The effects of levo-alpha-acetylmethadol and its metabolites on schedule-controlled behavior in the pigeon.

The effects of orally administered levo-alpha-acetylmethadol (LAAM) on the schedule-controlled behavior of the pigeon were compared with those of methadone. Both LAAM and methadone decreased rates of responding under a multiple fixed-interval 5-min, fixed-ratio 30-response schedule of food presentation. Although LAAM had a longer duration of action than methadone, both drugs were similar in the onset and potency of their behavioral effects. The chronic administration of either LAAM or methadone produced tolerance to the respective behavioral effects of each drug. In one set of experiments, the behavioral effects of intramuscularly administered LAAM were compared with those of its active metabolites, levo-alpha-noracetylmethadol and levo-alpha-dinoracetylmethadol. All three drugs decreased rates of responding under both components of the multiple schedule. The onset of these rate-decreasing effects was rapid and the order of potency for the production of these rate-decreases was levo-alpha-noracetylmethadol greater than levo-alpha-dinoracetylmethadol greater than or equal to LAAM. The rate-decreasing effects of LAAM and its metabolites were typical narcotic effects as defined by their reversal by naloxone.