The role of postnatal testosterone in the development of sexually dimorphic behaviors in DBA/1Bg mice.

The DBA/1 Y chromosome causes an increment in aggression and pubertal testosterone levels. The purpose of the following experiments was to determine whether pubertal testosterone is necessary for the normal development of both aggression and copulation in males. If it is, then the effect of the DBA/1 Y chromosome may be mediated by its influence on pubertal testosterone. Individuals were either castrated at 30 days of age (CAS30) or sham operated (Sham or CAS50). At 50 days of age, the CAS30 individuals were sham operated and replaced with testosterone, while the CAS50 group was castrated and replaced with the same quantity of testosterone. The shams were sham operated at 50 days of age. CAS30 individuals were less aggressive than the CAS50 group, while they were no less aggressive than the sham operated group. Additionally, no groups differed in male copulatory behaviors. The results are discussed in relation to Y chromosomal and developmental mechanisms of sexually dimorphic behaviors.