The effects of centrally acting adrenergic agonists on temperature and on explorative and motor behaviour. Relation...

Seven structurally unrelated adrenergic agonists were compared in three models to measure sedation viz. hole-board exploration, open-field activity and rotarod performance. It appeared that all compounds exerted the same order of potency in these models except for BHT-920 which was more active in the open-field. The other compounds were clonidine, azepexole, guanfacine, lofexidine, UK-14.304 and ST-587. The sedative effect appeared to be not causally related with the hypothermic activity since much higher doses were necessary for the latter effect. There was a relation between the sedative effects and the suppression of body shakes and enhanced locomotor activity induced by dipropylacetate, a potent model for morphine-withdrawal behaviour. The body shakes appeared to be more sensitive than locomotor activity suggesting that the antiwithdrawal action of alpha 2-agonists might be intrinsically higher than their sedative action. The data support earlier findings indicating that the antiwithdrawal action of clonidine is mediated by alpha 2-adrenoceptors.