Changes in brain N-demethylation and opiate receptor content correlate with analgesic effectiveness of morphine.
Castration of male rats results in an increase in the analgesic effectiveness of morphine. This change is abolished by testosterone replacement. The greater effectiveness of morphine in the castrated rats is not due to differences in liver metabolism but correlates with increases in brain N-demethylation and opiate receptor content.
D000728:Androgens / Q000494:pharmacology; D000818:Animals; D001921:Brain / Q000378:metabolism*; D002369:Castration; D003640:Dealkylation; D008297:Male; D009020:Morphine / Q000494:pharmacology*; D010634:Phenobarbital / Q000494:pharmacology; D051381:Rats; D011930:Reaction Time / Q000187:drug effects; D011957:Receptors, Opioid / Q000187:drug effects*
D000728:Androgens; D011957:Receptors, Opioid; D009020:Morphine; D010634:Phenobarbital