Effects of aldosterone and dexamethasone on atrial natriuretic peptide levels in preoptic and hypothalamic nuclei of adrenalectomized and intact rats.

The effect of aldosterone and dexamethasone on the concentrations of atrial natriuretic peptide (ANP) in preoptic and hypothalamic nuclei was examined in adrenalectomized and intact rats. Five days after adrenalectomy, increased ANP levels in those brain areas which control water intake, i.e. in the subfornical organ, supraoptic nucleus, and in the so-called hypothalamic drinking centers (perifornical nucleus, lateral hypothalamic area) were measured. In contrast to this, adrenalectomy decreased ANP levels markedly in the organum vasculosum laminae terminalis and preoptic periventricular nucleus, which are reportedly involved in the central regulation of salt and water homeostasis. ANP contents of these two preoptic structures were restored almost completely by daily administration of 0.9% sodium chloride or aldosterone but not dexamethasone. The daily administration of aldosterone elevated ANP levels in the supraoptic, paraventricular and perifornical nuclei as well as in the lateral hypothalamus both in control and adrenalectomized rats. Dexamethasone which was without any significant effect on preoptic and hypothalamic nuclei in control rats elevated ANP levels in the supraoptic and perifornical nuclei and in the lateral hypothalamic area of adrenalectomized animals. Since neither adrenalectomy, nor aldosterone or dexamethasone treatment influenced plasma ANP levels, altered ANP contents measured in preoptic and hypothalamic nuclei may represent a direct effect of adrenal corticoids (mainly aldosterone) on brain ANP-containing neurons which may participate in the control of body fluid and electrolyte homeostasis.