Attenuation of the behavioral effects of meperidine and normeperidine by daily administration of diazepam.

The effects of meperidine, normeperidine, morphine, pentobarbital and d-methadone were determined on the key-pecking behavior of pigeons responding under a multiple fixed-ratio (FR), fixed-interval (FI) schedule of grain presentation. Dose-effect curves were obtained for each drug alone and during daily administration of 10 mg/kg of diazepam. The daily administration of diazepam had little effect on the behavior itself. Meperidine and normeperidine caused dose-related decreases in both FI and FR responding. The dose-effect curves for these drugs during daily administration of diazepam were shifted to the right compared to the dose-effect curves determined in the absence of daily diazepam. In contrast, the effects of morphine, d-methadone and pentobarbital either were not affected by daily administration of diazepam or were shifted to the left by daily administration of diazepam. These data further support the hypothesis that the behavioral effects of meperidine and normeperidine are due to a proconvulsive action produced by these drugs. In contrast, the effects of morphine, d-methadone and pentobarbital are not due to such a proconvulsive action.