ACTIVATION OF P-2-PURINOCEPTORS IN THE NUCLEUS-TRACTUS-SOLITARIUS MEDIATE DEPRESSOR RESPONSES

The purpose of the study was to examine the role of P-2 purinergic rec eptors in mechanisms of cardiovascular control mediated by the nucleus tractus solitarius (NTS), a major integrative site in the brainstem i nvolved in the reflex coordination of cardiorespiratory and visceral r esponse patterns. Microinjections of ATP and its analogues were made i nto the subpostremal NTS of anesthetized, spontaneously breathing rats . ATP, alpha/beta-methylene ATP (alpha beta-meATP) and 2-methylthio-AT P (2-meSATP) produced significant dose-related reductions in arterial blood pressure. alpha beta-meATP was slightly more potent than ATP and 2-meSATP. Pretreatment with the P-2 receptor antagonist, suramin (0.5 nmol/rat), into the same NTS site 10 min prior to agonist administrat ion completely blocked pronounced depressor response pattern elicited by the highest dose of alpha beta-meATP (0.1 nmol/rat). The present fi ndings suggest that endogenous ATP may serve as a fast transmitter sub stance in NTS-mediated mechanisms of cardiovascular control.