Centrally mediated cardiovascular responses to intracisternal injections of sympathomimetic amines in anesthetized rats.
The cardiovascular effects resulting from intracisternal (i.c.) injections of sympathomimetic amines were studied in alpha-chloralose-urethanized rats. Norepinephrine (0.5-5 mug i.c.) caused a typical rise in blood pressure with no significant change in heart rate and a fall in blood pressure with a bradycardia, which were completely blocked after treatment with phentolamine (10-50 mug i.c.) L-isoproterenol (0.05-0.5 mug i.c.) and trimetoquinol (0.5-3 mug i.c.), a beta-sympathomimetic agent, usually caused a fall in blood pressure with a tachycardia, which was reduced after treatment with propranolol (10-50 mug i.c.), but trimetoquinol was inclined to cause a rise in blood pressure with a tachycardia. Epinephrine (5 mug i.c.) showed both centrally mediated alpha- and beta-sympathomimetic effects. Tyramine (0.5-1 mg i.c.) caused mixed blood pressure responses presumably due to a release of norepinephrine and epinephrine, and these responses were partially blocked after treatment with phentolamine (100 mug i.c.) or propranolol (50 mug i.c.). These observations suggest that both alpha- and beta-sensitive adrenergic zones may exist on the vasomotor center of the pons and medulla in rats, and both norepinephrine and epinephrine might centrally play a physiological role as the neurotransmitters controlling blood pressure in rats.
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D002946:Cisterna Magna; D004837:Epinephrine / Q000494:pharmacology; D006439:Hemodynamics / Q000187:drug effects*; D007267:Injections; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D009638:Norepinephrine / Q000494:pharmacology; D051381:Rats; D013566:Sympathomimetics / Q000008:administration & dosage / Q000494:pharmacology*; D014213:Tretoquinol / Q000494:pharmacology; D014439:Tyramine / Q000494:pharmacology
D013566:Sympathomimetics; D014213:Tretoquinol; D007545:Isoproterenol; D009638:Norepinephrine; D014439:Tyramine; D004837:Epinephrine