Reduced locomotor activity in an ovarian-intact rat model of PCOS induced by mild exposure to dihydrotestosterone

Androgen excess is thought to play a crucial role in the onset and progression of polycystic ovary syndrome (PCOS), although the underlying mechanism remains unclear. Using our mild dihydrotestosterone (DHT)-exposed rat model, which more closely reproduces human PCOS phenotypes than conventional models, we examined whether the presence of ovaries is essential in the pathophysiology of PCOS induced by androgen excess. At 26 days of age, female rats were divided into two primary groups: bilaterally ovariectomized (OVX) and sham-operated (intact). Each group was further divided into PCOS (implanted with a tube filled with diluted DHT) and control (implanted with an empty tube) groups. Body weight and food intake were measured weekly. At 58 and 59 days of age, locomotor activity and body temperature were measured. At 87 days of age, brain, blood, and fat tissues were collected and analyzed. Body weight, food intake, adipocyte size, weight of visceral and subcutaneous fat, and serum leptin levels were higher in the intact-PCOS group than the intact-control group, but there were no significant differences between the OVX-PCOS and OVX-control groups. In the intact-PCOS group, compared with the intact-control group, locomotor activity was significantly lower, particularly in the light phase, and body temperature was significantly higher in the darkness phase, whereas there were no significant differences between the OVX-PCOS and OVX-control groups. The effects of androgen might depend on the estrogen milieu, suggesting that the presence of ovaries is essential in the pathophysiologic development and progression of androgen-induced PCOS.