Conditioned lever-press avoidance response in mice: acquisition processes and effects of diazepam

Acquisition of conditioned lever-press avoidance behavior on a continuous avoidance schedule (response-shock interval = 30 s and shock-shock interval = 5 s) and on a discrete avoidance schedule (intertrial interval = 25 s and duration of the warning presentation = 5 s with an escape contingency) in dd mice was investigated. When the behavioral baseline had stabilized, the effects of diazepam on avoidance behaviors were examined. About 60% and 80% of the mice achieved criterion levels of avoidance behavior under continuous avoidance (shock rate being less than 0.5/min) and discrete avoidance (avoidance rate being higher than 75%), respectively. Diazepam (0.5--4 mg/kg SC) dose-dependently impaired avoidance behavior of mice which had a low baseline shock rate and a high baseline avoidance rate under continuous and discrete avoidances, respectively. The changes in avoidance behavior in mice after diazepam were almost identical with those previously found in rats.