BACLOFEN SUPPRESSION OF COCAINE SELF-ADMINISTRATION - DEMONSTRATION USING A DISCRETE TRIALS PROCEDURE

We have previously reported that rats display a circadian pattern of c ocaine self-administration if access to drug is limited to 10-min disc rete trials that are separated by at least 20 min. In the present stud y, the pattern of cocaine intake (1.5 mg/kg per injection) was studied in two large groups of animals that were maintained on different 12-h light/dark cycles (3 a.m. to 3 p.m. versus 10 a.m. to 10 p.m.). Regar dless of the time of light onset, a circadian pattern of cocaine self- administration was observed. Maximum cocaine intake occurred during th e final 6 h of the dark period and was followed by a relative abstinen ce period during the light phase. This highly predictable pattern of d rug taking behavior provided an opportunity to explore the effect of b aclofen, a GABAB agonist, on the initiation of self-administration beh avior In two separate studies, acute treatment with baclofen (1.25-5.0 mg/kg) was shown to suppress cocaine intake for at least 4 h. Baclofe n had no significant effect on responding for food reinforcement. Prev ious results have indicated that baclofen appears to reduce specifical ly the motivation to respond for cocaine. Together, these data suggest that baclofen should be considered as a possible pharmacotherapeutic agent in cocaine addiction.