title: Spontaneously hypertensive rats exhibit an enhanced mydriatic response to clonidine. Evidence for enhanced sensitivity of central alpha 2-adrenoceptors.
abstract: Comparisons among spontaneously hypertensive (SHR), Kyoto Wistar (KW), and Wistar (W) rats were made of the functional states of central nervous system (CNS) alpha 2-adrenoceptors (clonidine-induced mydriasis) and nonvascular peripheral presynaptic alpha 2-adrenoceptors (clonidine-induced inhibition of the neurogenic twitch of the isolated vas deferens). While there were no differences among the strains of rats in the concentration of clonidine required to produce a 50% inhibition of the electrically evoked contractile response of the vas deferens, there was a significant reduction in the mean effective concentration (ED50) of clonidine to induce mydriasis in SHR as compared with KW and W rats. These observations indicate that CNS alpha 2-adrenoceptors may be functionally more sensitive in SHR. The data also suggest that the sensitivity of nonvascular presynaptic alpha 2-adrenoceptors, at least in the vas deferens, is not altered in hypertensive animals.
mesh_terms: D000818:Animals; D001921:Brain / Q000187:drug effects*; D003000:Clonidine / Q000494:pharmacology*; D006973:Hypertension / Q000503:physiopathology*; D008297:Male; D011680:Pupil / Q000187:drug effects*; D051381:Rats; D011919:Rats, Inbred Strains; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects*
chemical_list: D011942:Receptors, Adrenergic, alpha; D003000:Clonidine