title: Effects of beta-adrenergic receptor blocking agents on blood pressure in conscious hypertensive rats.
abstract: The effects of beta-adrenergic receptor blocking agents administered i.v. on the blood pressure in conscious spontaneously hypertensive rats (SHR), renal hypertensive rats (RHR) and normotensive Wistar strain rats (NR) were studied. dl-Propranolol and dl-YB-2, 1 mg/kg i.v., caused a sustained rise in blood pressure in SHR and RHR. The maximum response of each beta-blocking agent after phentolamine, 10 mg/kg i.v., in SHR and RHR was significantly larger than that in NR. The potency ratio for the hypertensive activities of the 1- and d-isomers of propranolol and YB-2 was similar to the ratio of their beta-blocking activities. The pressor effects of the beta-blocking agents after phentolamine were significantly inhibited by adrenalectomy, reserpinization and pretreatment with hexamethonium. The results suggest that the pressor effect of the beta-blocking agents may be due to their beta-blocking activities and the unmasking of alpha-receptor activities of the blood vessels. Furthermore, the greater pressor effect of the agents observed in hypertensive rats is attributed to a greater activity of the sympathetic nervous system in these rats as compared to normotensive rats.
mesh_terms: D000315:Adrenalectomy; D000319:Adrenergic beta-Antagonists / Q000494:pharmacology*; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D006339:Heart Rate / Q000187:drug effects; D006584:Hexamethonium Compounds / Q000494:pharmacology; D006973:Hypertension / Q000503:physiopathology*; D006977:Hypertension, Renal / Q000503:physiopathology; D007192:Indenes / Q000494:pharmacology; D008297:Male; D010646:Phentolamine / Q000494:pharmacology; D011217:Practolol / Q000494:pharmacology; D011412:Propanolamines / Q000494:pharmacology; D051381:Rats; D012110:Reserpine / Q000494:pharmacology; D013237:Stereoisomerism; D014439:Tyramine / Q000494:pharmacology
chemical_list: D000319:Adrenergic beta-Antagonists; D006584:Hexamethonium Compounds; D007192:Indenes; D011412:Propanolamines; D012110:Reserpine; D011217:Practolol; D014439:Tyramine; D010646:Phentolamine