title: Adaptive and differential changes on beta- and alpha 2-adrenoreceptors mediated hyperthermia after chronic treatment with antidepressant drugs in the rat kept at high ambient temperature.
abstract: We found previously that the beta-agonist clenbuterol and the alpha-agonist clonidine produced hyperthermia in rats kept at high ambient temperature, which effects were mediated by beta- and alpha 2-adrenoceptors, respectively. In the present paper this observation was used for testing the responsiveness of beta- or alpha 2-adrenoceptors, changed by a pharmacological manipulation, i.e., by chronic treatment with antidepressants. The animals were pretreated with desipramine, imipramine or amitriptyline twice a day for 1 or 2 weeks. All antidepressants significantly attenuated the clenbuterol-induced hyperthermia after 2 weeks of treatment. The effect of desipramine was stronger than that of the other antidepressants and appeared as little as 1 week after the treatment. The hyperthermic effect of clonidine was significantly reduced by repeated treatment with desipramine, increased after 2 weeks administration of imipramine, whereas amitriptyline produced no significant changes. In conclusion, these data suggest that, after repeated treatment, the antidepressants tested produce an adaptive decrease in function of beta-adrenoceptors while the same drugs exert differential effects on alpha 2-receptors. Moreover, clenbuterol induced hyperthermia may be a useful test for examining possible functional changes in beta-adrenoceptor sensitivity.
mesh_terms: D000639:Amitriptyline / Q000494:pharmacology; D000818:Animals; D001831:Body Temperature / Q000187:drug effects*; D001921:Brain / Q000187:drug effects*; D003891:Desipramine / Q000494:pharmacology; D004777:Environment; D006358:Hot Temperature; D006979:Hyperthermia, Induced; D007099:Imipramine / Q000494:pharmacology; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects*; D011943:Receptors, Adrenergic, beta / Q000187:drug effects*
chemical_list: D011942:Receptors, Adrenergic, alpha; D011943:Receptors, Adrenergic, beta; D000639:Amitriptyline; D007099:Imipramine; D003891:Desipramine