Intrathecal pentobarbital prevents naloxone-induced facilitation of the tail-flick response in the rat.
In rats with acute transection of the lower thoracic spinal cord, intrathecal administration of naloxone in doses of 1, 2, 5 and 50 microgram dose-dependently reduced the latency of the tail-flick response to radiant heat. An intrathecal injection of pentobarbital (100 microgram) prolonged the latency and prevented the facilitatory effect of naloxone. It is concluded that the antagonism between naloxone and pentobarbital is of the non-competitive or functional (physiological) type.
D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D005260:Female; D009270:Naloxone / Q000494:pharmacology*; D010146:Pain / Q000503:physiopathology*; D010634:Phenobarbital / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D013116:Spinal Cord / Q000502:physiology
D009270:Naloxone; D010634:Phenobarbital