Central and peripheral effects of oxytocin administration in prairie voles ( Microtus ochrogaster)

Abstract

The present study examined the hypothesis that oxytocin (OT) may influence female sexual behavior in prairie voles ( Microtus ochrogaster). The effectiveness of OT to induce sexual behavior was tested in ovariectomized females that were injected daily with estradiol benzoate (EB, 0.02 μg, twice), a dose insufficient for estrus induction. On the third day females received intracerebroventricular (ICV) injections of OT (1, 300, or 1000 ng) or saline vehicle. In the presence of minimal estrogen stimulation, OT did not induce sexual receptivity, or influence autogrooming or other social interactions. The behavioral effects of OT were examined in another group of ovariectomized females that received daily oil or EB injections (10 μg, twice) followed on the third day by either ICV (1, 300, or 1000 ng) or intraperitoneal (IP) (1, 3, or 10 μg) injections of OT. Among EB-treated females, only those in confirmed estrus, prior to ICV or IP injection, were included in these studies. There was a dose-related decrease in the percentage of females that remained in behavioral estrus after ICV OT. In those females that continued to show sexual behavior, lordosis frequencies and durations were unaffected by ICV OT. Nonsexual behavior did not differ between mated females and those exhibiting OT-inhibited sexual behavior. In females that were EB-treated, autogrooming and side-by-side behavior increased after ICV OT, while there was a decline in aggression. Female sexual and nonsexual behaviors were not significantly affected by IP OT. However, males paired with IP-OT females showed reductions in anogenital investigation and aggression toward IP-OT injected females; male autogrooming increased if females were EB-treated and received IP OT. OT did not induce sexual behavior or affect other social behaviors or autogrooming in oil-treated female prairie voles. These results suggest that centrally active OT may inhibit sexual receptivity and promote social behavior and autogrooming in female prairie voles, while peripheral OT may alter the stimulus properties of the female.