Microinjection of D-2-amino-7-phosphonoheptanoate into the dorsal periaqueductal gray matter reduces the pressor response to, glutamate injected at the same site

ABSTRACT

The current study assesses the influence of the N-methil-D-aspartate (NMDA) receptor antagonist D-2-amino-7-phosphonohepatanoate (AP7) on the pressor effect of glutamate microinjected into the dorsal periaqueductal gray matter (DPAG) of urethane-anesthetized rats. Glutamate (20, 40 and 80 nmol/site) caused dose-related reproducible increases in systolic and diastolic blood pressure. Microinjection of saline into the DPAG did not alter the pressor effects of glutamate (80 nmol/site). Similar pretreatment with AP7 (2nmol/site) significantly (P < 0.05) attenuated the pressor effects of glutamate from ñ26.5 ñ 7.0 to +3.4 ñ 3.3 mmHg (sistolic blood pressure). We conclude that the pressor efffect of glutamate in the DPAG is mediated largely by activation of NMDA receptors