Possible Interaction: Adrenergic Alpha-Agonists and Yohimbine

“Recently, the nature of these receptors has come into … insofar as the presynaptic inhibitory effects of the alpha 2-adrenoceptor agonist , clonidine, in the guinea-pig trachea have been shown to be antagonized by the alpha 2-adrenoceptor antagonist, yohimbine , as well as the alpha 1-adrenoceptor antagonist, prazosin.”

“Midaglizole, yohimbine and idazoxan inhibited the pressor responses to B-HT 920 ( alpha 2-adrenoceptor agonist ), in a dose-related manner, to a greater extent than the response to methoxamine (alpha 1-adrenoceptor agonist).”

“ Yohimbine infused at a rate of 20 micrograms kg-1 min-1 suppressed clonidine-induced hyperglycaemia and blocked the inhibitory effect on insulin secretion mediated by the alpha 2-adrenoceptor agonist.”

“In addition, the down-regulation of cytosol estrogen receptors by either the alpha 1-noradrenergic antagonist, prazosin, or the alpha 2-noradrenergic antagonist, yohimbine , could be blocked by pretreatment with the alpha 2-noradrenergic agonist , clonidine.”

“When these cells are incubated with alpha 2-adrenergic agonists , there is a concentration-dependent increase of cyclic GMP that is blocked by the alpha 2-adrenergic antagonist yohimbine but not by the beta-antagonist propranolol.”

“Adrenaline (10(-7) M), with a potent alpha-agonistic action decreased both NA and DA release, and these effects were blocked by pretreatment with yohimbine (10(-7 M).”