Neurobiological orchestration of temporal copulatory patterns of female rat sexual behavior

Abstract

Motivational behaviors are regulated by complex biological mechanisms that integrate an animal’s internal state with external stimuli. Female rat sexual behavior exemplifies this process, as it is an innate and rewarding behavior essential for species survival. While established copulation and motivation research paradigms have provided some insights, these traditional approaches are oversimplified, and the neural mechanisms underlying sexual behaviors are yet to be fully unraveled. This thesis explores the organization and neurobiological orchestration of sexual behavior in female rats in more depth. Paper I provided a framework for a detailed assessment of temporal copulatory patterns, demonstrating that female rat copulation is structured into sexual bouts and time-outs. Low-receptive females exhibited shorter sexual bouts and longer time-outs. In Paper II, we hypothesized that sexual motivation could be divided into two components: sexual incentive motivation (SIM) and motivation to continue copulation (MCC). We successfully developed and validated a test for MCC that used operant conditioning and our bout-based analysis. This study confirmed that SIM and MCC do not correlate and are therefore to be considered two separate components of sexual motivation. These findings provided valuable tools for establishing brain-behavior relationships in sexual behavior research. Hence, in Paper III, we investigated the neural responses of the ventral tegmental area (VTA) in female rat sexual behavior and further tested whether the prolonged exposure to cafeteria (CAF) diet impacts these neural responses and copulation parameters. Our result showed that VTA encodes the start of darts and copulatory stimulations received. Although prolonged CAF diet did not affect copulatory parameters, we observed attenuated VTA neural responses towards a sexual partner in CAF-treated groups. Overall, these findings advance our understanding of female rat sexual behavior by providing novel frameworks for assessing copulation and sexual motivation, emphasizing the need for more extensive behavioral assessments in sexual behavior.