Enhanced pressor responses to ICV vasopressin after pretreatment with oxytocin.
The role of oxytocin (OT) in the modulation of arginine vasopressin (AVP)-induced cardiovascular effects within the central nervous system was investigated in urethan-anesthetized rats. Intracerebroventricular injection of AVP (1-10 pmol) produced dose-dependent increases in mean arterial pressure (MAP) and heart rate (HR). These responses were enhanced in rats pretreated 24 h earlier with OT (10 pmol icv). The enhanced cardiovascular effects of AVP in OT-pretreated animals were dose dependent, blocked by the V1 antagonist d(CH2)5Tyr(Me)AVP, not evoked by OT alone, and occurred in the absence of changes in basal (nonstimulated) MAP and HR. In addition, central administration of AVP in OT-pretreated rats, but not in saline-pretreated controls, caused dose-dependent oscillations of the MAP and HR responses and, at higher doses, death of the animals. The enhanced cardiovascular actions of centrally injected AVP in OT-pretreated rats do not appear to be secondary to skeletal muscle contractions or the result of cerebral ischemia. Our data point to an interaction between the central oxytocinergic and vasopressinergic systems in cardiovascular control.
Poulin
P
P
Neuroscience Research Group, University of Calgary, Alberta, Canada.
Komulainen
A
A
Takahashi
Y
Y
Pittman
Q J
QJ
D000818:Animals; D001127:Arginine Vasopressin / Q000008:administration & dosage / Q000031:analogs & derivatives / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D001794:Blood Pressure / Q000187:drug effects*; D001921:Brain / Q000098:blood supply; D002545:Brain Ischemia / Q000503:physiopathology; D002552:Cerebral Ventricles / Q000187:drug effects / Q000502:physiology*; D002560:Cerebrovascular Circulation / Q000187:drug effects; D006339:Heart Rate / Q000187:drug effects*; D007276:Injections, Intraventricular; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology; D010121:Oxytocin / Q000008:administration & dosage / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012039:Regional Blood Flow / Q000187:drug effects
D001127:Arginine Vasopressin; D010121:Oxytocin; C025043:vasopressin, 1-(1-mercaptocyclohexaneacetic acid)-2-(O- methyl-L-tyrosine)-8-L-arginine-