Meperidine's effect under shock titration and shock discrimination procedures.

Meperidine's effects were examined under a schedule of shock titration and under a shock intensity discrimination in which squirrel monkeys discriminated between the presence and absence of a low intensity shock. Meperidine did not increase the intensity at which monkeys maintained the shock in the shock titration procedure, nor did meperidine alter the percentage of correct responses under the shock intensity discrimination although meperidine did increase the time to respond in the presence and absence of shock. When meperidine was combined with a dose of SKF-525A, which did not alter responding when given alone, the intensity at which monkeys maintained the shock under the shock titration procedure was increased. Moreover, the percentage of correct responses in the presence of shock under the shock titration procedure was decreased by the combination of meperidine and SKF-525A.