Interaction between narcotic antagonist (naloxone) and lysergic acid diethylamide (LSD) in the rat.

LSD administration in rats elicited a diphasic reaction consisting of a brief excitable period ( up to 8 min) followed by a prolonged catalepsy (8 min-1 h). While the cataleptic response was antagonized by a single injection of naloxone (given 30 min after LSD administration), pretreatment with naloxone shortened the excitable phase and potentiated the catalepsy.