| Abstract: | The effects of various agonists and antagonists of both alpha and beta adrenoceptors on the acquisition of avoidance behaviour were investigated in the rat. Clonidine, a selective agonist of alpha 2 adrenoceptors depressed avoidance acquisition whilst yohimbine, an antagonist of these receptors produced an opposite effect. Prazosin which showed postsynaptic alpha 1 adrenoceptor blocking activity reduced avoidance behaviour. A similar effect was produced by propranolol, a non-selective antagonist of beta adrenoceptors. On the other hand, salbutamol preferentially stimulating beta 2 adrenoceptors facilitated avoidance behaviour. In general, the results show a fairly good correlation between avoidance acquisition and efficacy of noradrenergic neurotransmission. |
