The effect of diazepam, chlorpromazine and amobarbital on the contingent negative variation.

The effects of diazepam (5 mg), chlorpromazine (CPZ, 12.5 mg) and amobarbital (100 mg) on the contingent negative variation (CNV) at Cz and Oz were studied in groups of 10 subjects each. Amobarbital and placebo were given by the double-blind crossover method. Two kinds of experimental paradigms were used: Click (warning stimulus, S1)--flashes (imperative stimulus, S2)--and click--electrical stimulation--motor response. The results obtained were as follows; 1) CNV amplitudes were decreased significantly by administration of diazepam only at Cz when S2 was flashes and at both Cz and Oz when S2 was electrical stimulation. 2) CPZ-induced effects were of either augmentation or decrement in CNV amplitudes depending on the subject and on the modality of S2. Involvement of dose-dependent factor was suggested. 3) Amobarbital and placebo did not give any significant changes to the CNV. 4) Significant correlations between CNV amplitudes at Cz and Oz were found before drug administration and even after taking drugs exclusive of diazepam. Its decremental ratio from Cz to Oz was approximately 0.6 to 0.8. The correlation coefficient became to be insignificant after taking diazepam only when S2 was flashes.