensive rats.

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.