Cardiovascular effects of noradrenaline microinjected into the dorsal periaqueductal gray area of unanaesthetized rats.
The periaqueductal grey area (PAG) is a mesencephalic region that is involved in the modulation of cardiovascular changes associated with behavioural responses. Among the neurotransmitters present in the PAG, noradrenaline (NA) is also known to be involved in central nervous system cardiovascular regulation. In the present study we report the cardiovascular effects of the microinjection of NA into the dorsal portion of the PAG (dPAG) of unanaesthetized rats and the peripheral mechanism involved in their mediation. Injection of NA in the dPAG of unanaesthetized rats evoked a dose-dependent pressor response accompanied by bradycardia. The magnitude of the pressor responses was higher at more rostral sites in the dPAG and decreased when NA was injected into the caudal portion of the dPAG. The responses to NA were markedly reduced in urethane-anaesthetized rats. The pressor response was potentiated by i.v. pretreatment with the ganglion blocker pentolinium and blocked by i.v. pretreatment with the vasopressin antagonist dTyr(CH2)5(Me)AVP. The results suggest that activation of noradrenergic receptors within the dPAG can evoke pressor responses, which are mediated by acute vasopressin release.
Pelosi
Gislaine Garcia
GG
Department of Pharmacology, School of Medicine of Ribeirão Preto, University of São Paulo, Avenue Bandeirantes 3900, 14040-900, Ribeirão Preto, São Paulo, Brazil.
Corrêa
Fernando Morgan Aguiar
FM
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D002320:Cardiovascular Physiological Phenomena / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D006339:Heart Rate / Q000187:drug effects; D007016:Hypophysectomy / Q000379:methods; D008297:Male; D008845:Microinjections / Q000379:methods; D018733:Nicotinic Antagonists / Q000494:pharmacology; D009638:Norepinephrine / Q000494:pharmacology*; D010425:Pentolinium Tartrate / Q000494:pharmacology; D010456:Peptides, Cyclic / Q000494:pharmacology; D010487:Periaqueductal Gray / Q000187:drug effects*; D051381:Rats; D017208:Rats, Wistar; D014443:Tyrosine / Q000031:analogs & derivatives / Q000494:pharmacology; D014851:Wakefulness / Q000187:drug effects*
D018733:Nicotinic Antagonists; D010456:Peptides, Cyclic; C433483:Tyr(Me)-AVP; D014443:Tyrosine; D010425:Pentolinium Tartrate; D009638:Norepinephrine