Effects of acute morphine pretreatment on the rate-decreasing and antagonist activity of naloxone.

摘要: Rats responded under a schedule in which every 30th lever press (fixed ratio 30) produced food pellet during sessions divided into six 5-min components separated by 10-min timeout (TO) periods. Cumulative doses of morphine or naloxone were administered at the start consecutive TO When given alone, decreased response rates dose-dependent manner, abolishing responding 10 17.8 mg/kg. Naloxone 0.1 and 1.0 mg/kg restored patterns behavior suppressed dose morphine; 0.32 to prevented rate-decreasing effects cumulative doses. initially 32 100 mg/kg; with repeated testing intervening exposure, required was An acute pretreatment, 4 h before session, suppress an additional 10- 30-fold. This effect time-dependent dose-dependent, usual dose-response function could be recaptured 1 week after pretreatment obtained. In contrast, did not alter either itself reverse prevent morphine's effects.