[Response types to shock and avoidance learning in inbred strains of mice]

The effects of shock intensity on response types to shock (Experiment 1) and the relationship between response types and avoidance learning (Experiment 2) were investigated in four inbred strains of mice (BALB/c, C3H/He, C57BL/6 and DBA/2J). In Experiment 1, mice received a one-second inescapable shock, which ranged in intensity from .01 to .4 mA (12 levels). Response types to shock were observed, and locomotion increased in all strains as the shock intensity increased. Additionally, the C3H/He strain also increased jumping response at shocks greater than .2 mA. In Experiment 2, the four strains were trained for shuttle avoidance with three shock intensities (.06, .16 and .4 mA). Two responses, locomotion into the adjacent compartment (L-typed) and rearing or jumping (R-typed), were equally effective in terminating the shock. While all strains learned the task at all the levels of shock intensities, the performance of the BALB/c strain declined as the intensity decreased. BALB/c and C57BL/6 strains avoided the shocks mainly by L-typed response across all the intensities. Likewise, the DBA/2J strain predominately displayed L-typed responses, but some R-typed responses did occur. The C3H/He strain, on the other hand, largely avoided the shocks by the R-typed response, especially in the .06 and .4 mA conditions.