Involvement of central alpha-pressor and beta-depressor adrenoceptors in the cardiovascular response to intracerebroventricular catecholamines in the rat.
Microinjections of catecholamines were performed into the lateral ventricle of anesthetized and unanesthetized rats and the blood pressure effects recorded prior to or after the administration of pharmacological antagonists. Injections of 20-100 micrograms normetanephrine (alpha-agonist) produced only pressor responses in both groups of animals. Injections of 10-20 micrograms of norepinephrine (preferentially an alpha-agonist) produced mainly pressor in awake and only depressor responses in anesthetized animals, whereas injections of 10-20 micrograms of epinephrine (preferentially a beta-agonist) produced only depressor responses in both groups of animals. Intracerebroventricular pretreatment with the beta-blocker propranolol (40-100 micrograms) blocked the depressor responses to the catecholamines or even reverted them into clear pressor response. Pretreatment with the alpha-blocker phentolamine (100 micrograms) reduced the pressor effects induced by the intraventricular injection of catecholamines. The existence of central alpha-pressor and beta-depressor mechanisms mediating the blood pressure responses to the intracerebroventricular administration of catecholamines is proposed.
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects*; D002395:Catecholamines / Q000008:administration & dosage / Q000494:pharmacology*; D002552:Cerebral Ventricles / Q000187:drug effects; D004837:Epinephrine / Q000494:pharmacology; D007276:Injections, Intraventricular; D008297:Male; D009638:Norepinephrine / Q000494:pharmacology; D009647:Normetanephrine / Q000494:pharmacology; D010643:Phenoxybenzamine / Q000494:pharmacology; D010646:Phentolamine / Q000494:pharmacology; D011433:Propranolol / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D011942:Receptors, Adrenergic, alpha / Q000502:physiology*; D011943:Receptors, Adrenergic, beta / Q000502:physiology*
D002395:Catecholamines; D011942:Receptors, Adrenergic, alpha; D011943:Receptors, Adrenergic, beta; D009647:Normetanephrine; D010643:Phenoxybenzamine; D011433:Propranolol; D009638:Norepinephrine; D004837:Epinephrine; D010646:Phentolamine