title: The relationships between the cardiovascular effects, alpha- and beta-adrenoceptor blocking actions and plasma concentration of labetalol in doca hypertensive rats.
abstract: The relationships between the cardiovascular effects, alpha- and beta-adrenoceptor blocking actions and plasma concentration of labetalol have been examined in conscious DOCA hypertensive rats. Labetalol (10, 30 and 100 mg/kg p.o.) reduced resting heart rate; blood pressure was reduced only by the two higher doses. The effects lasted 5-24 hours. There was a highly significant correlation between the plasma labetalol concentration and its cardiovascular effects. During the labetalol-induced hypotension and bradycardia the vasopressor responses to intra-arterial injections of phenylephrine were reduced; the tachycardia and vasodepressor responses produced by intra-arterial injections of isoprenaline were also reduced. It is concluded that alpha- and beta-adrenoceptor blockade probably account for the labetalol-induced decreases in resting blood pressure and heart rate respectively.
mesh_terms: D000317:Adrenergic alpha-Antagonists; D000319:Adrenergic beta-Antagonists; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects*; D003864:Depression, Chemical; D003900:Desoxycorticosterone; D004305:Dose-Response Relationship, Drug; D004983:Ethanolamines / Q000494:pharmacology*; D006339:Heart Rate / Q000187:drug effects*; D006973:Hypertension / Q000188:drug therapy; D007545:Isoproterenol / Q000037:antagonists & inhibitors; D007741:Labetalol / Q000494:pharmacology*; D008297:Male; D010656:Phenylephrine / Q000037:antagonists & inhibitors; D051381:Rats
chemical_list: D000317:Adrenergic alpha-Antagonists; D000319:Adrenergic beta-Antagonists; D004983:Ethanolamines; D010656:Phenylephrine; D003900:Desoxycorticosterone; D007545:Isoproterenol; D007741:Labetalol