A classical genetic analysis of two apomorphine-induced behaviors in the mouse

Apomorphine (3 mg/kg) produced in C57BL/6 (C57) mice a clear-cut increase in locomotor activity and climbing behavior in comparison with saline, while in DBA/2 (DBA) mice it produced a clear-cut decrease in locomotion and a small reduction in climbing behavior. Genetic analysis involving F1 and F2 hybrids and the backcross populations (F1 x C57; F1 x DBA) indicated that apomorphine-induced locomotion and climbing are inherited through different modes of inheritance. With regard to climbing behavior the mean analysis of apomorphine parameters showed that the additive-dominance model fitted adequately, while this single model did not fit the locomotor activity data for which the best fitting model involved epistatic parameter. Moreover, a zero correlation between the two behaviors in the F2 generation resulted, indicating that no relationship exists between these apomorphine-induced behaviors under our experimental conditions. These results suggest that the horizontal locomotion and climbing are distinct behaviors controlled, at least in part, by different genetic factors related to different dopaminergic mechanisms.