Possible Interaction: Morphine and Yohimbine

“Although yohimbine by itself did not affect the pain, the overall analgesic effect of morphine was significantly enhanced in the presence of yohimbine.”

“Moreover, morphine (0.6–5 µM) markedly inhibited prostaglandin E1 (10 µM)-induced cyclic AMP formation in human platelets, while yohimbine (0.1 µM) significantly reversed the inhibition of cyclic AMP by morphine (0.6 and 1 µM) in this study.”

“ Yohimbine (0.1 µM), a specific α2-adrenoceptor antagonist, markedly abolished the potentiation of morphine in platelet aggregation stimulated by agonists.”

“ Yohimbine effectively prevented the effects of the lower concentrations of morphine when added to the incubation medium at 10microM, a concentration devoid of significant toxicity.”

“Moreover, morphine (0.6–5 &mgr;M) markedly inhibited prostaglandin E1 (10 &mgr;M)-induced cAMP formation in human platelets, and yohimbine (0.1 &mgr;M) significantly reversed the inhibition of cAMP by morphine (0.6 and 1 &mgr;M) in this study.”

“Morphine (1 and 5 &mgr;M) significantly potentiated thromboxane B2 formation stimulated by collagen in human platelets, and yohimbine also reversed this effect of morphine in this study.”

“ Yohimbine (0.1 &mgr;M), a specific &agr;2-adrenoceptor antagonist, markedly abolished the potentiation of morphine in platelet aggregation stimulated by collagen.”

“Furthermore, post-training intra-mPFC microinjection of ineffective doses of yohimbine or clonidine significantly reversed the inhibitory effect of morphine on memory retrieval.”

“The membrane expression of α(2A)-adrenoceptors in the pons/medulla was decreased in morphine withdrawn animals; this reduction was prevented by repeated administration of YKS or yohimbine.”

“ Yohimbine (α2-adrenergic receptor antagonist) blocked the clonidine-induced potentiation of analgesic effect of morphine (p = 0.036) and oxycodone (p = 0.0167), while yohimbine did not affect BMS182874-induced potentiation of the analgesic effect of morphine or oxycodone.”

“Chronic administration of yohimbine alone also increased midkine expression levels, whereas yohimbine and morphine administered together exhibited summatory effects on the upregulation of midkine expression levels.”

“All effects of morphine were antagonized by naloxone, as well as theα-receptor antagonist, yohimbine.”

“The present study demonstrates that yohimbine pretreatment reduces long-term morphine exposure-induced alterations in the astroglial reaction, suggesting that alpha(2)-adrenergic mechanisms may play an important role in mediating morphine-induced pathological effects in the brain.”