Reduction of 125I-angiotensin II binding sites in rat brain following monosodium glutamate treatment.

Adult Sprague-Dawley rats were pretreated with 6 g/kg of monosodium glutamate (MSG). After one month, specific binding of 125I-angiotensin II was measured in membrane preparations from the brain. A 40-45% decrease in the number of 125I-angiotensin II binding sites was observed in brain tissues containing circumventricular organs. No decrease in binding sites was observed in the thalamus/hypothalamus brain region, which resides totally within the blood-brain barrier. The results suggest that MSG can destroy angiotensin-sensitive neurons in circumventricular structures, which are located primarily outside the blood-brain barrier.