Differential effects of scopolamine and D-amphetamine on avoidance: Strain interactions.

In a discriminated Y-maze avoidance task it was observed that mice of the A/J strain were superior to mice of the DBA/2J strain, which in turn made more avoidance responses than C57BL/6J mice. Moreover, the A strain was also observed to acquire a discrimination problem more readily than either of the other strains. Administration of scopolamine enhanced active avoidance performance in A, but not DBA/2 or C57BL/6 mice. D-Amphetamine improved performance in both A and DBA/2 mice but had negligible effects on the performance of the C57BL/6 strain. Neither drug affected discrimination performance irrespective of strain. In an inhibitory avoidance task the C57BL/6 strain was found to perform more poorly than the A strain which was inferior to DBA/2 mice. Scopolamine disrupted performance in all three strains, while d-amphetamine was found to disrupt the performance of the A and DBA/2 strains only. The results were interpreted in terms of the role of associative and nonassociative effects of shock in modulating avoidance behavior.