Behavioral dynamics of different stages of sexual motivation in male and female rats

Abstract

Sexual motivation is a complex concept involving both the initial drive to begin mating and the motivation to sustain copulation. Disruptions in sexual motivation are often observed in psychiatric disorders. This study proposes that sexual motivation can be divided into two distinct components: sexual incentive motivation and the drive to sustain copulation. To investigate this, we utilized the Motivation to Continue Copulation (MCC) test, which measures effort (nose pokes) to gain access to a sexual reward, and compared it with the Sexual Incentive Motivation (SIM) test and standard copulation tests. Male and female rats were trained on a fixed ratio (FR) 1 schedule using cheese rewards before transitioning to sexual rewards. After six FR1 sessions, the effort required increased to FR5 and progressive ratio (PR) schedules. Results revealed that sexual incentive motivation, measured by the SIM test, was higher in males after sexual experience, while females maintained consistent levels. In the MCC test, both males and females exhibited increased motivation to continue copulation with experience, but the motivation declined in the 2nd ejaculatory series. These findings demonstrate that sexual motivation comprises distinct components. The MCC test effectively measures the drive to sustain copulation, while the SIM test assesses incentive motivation. This distinction is crucial for advancing behavioral neuroscience and understanding sexual dysfunction in psychiatric conditions.