ROLE OF STIMULUS LOCALE ON STRAIN DIFFERENCES IN ACTIVE-AVOIDANCE AFTER SCOPOLAMINE OR D-AMPHETAMINE TREATMENT

Three strains of mice were trained in a shuttle avoidance task following treatment with scopolamine (2.0 mg/kg) of d-amphetamine (3.0 mg/kg). When required to run towards light conditioned stimulus to avoid shock, A/J mice acquired the response more readily than DBA/2J or C57BL/6J mice. When required to run away from the light, the strain differences were eliminated. Under both testing conditions scopolamine and d-amphetamine augmented the performance of A/J mice, but had no effect or even disrupted performance of C57BL/6J. In DBA/2J mice d-amphetamine augmented performance only in the approach condition. The hypothesis that scopolamine and d-amphetamine improve performance by response disinhibition and response excitation, respectively is supported. The presence of associative difficulties limits the effects of these agents.