Increase in sexual motivation throughout adolescence in the cycling female rat

Abstract

Sexual behavior in the female rat is a highly motivated behavior first displayed during adolescence, a developmental period when neural circuits underlying motivation are not mature. This study characterizes the natural development of sexual motivation and behavior of female rats. We compared the incentive value of the male for mid‐adolescent (PNDs:39‐43), late adolescent (PNDs:49‐53), and adult (PNDs:90‐115) cycling females, using a male–female preference task and an ultrasonic vocalization emission test following exposure to a male or female stimulus animal. Furthermore, display of sexual and social behaviors during an interaction with a male or a nonreceptive female was assessed. Mid‐adolescent rats exhibited a reduced preference for the male than adults and performed less attempts to access the male. Unlike late adolescent and adult females, mid‐adolescent rats did not increase their ultrasonic vocalization emission after interacting with a male relative to a female. Although most of the sexual behavior did not differ between groups, mid‐adolescent females showed lower lordosis magnitude and higher levels of play and social investigation during a sexual interaction, giving rise to a unique behavioral profile. Present results indicate that the sexual behavior repertoire is fully displayed by mid‐adolescence, but sexual motivation is low and increases into late adolescence.

Hearing, touching, and multisensory integration during mate choice

“…However, there has been controversy regarding the importance of male calls in female mate choice; while some studies support the importance of male calls (Thomas and Barfield, 1985 ; Gerson et al, 2019 ) eliciting female approach behavior (Seffer et al, 2014 ; Willadsen et al, 2014 ; Berg et al, 2018 , 2021 ; Kisko et al, 2018 , 2020 ), others found that females choose vocalizing vs. non-vocalizing males equally often (Snoeren et al, 2014 ). Despite the contradictory results, it is well accepted that female rats emit more calls when interacting with male vs. female conspecifics (White et al, 1993 ; Armas et al, 2021 ), probably signaling sexual motivation towards the male (Börner et al, 2016 ) and that male USVs can trigger female solicitation behavior (McIntosh et al, 1978 ), including ear wiggling and darting behavior. Solicitation behaviors seem to be rewarding for both sexes (Martínez and Paredes, 2001 ) and increase male sexual arousal, hence activating male mounting behavior with a shorter latency (Chu and Ågmo, 2015b ; Ågmo and Laan, 2022 ) and pointing to a certain choice from the male towards the female.…”

Adolescence and Postpartum: Two Life Periods to Deepen Our Understanding of the Complexity of Female Rat Sexual Behavior

“…As this variable is sensitive to hormonal treatments that modify the sexual motivation of females [89][90][91][92], we evaluated the incentive value of the male for adolescent and adult rats in two motivational tests: a male vs. female preference task [45] (Figure 2A) and 50 kHz USV emission after a brief sexual vs. social interaction [74] (Figure 2B). Interestingly, mid-adolescent rats exhibited a reduced preference for the male compared to adults, and unlike females in later developmental stages, did not perform a greater number of attempts to access the male in this test [45,88]. In addition, these young sexually active females did not increase the emission of 50 kHz USV after a brief interaction with a male relative to an interaction with a female, as late-adolescent and adult rats did [88].…”

“…Despite the lack of differences in proceptive responses and lordosis quotient between these age-groups, the intensity of the lordosis response (how pronounced the dorsiflexion is [89]) was reduced in mid-adolescent females [88]. As this variable is sensitive to hormonal treatments that modify the sexual motivation of females [89][90][91][92], we evaluated the incentive value of the male for adolescent and adult rats in two motivational tests: a male vs. female preference task [45] (Figure 2A) and 50 kHz USV emission after a brief sexual vs. social interaction [74] (Figure 2B).…”

“…The study of the maturation of female rat sexual behavior throughout adolescence, to the best of my knowledge, did not advance much from these initial studies. Recently, a study from our laboratory found that naturally cycling mid-adolescent rats (30-43 postnatal days) show similar expression of proceptive behaviors and maximal lordosis quotient when compared to that displayed by late-adolescent (59-53 postnatal days) and adult (90-110 postnatal days) females [88]. However, this adult-like sexual response of midadolescent rats, unlike adult females, was accompanied by play behavior and high social exploration.…”

Melanocortin 4 receptor signaling in Sim1 neurons permits sexual receptivity in female mice

“…It is also possible that the overall reduction in ambulation by MC4RKO mice impacted their frequency of approaching the male (although see discussion of the behavior of tbMC4R oxt mice below). Additional experimental designs used in rats to gauge female sexual motivation should be employed in future studies, such as social approach chambers comparing interest in intact and gonadectomized males, paced mating chambers, measurement of ultra-sonic vocalizations, conditioned place preference studies, or operant chambers to assess the number of nose pokes a female will exhibit to gain access to a male (67,68).…”