EXPOSURE TO MALE SIBLINGS FACILITATES THE RESPONSE TO ESTRADIOL IN SEXUALLY NAIVE FEMALE PRAIRIE VOLES

Female prairie voles undergo induced estrus, and require both physical contact with males and exposure to male urine to become reproductivel y active. This study attempted to determine if physical contact with m ales enhanced female response to estradiol. Two groups of sexually nai ve females were tested. One was reared without any exposure to males a fter weaning, and the other was reared with sibling males to 60 days o f age. Sibling males were used because females avoid direct contact wi th the urine of related males, allowing for the establishment of a gro up of females that experienced physical contact in the relative absenc e of exposure to male pheromones associated with urine. Females were t hen subcutaneously injected with 0.5 mu g estradiol benzoate once a da y for 7 days. Sexual receptivity was tested with novel adult males 48 h and 168 h after the first injection. There was a significant differe nce between the treatment groups, with 10% of sexually naive females r eared without sibling males displaying lordosis compared to 70% of fem ales raised with sibling males. The results indicate that exposure to sibling males significantly increased a female's behavioral response t o estradiol. (C) 1997 Elsevier Science Inc.