Effect of L-glutamate, injected into the posterior hypothalamus, on blood pressure and heart rate in unanesthetized and unrestrained rats.

In unanesthetized and unrestrained rats, microinjection of L-glutamate into the posterior hypothalamus produced hypertension and tachycardia. These cardiovascular responses were mostly accompanied with behavioral excitation such as searching the cage, rearing and sniffing. The cardiovascular responses elicited by L-glutamate were attenuated by prior injection with propranolol and hexamethonium but not with glutamate diethylester, phentolamine and atropine. The behavioral responses to L-glutamate were suppressed by propranolol, hexamethonium and phentolamine. These results suggest that catecholaminergic and/or cholinergic systems in the posterior hypothalamus may be involved in the mediation of the cardiovascular and behavioral responses induced by L-glutamate.