Narcotic abstinence in dependent rats: EEG and behavioral correlates.

The purpose of the study was to assess and compare EEG and behavioral correlates of abstinence from morphine, methadone, LAAM, NLAAM, and DNLAAM in dependent rats. Rats were initially trained to lever press for self-injections on a FR-20 schedule of reinforcement. Following substitution of saline for each of the narcotic agonists. REM sleep was significantly suppressed during morphine, methadone, and NLAAM abstinence, but not during LAAM and DNLAAM abstinence. Significant increases in lever pressing for saline during abstinence from morphine, methadone, and NLAAM emerged earlier than with LAAM and DNLAAM. Significant increases in head-shake behavior occurred during morphine, methadone, NLAAM, and DNLAAM abstinence, but not during LAAM abstinence. These results demonstrated further pharmacodynamic differences between the five narcotics studied. Our findings suggested that in dependent rats abstinence from LAAM was the least severe when compared with abstinence from any of the other four narcotic studied.