Neuroanatomical dichotomy of sexual behaviors in rodents

Abstract

Much of the social behavior in which rodents engage is related to reproduction, such as maintaining a breeding territory, seeking mates, mating, and caring for their young. Rodents belong to the internally fertilizing species that require sexual behavior for reproduction. The dyadic, heterosexual patterns of most mammalian species are sexually dimorphic, but they also share mutual components in both sexes: sexual attraction is reciprocal, sexual initiative is assumed, appetitive behavior is engaged in, and mating involves consummatory and postconsummatory phases in females as well as in males. Serotonin, a phylogenetically ancient molecule, is the most widely distributed neurotransmitter in the brain and its signaling pathways are essential for numerous functions including sexual behavior. Since the late 1960s, brain serotonergic neurotransmission has been considered to exert an inhibitory influence on the neural mechanisms mediating sexual behavior. This contention was based mainly on the observations that a decrease in central serotonergic activity facilitated the elicitation of sexual behavior, whereas an increase in central serotonergic activity attenuated it. However, the discovery of over 14 types of serotonin receptors has added numerous layers of complexity to the study of serotonin and sexual behavior. Evidence shows that, upon activation, certain receptor subtypes facilitate, whereas some others suppress, sexual behavior, as well as sexual arousal and motivation. Furthermore, the role of these receptors has been shown to be different in the male and female sexes. The use of serotonergic pharmacological interventions, mouse strains with genetic polymorphisms causing alterations in the levels of brain serotonin, and animal models with genetic manipulations of various serotonin effectors has helped delineate the fundamental role of this neurotransmitter in the regulation of sexual behavior. This review aims to examine the basics of the components of female and male sexual behavior and the participation of the serotonin system in the modulation of these behaviors, with emphasis on rodents.

Differential serotonergic innervation of the amygdala in bonobos and chimpanzees

“…In human patients and rodent models, treatment with selective serotonin reuptake inhibitors, which act by increasing synaptically available 5-HT, is associated with male sexual dysfunction but no change in sexual motivation (i.e. libido) has been demonstrated (Barrett et al, 2006;Angoa-Pé rez and Kuhn, 2015). The role of 5-HT in regulating sexual behavior in primates is known mostly from pharmacological manipulation of 5-HT neurotransmission, with both facultative and inhibitory responses observed depending on the receptor subtype that is activated (Barrett et al, 2006).…”

Neural Circuit Mechanisms of Social Behavior

“…In male mice, mating involves approach and investigation of the female’s face and anogenital region, emission of USVs, mounting, intromission, and ejaculation (Hull and Dominguez, 2007). On the other hand, female mice display solicitation behavior such as pacing, and undergo postural changes like lordosis behavior (Angoa-Pérez and Kuhn, 2015). In a mating behavioral sequence, both precopulatory and copulatory behaviors are temporally intermixed with constant switching between the two, so the phase distinction is context and time-dependent (Angoa-Pérez and Kuhn, 2015).…”

Serotonergic activation during courtship and aggression in the brown anole,Anolis sagrei

“…Projections of these two nuclei to different sets or types of post-synaptic receptors could explain the simultaneous positive relationship between courtship behaviors and neural activity in the Rsl and negative relationship with activationin the RAsm. Overall, the effects of 5-HT on sexual behaviors are still not fully understood and the effect of 5-HT on sexual behavior even appears to differ between sexes ( Mariana & Kuhn, 2015 ).…”