Cardiovascular responses to glutamate microinjection in the dorsomedial periaqueductal gray of unanesthetized rats.
The periaqueductal gray area (PAG) is a mesencephalic area involved in cardiovascular modulation. Glutamate (L-Glu) is an abundant excitatory amino acid in the central nervous system (CNS) and is present in the rat PAG. Moreover, data in the literature indicate its involvement in central blood pressure control. Here we report on the cardiovascular effects caused by microinjection of L-Glu into the dorsomedial PAG (dmPAG) of rats and the glutamatergic receptors as well as the peripheral mechanism involved in their mediation. The microinjection of L-Glu into the dmPAG of unanesthetized rats evoked dose-related pressor and bradycardiac responses. The cardiovascular response was significantly reduced by pretreatment of the dmPAG with a glutamatergic M-methyl-D-aspartate (NMDA) receptor antagonist (LY235959) and was not affected by pretreatment with a non-NMDA receptor antagonist (NBQX), suggesting a mediation of that response by the activation of NMDA receptors. Furthermore, the pressor response was blocked by pretreatment with the ganglion blocker pentolinium (5 mg/kg, intravenously), suggesting an involvement of the sympathetic nervous system in this response. Our results indicate that the microinjection of L-Glu into the dmPAG causes sympathetic-mediated pressor responses in unanesthetized rats, which are mediated by glutamatergic NMDA receptors in the dmPAG.
Department of Pharmacology School of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto, São Paulo, Brazil. pelosigg@gmail.com
Gislaine Garcia
GG
Pelosi
Cristiane
C
Busnardo
Rodrigo Fiacadori
RF
Tavares
Fernando Morgan Aguiar
FM
Corrêa
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D002319:Cardiovascular System / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D018698:Glutamic Acid / Q000008:administration & dosage*; D006339:Heart Rate / Q000187:drug effects; D008297:Male; D008845:Microinjections; D010487:Periaqueductal Gray / Q000187:drug effects*; D051381:Rats; D017208:Rats, Wistar
D018698:Glutamic Acid