Clonidine and a beta-agonists induce hyperthermia in rats at high ambient temperature.
The effects of the alpha-agonist clonidine and the beta-agonist clenbuterol on body temperature of rats kept at high ambient temperature (28 degrees C) were studied. Both drugs induced a dose-dependent significant increase in temperature. The clonidine-induced hyperthermia was blocked by various alpha 2-antagonists, yohimbine, rauwolscine and RX 781094 and the alpha 1-antagonists, prazosin and corynanthine but not by 1-propranolol, spiperone, metergoline. The hyperthermic effect of clonidine was potentiated in rats after a lesion of the central noradrenergic terminals by DSP-4. The clenbuterol-induced hyperthermia was counteracted by 1-propranolol, yohimbine and rauwolscine but not by atenolol, prazosin, spiperone, metergoline. These observations indicate that clonidine- and clenbuterol-induced hyperthermia is mediated by alpha 2-(postsynaptic) and beta-adrenoceptors, respectively. Moreover, in the latter effect alpha 2-adrenoceptors are involved. The simple temperature measurement can thus be used as a preliminary indicator of central alpha 2- or beta-agonistic properties of the screened drug.
D000818:Animals; D001831:Body Temperature / Q000187:drug effects*; D001921:Brain / Q000187:drug effects*; D002976:Clenbuterol / Q000494:pharmacology*; D003000:Clonidine / Q000494:pharmacology*; D004777:Environment; D004983:Ethanolamines / Q000494:pharmacology*; D006979:Hyperthermia, Induced; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects*; D011943:Receptors, Adrenergic, beta / Q000187:drug effects*; D013696:Temperature
D004983:Ethanolamines; D011942:Receptors, Adrenergic, alpha; D011943:Receptors, Adrenergic, beta; D003000:Clonidine; D002976:Clenbuterol