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.
Key words LSD 
bad trip
- Rats - Cataleptic analgesia - Narcotic antagonist - Naloxone-LSD antagonism