Differences of nu/+ and nu/nu mice in some behaviors reflecting temperament traits

The goal of this paper is to discover a pattern of consistent behavioral differences between athymic CD1 nu/nu mice and euthymic CD1 nu/+ ones. The following behaviors, thought to be correlates of temperament traits, were measured along 3 trials: ambulation, rear, and defecation in two open fields of varying light intensity, interaction time with a conspecific, and variables in the light-darkness test (time in the lit compartment, latency to leave the dark compartment, and number of crossings between compartments). Besides, weight and (IgM and IgG) antibodies to rat erythrocytes were measured. Relative to nu/nu mice, nu/+ mice were heavier, yielded much higher antibody responses, interacted more with a conspecific (the males, but not the females), and ambulated slightly more in the open fields, although the proportion of variance in the behaviors accounted for by the nude mutation was small (< 20%). Therefore, the nude mutation participated in the expression of the activity or extraversion traits.