Impaired regulation of neurohypophyseal vasopressin secretion in rats treated neonatally with monosodium-L-glutamate.

Monosodium-L-glutamate (MSG) lesioning of the arcuate nucleus (ARC) was utilized to elucidate the importance of its dopaminergic system for regulation of neurohypophyseal vasopressin (AVP) secretion. Water deprivation in control animals elicited a rise in plasma AVP and depletion of neurohypophyseal AVP, at unchanged AVP contents of the paraventricular (PVN) and supraoptic (SON) nuclei. Dopaminergic activity was markedly stimulated in the PVN and ARC. Neonatal MSG treatment resulted in elevated plasma AVP levels at reduced neurohypophyseal AVP due to diminished dopaminergic input from the ARC. When MSG treated animals were subjected to dehydration, none of the changes in plasma/neurohypophyseal AVP and dopamine metabolism in the PVN and ARC observed in control animals were seen. These results suggest that the ARC plays an important role in the dopaminergic control of neurohypophyseal AVP secretion.