Effects of combined treatment with nortriptiline and lorazepam on conflict behavior and motility of rats.

Lorazepam attenuated the suppressant effects of punishment on the response rate of rats in the multiple schedule of reinforcement devised by Geller and Seifter (1960). Nortriptiline alone was ineffective on punished responses. Both drugs, at certain dose levels, inhibited the nonpunished response. Combined treatment with the two drugs in a dose ratio of 1:20 attenuated the effects of punishment at all dose levels tested. The effects of the combination upon both punished and nonpunished responding was greater than might be accounted for by a simple additive effect of the individual treatments. Lorazepam and nortriptiline both induced a dose-related decrease in the locomotor activity of rats; when given together the 2 drugs antagonized each other. The results give an experimental support to the clinical observations about the usefulness of the benzodiazepine-antidepressant combination in certain depressive illnesses.