Cardiovascular responses to noradrenaline microinjection in the ventrolateral periaqueductal gray of unanesthetized rats.
The periaqueductal gray area (PAG) is a mesencephalic area involved in cardiovascular modulation. Noradrenaline (NA), a neurotransmitter involved in central blood pressure control, is present in the rat PAG. We report here on the cardiovascular effects caused by NA microinjection into the ventrolateral PAG (vlPAG) of unanesthetized rats and the peripheral mechanism involved in their mediation. NA microinjection in the vlPAG of unanesthetized rats evoked dose-related pressor and bradycardiac responses. No significant cardiovascular responses were observed in urethane-anesthetized rats. The pressor response was potentiated by pretreatment with the ganglion blocker pentolinium (5 or 10 mg/kg, intravenously). Pretreatment with the vasopressin antagonist dTyr(CH2)5 (Me)AVP (50 microg/kg, intravenously) blocked the pressor response evoked by the NA microinjection into the vlPAG. Additionally, circulating vasopressin content was found to be significantly increased after NA microinjection in the vlPAG. The results suggest that activation of noradrenergic synapses within the vlPAG modulates vasopressin release in unanesthetized rats.
Pelosi
Gislaine Garcia
GG
Department of Pharmacology, School of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto, São Paulo, Brazil.
Tavares
Rodrigo Fiacadori
RF
Antunes-Rodrigues
José
J
Corrêa
Fernando Morgan Aguiar
FM
D018686:Anesthetics, Intravenous; D000818:Animals; D001127:Arginine Vasopressin / Q000008:administration & dosage / Q000031:analogs & derivatives / Q000494:pharmacology; D001794:Blood Pressure / Q000187:drug effects; D002319:Cardiovascular System / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D004334:Drug Administration Schedule; D004357:Drug Synergism; D005730:Ganglionic Blockers / Q000008:administration & dosage / Q000494:pharmacology; D006339:Heart Rate / Q000187:drug effects; D006727:Hormone Antagonists / Q000008:administration & dosage / Q000494:pharmacology; D007275:Injections, Intravenous; D008297:Male; D008845:Microinjections; D009638:Norepinephrine / Q000008:administration & dosage* / Q000037:antagonists & inhibitors / Q000494:pharmacology; D010425:Pentolinium Tartrate / Q000008:administration & dosage / Q000494:pharmacology; D010487:Periaqueductal Gray; D051381:Rats; D017208:Rats, Wistar; D014520:Urethane; D014662:Vasoconstrictor Agents / Q000008:administration & dosage* / Q000037:antagonists & inhibitors / Q000494:pharmacology; D014667:Vasopressins / Q000037:antagonists & inhibitors / Q000097:blood
D018686:Anesthetics, Intravenous; D005730:Ganglionic Blockers; D006727:Hormone Antagonists; D014662:Vasoconstrictor Agents; D014667:Vasopressins; D001127:Arginine Vasopressin; D014520:Urethane; C025043:vasopressin, 1-(1-mercaptocyclohexaneacetic acid)-2-(O- methyl-L-tyrosine)-8-L-arginine-; D010425:Pentolinium Tartrate; D009638:Norepinephrine