Actions of kappa, sigma and partial mu narcotic receptor agonists on rat brain acetylcholine turnover.
Cholinergic neurons which possess mu and delta receptors and/or which are regulated by neurons possessing these receptors, do not appear to have kappa receptors. Only at doses far exceeding (16--32 x) the analgesic ED50 of the prototype kappa antagonist ethylketazocine is acetylcholine turnover depressed in the cortex and hippocampus. This suggests that such activity may involve occupation of mu and/or delta receptors at high doses. The lack of activity of the sigma agonist SKF 10047 also indicates a possible absence of sigma receptors on cholinergic neurons. The partial mu antagonist buprenorphine was found to be a unique narcotic agent in that it behaved as a classical mu agonist at low doses, but as an antagonist at high doses.
D000109:Acetylcholine / Q000378:metabolism*; D000818:Animals; D001921:Brain / Q000187:drug effects / Q000378:metabolism*; D002047:Buprenorphine / Q000494:pharmacology*; D008297:Male; D009019:Morphinans / Q000494:pharmacology*; D009270:Naloxone / Q000494:pharmacology*; D009928:Organ Specificity; D010620:Phenazocine / Q000031:analogs & derivatives* / Q000494:pharmacology; D051381:Rats; D011957:Receptors, Opioid / Q000187:drug effects / Q000502:physiology*
D009019:Morphinans; D011957:Receptors, Opioid; D009270:Naloxone; D002047:Buprenorphine; C012134:SK&F 10047; D010620:Phenazocine; D000109:Acetylcholine