Abstract

Mating strategies describe a set of social and sexual behaviors that an individual, or a species uses in order to reproduce. The two ends of the spectrum of mating strategies are promiscuity, where an individual mates with a variety of partners, and monogamy, where individuals form enduring bonds and preferentially copulate with one another. However, much evidence exists, demonstrating that there is a great deal of flexibility within each of these mating strategies. The three chapters of this thesis were designed to understand how far the mating strategy of the female rat could be shifted, from promiscuity to monogamy, by assessing whether or not female rats would display mate guarding behavior. Chapter 1 showed that sexually naïve female rats, if given all of their rewarding sexual experience with the same male, would mate guard that male in the presence of a female competitor through female-female mounting. When female rats mate guarded, it they displayed more Fos induction within areas known to be involved in pair bonding and stress. Chapter 2 showed that the Fos induction seen within bonding regions was within oxytocin and vasopressin neurons. We also show that oxytocin and vasopressin are important for conditioned mate guarding behavior, by peripherally administering either oxytocin or vasopressin to females prior to their first sexual experience then subsequently testing them 4 days later for mate guarding. Both vasopressin and oxytocin were able to facilitate mate guarding. Chapter 3 explored the contribution of histone methylation to creating the enhanced expression of oxytocin and vasopressin we observed in chapter two. By pharmacologically blocking the action of LSD1 demethylases we were able to show that the enhanced expression of oxytocin and vasopressin are essential for the onset of mate guarding. Females treated with the LSD1 inhibitor failed to display mate guarding and did not show an enhanced expression of oxytocin or vasopressin. Together, these data demonstrate the flexibility within the mating strategy of female rats, and that their first experiences with mating and sexual reward influence the subsequent expression of their mating strategy which is sub served by neuromolecular and epigenetic mechanisms.