Effects of some psychotropic drugs on M-wave and operant behavior in the squirrel monkey

The effects of low doses of nabilone, chlorpromazine, pentobarbital, meprobamate, diazepam, chlordiazepoxiOde and d-amphetamine on behavioral responding to cues signalling the availability of food rewards, and on the M-wave, an evoked cortical potential previously reported to reflect the conditioned incentive value of the cues were determined in the squirrel monkey. Nabilone and chlorpromazine simultaneously depressed both the M-wave and behavior. Pentobarbital, meprobamate, diazepam and chlordiazepoxide could depress the M-wave without depressing behavior. This effect was most marked with diazepam. The only augmentation of the M-wave observed was the d-amphetamine, and this occurred in only one of five animals. The benzodiazepines were the only drugs to augment behavioral output. However, diazepam occasionally increased the number of cures responded to while concomitantly decreasing both total behavioral output and the amplitude of the M-wave. It is concluded that the M-wave cannot directly reflect the incentive value of the cue, but must rather reflect something that tends to parallel this value.