Leakage of catecholamines from rabbit cerebrospinal fluid following intracerebroventricular injection.
The intracerebroventricular (i.c.v.) injection of (-)-isoprenaline and the selective beta 1-adrenoceptor agonist, RO363, elicited reproducible dose-related increases in heart rate in unanaesthetized and anaesthetized rabbits. (-)-Isoprenaline produced vasodepressor effects in unanaesthetized animals, whereas both catecholamines decreased blood pressure in anaesthetized rabbits. Pretreatment with guanethidine sulphate (5 mg/kg i.v.) reduced but did not abolish the tachycardia elicited by i.c.v. RO363, whereas heart rate responses to i.c.v. (-)-isoprenaline were unaffected. Pretreatment of anaesthetized rabbits with hexamethonium bromide (10 mg/kg i.v.) did not markedly affect the tachycardia elicited by i.c.v. RO363 and reduced the response to i.c.v. (-)-isoprenaline in only one out of five experiments. The results suggest that there is a marked leakage of centrally administered catecholamines into the peripheral circulation and that the rabbit may be unsuited for examining centrally mediated cardiovascular effects of catecholamines.
D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000818:Animals; D002395:Catecholamines / Q000134:cerebrospinal fluid*; D002396:Catechols; D006145:Guanethidine / Q000494:pharmacology; D018738:Hexamethonium; D006584:Hexamethonium Compounds / Q000494:pharmacology; D007276:Injections, Intraventricular; D007545:Isoproterenol / Q000008:administration & dosage / Q000494:pharmacology; D011412:Propanolamines / Q000008:administration & dosage / Q000494:pharmacology; D011817:Rabbits
D000318:Adrenergic beta-Agonists; D002395:Catecholamines; D002396:Catechols; D006584:Hexamethonium Compounds; D011412:Propanolamines; D018738:Hexamethonium; C018420:Ro 363; D007545:Isoproterenol; D006145:Guanethidine