ANDROGEN EXPOSURE AND REPRODUCTIVE-BEHAVIOR OF AN INDUCED OVULATOR, THE PINE VOLE (MICROTUS-PINETORUM)

The actions of steroid hormones on brain and behavior are classically divided into organizational effects that are permanent and occur early in development and activational effects that are temporary and occur throughout life. Here, we test the hypothesis that in an induced ovula tor, testosterone defeminizes only those neural tissues that rely on s ynergistic interactions of estrogen and progesterone for normal functi on in adulthood. Female voles, Microtus pinetorum, injected with testo sterone (T) or oil neonatally were paired with males for an 8-week per iod. During the pairing, androgenized and oil-treated females spent a similar amount of time investigating the caudal and rostral regions of the males. Males spent significantly less time investigating the caud al and rostral regions of androgenized females. Androgenized females m ounted males, did not exhibit lordosis, and were less likely to be mou nted by males. Moreover, none of the 10 androgenized females gave birt h, whereas 8 of 9 control females gave birth. Androgenized females wer e also not capable of being stimulated into reproductive condition by males. Injection of 0.5 mu g of estradiol benzoate for 4 consecutive d ays resulted in reduced uterine hypertrophy in androgenized females. T hese results support the original organizational-activational hypothes is by showing that neonatal androgenization defeminizes and masculiniz es female pine voles. (C) 1996 Academic Press.