We have previously shown that atrial natriuretic polypeptide is present in the brain with the highest concentration in the hypothalamus and septum and that intracerebroventricular injection of atrial natriuretic polypeptide inhibits water drinking induced by centrally injected angiotensin II or 24-hour water deprivation in rats. To study further the role of brain atrial natriuretic polypeptide in the control of water and electrolyte balance, the effect of chronic intracerebroventricular infusion of atrial natriuretic polypeptide on salt appetite in spontaneously hypertensive rats and normotensive Wistar-Kyoto rats was examined with a free-choice, two-bottle preference test. The intracerebroventricular infusion of 100 ng/hour and 400 ng/hour of α-human atrial natriuretic polypeptide preferentially suppressed the intake of 0.30 M NaCl solution and attenuated the elevated preference for the hypertonic saline in spontaneously hypertensive rats while centrally infused α-human atrial natriuretic polypeptide had no significant effects on drinking behavior in Wistar-Kyoto rats. Blood pressure did not change significantly throughout the experiment in either rat strain. It is concluded that the exaggerated salt appetite in spontaneously hypertensive rats is blunted by centrally administered atrial natriuretic polypeptide. Such an effect of atrial natriuretic polypeptide along with its antidipsogenic effect suggests that brain atrial natriuretic polypeptide plays a role in water and electrolyte homeostasis and in blood pressure control.
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