Aproteic diet decreases hypothalamic catecholamine turnover in adult male rats

Previous reports indicate that malnutrition reduces reproductive functions. We have demonstrated that protein deprivation in the diet also causes repr oductive dysfunction by reducing hypothalamic GnRH secretion. Noradrenaline and nitric oxide are modulators of GnRH secretion. Noradrenaline stimulate s GnRH secretion and nitric oxide inhibits catecholamine release. This work studies the hypothalamic catecholaminergic and nitrergic neuron activity i n Wistar adult male rats fed on an aproteic diet (AP) during 21 days; this treatment was started when rats were 70 days old. Our first experiment stud ied catecholamine turnover rate after inhibition of tyrosine hydroxylase ac tivity by injecting (i.p.) 400 mg/kg alpha-methyl-p-tyrosine. Our second ex periment studied in vitro hypothalamic nitric oxide synthase (NOS) activity in animals under the same diet. AP diet significantly decreased both norad renaline (P < 0.05) and dopamine (P < 0.05) hypothalamic turnover rate. Nor adrenaline turnover in cerebral cortex was not altered by the aproteic diet . However, hypothalamic NOS activity was not affected in animals fed on an AP diet. These results indicate that the lack of protein in the diet reduce s catecholaminergic neuron activity in adult male rats by a NO-independent mechanism, thus suggesting that a decrease in noradrenergic activity may be involved in the reduction of GnRH secretion induced by an AP diet. (C) 200 0 Elsevier Science B.V. All rights reserved.