There is no author summary for this article yet. Authors can add summaries to their articles on ScienceOpen to make them more accessible to a non-specialist audience.
Abstract
The emetic and antiemetic effects of opioid agonists were studied in awake dogs. The
mu-agonists morphine, fentanyl and methadone, in sedative doses, prevented the emetic
response to apomorphine and copper sulphate; only morphine induced emesis, at doses
lower than those required to prevent emesis. The delta-agonist [D-Ala2,Met5]enkephalinamide
(DALA) and [Leu5]enkephalin induced emesis in some of the dogs studied but had no
antiemetic activity. The kappa-agonists bremazocine and ethylketocyclazocine (EKC)
did not induce emesis but, at sedative doses, prevented the emetic response to apomorphine.
The emetic effect of DALA was antagonized by naloxone in some dogs; the antiemetic
effect of morphine, bremazocine and EKC was blocked by both naloxone and MR 2266.
The non-opioid sedatives diazepam, phenobarbital and xylazine, administered in sedative
doses, did not prevent apomorphine-induced emesis. Our results suggest that a delta-receptor
is involved in the emetic effect and a mu- and/or or kappa-receptor in the antiemetic
effect of opioids.