The facilitating effects of acute oxytocin treatment on pacing and proceptive sexual behaviours are dose-dependent

Conall E. Mac Cionnaith, Eamonn L. Gomez-Perales, Wayne G. Brake and James G. Pfaus

Presented at Society for Neuroscience 2019 Chicago

Accepted abstract

Several studies have reported that oxytocin (OT) administration increases lordosis quotients in female rats. However, the lordosis reflex is only one of many behaviours that are important during mating in the female rat. Proceptive behaviours (i.e. solicitations and hops and darts) and pacing are important for successful impregnation. Therefore, the current study tests the effects of different doses of oxytocin on a variety of sexual behavioural measures. Thirty female Long-Evans (LE) rats were randomised to be intraperitoneally injected with 20µg OT, 50µg OT, or saline one minute prior to copulation (n = 10 per group). Females copulated with an LE male in unilevel Plexiglass pacing chambers for 30 minutes. Trials were recorded and scored for: female entries to the male compartment, the latency to return to the male after leaving the male’s compartment, solicitations, hops and darts, intromissions and ejaculations received, and the amount of time spent with a male. All behaviours were analysed with one-way ANOVAs, followed by Holm-adjusted group comparisons. Females treated with 50µg OT took longer to return to the male chamber and made fewer entries to the male’s compartment compared to the 20µg OT group. They also received fewer intromissions and ejaculations. Additionally, females treated with 50µg OT made fewer hops and darts and fewer solicitations than females given 20µg OT. Conversely, 20µg OT females made more proceptive behaviours and entries to the male compartment compared to 50µg OT females. There was also a trend for females given 20µg OT to make more solicitations and hops and darts than saline treated females. Thus, OT may acutely facilitate female sexual behaviour, but these effects are dose dependent; 20µg OT facilitates sexual behaviours whereas 50µg OT is inhibitory.