The Effects of Perinatal Androgen Deprivation on Locomotor Activity in Male Rats

Abstract

Testosterone and its metabolites—estrogen and dihydrotestosterone— are involved in the brain sex differentiation during the perinatal period by binding to androgen receptors (AR) or estrogen receptors (ER). However, in the presence of flutamide (FLU), testosterone that is metabolized to estrogen will only bind to ER. Blockade of AR using FLU during the perinatal period could alter the levels of estrogen, which in turn, may modulate the sex differentiation of the brain. This study tested perinatal androgen deprivation on estrogen levels and, in turn, its effects on locomotor activity in male rats.Long‐Evans rats (N=37) were divided into two groups: Group 1 received FLU (20 mg/kg; SC) during perinatal period (prenatal day 4 ‐ postnatal day 4) & Group 2 served as control. On postnatal day 65, these groups were divided into 3 subgroups (injected 5 days/week x 7 weeks): A. finasteride (20 mg/kg, SC), an α‐reductase inhibitor, B. letrozole (2 mg/kg, SC), an aromatase inhibitor and C. vehicle.Open Field (OF) Paradigm: Each animal was tested every week in an OF apparatus where the rat was allowed to explore the OF for 6 minutes. The time spent in the center of the field was compared with the time spent in the periphery using Any‐Maze. In addition, serum estrogen levels were measured using ELISA.Animals receiving FLU not only had high serum estrogen levels but also showed increased locomotor activity by spending significantly more time in the center field. These results suggest that perinatal androgen deprivation results in high levels of estrogen that may contribute to their willingness to explore freely.