Postnatal MSG treatment attenuates angiotensin II (AII) induced drinking in rats

Exogenous angiotensin II (AII) administration produces a robust drinking response, even in water-satiated rats. All receptors are located in the hypothalamus and circumventricular organs (CVOs). Early postnatal administration of monosodium glutamate (MSG) produces hypothalamic/CVO damage. Therefore MSG might damage hypothalamic/CVO neurons important for producing the drinking response to AII. Few noninvasive procedures or tests exist to indicate the presence of a MSG lesion. Thus, the present study sought to determine whether altered water consumption after AII administration would signify the presence of a MSG lesion, as well as to demonstrate hypothalamic/CVO involvement in AII-induced drinking. Adult rats (dosed as neonates with MSG or saline) were given various doses of AII and the beta-adrenergic agonist isoproterenol. MSG-treated rats drank significantly less water after 100 ug/kg, sc AII than control rats. MSG-treated rats also had an unexpectedly high mortality after 100 ug/kg, sc isoproterenol. Thus, measurement of the drinking response may be a sensitive, noninvasive method for detecting neurotoxic damage to hypothalamic/CVO sites critical for the central action of AII.