Differential testosterone secretory capacity of the testes of aggressive and nonaggressive house mice during ontogeny

In this study, testosterone secretory capacity of testicular Leydig cells during ontogeny was determined in males of an aggressive and a nonaggressive genetic selection line of wild house mice. Neonates, 23-day-old prepubertals, and adult male mice were studied. A morphometric method was used to quantify 3-beta-hydroxy steroid dehydrogenase (3-beta-HSD)-stained Leydig cells in testicular sections to determine testosterone secretory capacity. We consider this parameter to reflect circulating testosterone in the plasma. The results of this study show that the testosterone secretory capacity of Leydig cells in the testis changes differentially during development in males of the aggressive and nonaggressive selection lines. This capacity is highest in the aggressive selection line males at adulthood and at the prepubertal age of 23 days. Surprisingly, at birth, the highest T-secretory capacity was observed in the males of the nonaggressive selection line. The significance of an interaction between genetic factors and differences in perinatal testosterone for the individual variation in adult aggressive behavior is discussed.