HYPOTHALAMIC PARAVENTRICULAR NUCLEUS INVOLVEMENT IN THE PRESSOR RESPONSE TO N-METHYL-D-ASPARTIC ACID IN THE PERIAQUEDUCTAL GREY-MATTER

The aim of this study was to demonstrate paraventricular hypothalamic nucleus (PVN) involvement in the cardiovascular changes induced by N-m ethyl-d-aspartic acid (NMDA) microinjections at the level of periaqued uctal grey (PAG) matter. The study was carried out in anaesthetized ra ts and the arterial blood pressure monitored by a polygraph. NMDA inje ctions (0.68-6.8 nmol/rat) into the PAG area induced a significant inc rease in blood pressure. After pretreatment by injection of the NMDA r eceptor antagonist dl-2-amino-5-phosphonovaleric acid (2-APV, 0.05-5 n mol/rat) into the PVN, administration of NMDA (0.68 nmol/rat) into the PAG area elicited a decrease, rather than an increase, of blood press ure. We observed a significant reduction of the presser effect induced by 6.8 nmol/rat NMDA after 2-APV injection into the PVN. 2-APV inject ion into the dorsomedial hypothalamic nucleus, an area near the PVN, d id not modify the increase in blood pressure induced by NMDA in the PA G area. We suggest the existence of a glutamatergic connection between the PAG area and the PVN in the cardiovascular effects of NMDA.