title: Platelet alpha 2-adrenoceptors in heroin addicts during withdrawal and after treatment with clonidine.
abstract: The density of platelet alpha 2-adrenoceptors, quantitated by means of the binding of [3H]clonidine and [3H]yohimbine, and the aggregation response induced by adrenaline were investigated in thirty-two heroin addicts during spontaneous withdrawal. The number of binding sites for [3H]clonidine, but not for [3H]yohimbine, was significantly increased during withdrawal and the increase followed a time course related to the severity of the abstinence syndrome. There was a positive and significant correlation between the severity of withdrawal and the density of platelet alpha 2-adrenoceptors. Concomitantly, the adrenaline-induced platelet aggregation was potentiated. Treatment with clonidine led to significant decreases in receptor densities as well as in functional responses. These results suggest that only alpha 2-adrenoceptors in the agonist state (i.e. number of binding sites for [3H]clonidine) are modulated during the development of the heroin withdrawal syndrome.
mesh_terms: D000328:Adult; D001792:Blood Platelets / Q000187:drug effects / Q000378:metabolism*; D003000:Clonidine / Q000097:blood / Q000494:pharmacology; D004837:Epinephrine / Q000494:pharmacology; D005260:Female; D006556:Heroin Dependence / Q000097:blood*; D006801:Humans; D066298:In Vitro Techniques; D007700:Kinetics; D008297:Male; D010974:Platelet Aggregation / Q000187:drug effects; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects / Q000378:metabolism*; D013375:Substance Withdrawal Syndrome / Q000097:blood* / Q000188:drug therapy
chemical_list: D011942:Receptors, Adrenergic, alpha; D003000:Clonidine; D004837:Epinephrine