title: Baroreflex sensitivity alteration following transient hemispheric ischaemia in rats: protective effect of alphamethyldopa and guanfacine.
abstract: The reflex tachycardia to arterial vasodilation was analysed in anaesthetized and ventilated Long Evans rats. Nicardipine was given by slow intravenous injection. The decrease in blood pressure was accompanied by a sympathetically mediated reflex tachycardia. The slope of the mean blood pressure-pulse period relationship was considered as an index of baroreflex sensitivity. Two injections of nicardipine were given during a single experiment. For studying the suprapontine control of the baroreflex arc, rats were subjected to transient (10 min) bilateral hemispheric ischaemia. These rats exhibited a blood pressure drop following recirculation and baroreflex sensitivity was impaired. Pretreatment with alpha-methyldopa, guanfacine and enalapril lowered mean blood pressure to a similar extent. In those rats pretreated with alpha-methyldopa and guanfacine transient hemispheric ischaemia did not alter baroreflex sensitivity while enalapril pretreated rats exhibited an impaired baroreflex. The protective effect of alpha-methyldopa and guanfacine against the cardiovascular consequence of hemispheric ischaemia may depend on reduced monoamine turnover resulting from central alpha-adrenoceptor stimulation.
mesh_terms: D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D004656:Enalapril / Q000008:administration & dosage; D016316:Guanfacine; D006146:Guanidines / Q000494:pharmacology*; D006339:Heart Rate; D002546:Ischemic Attack, Transient / Q000503:physiopathology*; D007741:Labetalol / Q000008:administration & dosage; D008297:Male; D008750:Methyldopa / Q000494:pharmacology*; D009529:Nicardipine / Q000008:administration & dosage; D010648:Phenylacetates / Q000494:pharmacology*; D011311:Pressoreceptors / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D011919:Rats, Inbred Strains; D012018:Reflex; D013610:Tachycardia / Q000139:chemically induced / Q000503:physiopathology
chemical_list: D006146:Guanidines; D010648:Phenylacetates; D016316:Guanfacine; D008750:Methyldopa; D004656:Enalapril; D009529:Nicardipine; D007741:Labetalol