Endocrinology, Vol 137, 1745-1751, Copyright © 1996 by Endocrine Society

ARTICLES

Constitutive nitric oxide synthase in hypothalami of normal and hereditary diabetes insipidus rats and mice: role of nitric oxide in osmotic regulation and its mechanism

H Wang and JF Morris
Department of Human Anatomy, University of Oxford, United Kingdom.

Constitutive nitric oxide synthase (cNOS) was immunolocalized to study its role in osmotic regulation. Immunoreactivity was observed in all major hypothalamic osmoregulatory structures, the organum vasculosum laminae terminalis, subfornical organ, median preoptic nucleus, and supraoptic and paraventricular nuclei. These nuclei were compared in normal Long-Evans rats and homozygous Brattleboro rats with hereditary hypothalamic diabetes insipidus and in normal mice and mice with hereditary nephrogenic diabetes insipidus. About 50% of supraoptic neurons in Long-Evans rats and 90% in Brattleboro rats were cNOS immunopositive; a qualitatively similar difference occurred in the paraventricular nucleus. Mice with hereditary nephrogenic diabetes insipidus also showed a greater proportion of cNOS-positive supraoptic neurons (50%) than normal mice (20%). However, the number of cNOS- positive cells in the organum vasculosum laminae terminalis, subfornical organ, and median preoptic nucleus dis not differ significantly between diabetic and normal animals. The similar changes in cNOS in two mutant strains in which the only common feature is chronic osmotic stimulation shows that differences in vasopressin and oxytocin are not involved in the regulation of cNOS. The results suggest strongly that cNOS is involved in long term modulation of the hypothalamo-neurohypophysial system and, hence, body water and electrolyte homeostasis, and that cNOS is itself regulated by body osmotic status.

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