Proceptive Behavior Research Articles

Multiparous ewes have greater mating success when competing with nulliparous ones

The hypothesis of this study was that multiparous ewes are more attractive to rams than nulliparous ewes, leading to more intense courtship and mating displays by rams in competitive environments. Thus, this study aimed to compare the sexual interactions of multiparous or nulliparous estrous ewes tested together or individually with sexually active males. Seven sexually experienced Corriedale rams, 21 multiparous, and 21 nulliparous Corriedale ewes were used. Competitive and individual sexual behavior tests were performed for 3 consecutive days immediately after estrous detection. Seven rams were tested with seven different dyads of one multiparous and one nulliparous female daily, totaling 14 ewes per day. The competitive sexual behavioral test evaluated a ram together in a pen with one multiparous ewe and one nulliparous ewe for 10min. In the individual sexual behavioral test, each ram was tested twice for 10min, with the same multiparous and nulliparous females used in the competitive sexual tests. The sexual behaviors of rams were recorded in both tests, and ewes' behaviors were registered in the competitive sexual tests. During the competitive sexual tests, rams approached, mated, and tended to sniff the multiparous ewes before the nulliparous ewes (p=0.03; p=0.01; p=0.056, respectively). In those tests, rams mated the multiparous ewes more efficiently than nulliparous ones (p=0.002), meaning that rams mounted multiparous fewer times to ejaculate. The number of flehmens and their length were greater in nulliparous than in multiparous (0.01 and 0.002, respectively). The nulliparous ewes urinated more times and tended to do it in greater duration and tended to walk more than the multiparous (p=0.01; p=0.06; p=0.08, respectively). During the individual sexual behavioral tests, rams showed no differences in the sexual behaviors displayed toward multiparous and nulliparous females. In conclusion, multiparous ewes were preferred as sexual partners over nulliparous ewes, with rams showing greater efficiency in ejaculating with multiparous ewes. This increased sexual attractiveness was primarily due to the ewes' attractive signals rather than their proceptive behaviors. However, multiparous and nulliparous ewes were courted and mated similarly when rams had no choice, increasing the likelihood of reproduction in both groups. While nulliparous ewes signaled their reproductive status more frequently through urination, this signal did not compensate for the other signals provided by multiparous ewes, which contributed to their higher sexual attractiveness. These findings offer practical insights, emphasizing the importance of separating multiparous and nulliparous ewes to optimize reproductive outcomes in collective breedings.

Female Mate Choice in Wild Kenyan Blue Monkeys (Cercopithecus mitis).

Female mate choice may drive sexual selection, but discerning whether female behaviors reflect free expression of choice or responses to constraints can be difficult. We investigated the efficacy of female choice in wild blue monkeys using 10 years of behavior and paternity data (N = 178 male-female dyads). Although blue monkeys live modally in one-male polygynous groups, where male-biased intersexual power is expected, females can access multiple potential mates during seasonal male influxes and occasional intergroup encounters. Additionally, extra-group males sire offspring. We examined female resistance rates to male-initiated sexual interactions, and unsolicited proceptive behavior that females directed to males (corrected for male availability). Females seldom resisted male solicitation, but initiated sexual interactions more than males. Females generally preferred residents. Those who preferred non-residents tended to have residents with longer tenures, but neither female parity nor rank influenced the tendency to prefer non-residents vs. residents. The male most solicited by a particular female fathered that female's infant 82% of the time; odds of siring were 26 times higher for most vs. nonpreferred males. Female preference predicted paternity even more strongly among non-resident males, with odds of siring 33 times higher for most vs. nonpreferred non-residents. Neither female rank nor parity influenced her likelihood of having her preferred partner as sire. Paternity by preferred males did not affect infant survival. While we cannot fully discount the effect of male-male competition on paternity, these results suggest that blue monkey females can exercise choice successfully, even in a polygynous mating system.

Kisspeptin administration may promote precopulatory behavior in male rats independently or supplementally to testosterone and contribute to proceptive behavior in female partners, reducing mating failure

Kisspeptin is a peptide that plays an important role through its effects on the hypothalamus-pituitary–gonadal (HPG) axis. It has also been implicated in sexual behavior. The present study investigated whether the relationship between kisspeptin and sexual behavior is independent of the HPG axis, i.e., testosterone. Sexual behavior was examined after the administration of kisspeptin to gonadally intact male rats and gonadectomized male rats that received testosterone supplementation. Other male rats were also observed for sexual behavior once a week from 2 to 5 weeks after gonadectomy and receiving kisspeptin for the sixth postoperative week. Sexual behavior in female rats serving as the partner for each male was also observed. Female rats were not administered kisspeptin in the present study. The results obtained showed that the administration of kisspeptin increased precopulatory behavior in gonadally intact male rats and gonadectomized male rats that received testosterone supplementation and proceptive behavior in their female partners. Precopulatory behavior in males and receptive behavior in females increased, while copulatory behavior in males and receptive behavior in females remained unchanged. Furthermore, the administration of kisspeptin increased precopulatory behavior in gonadectomized males, but did not affect receptive behavior in females. These results suggest that kisspeptin affected males independently and/or supplementally to testosterone, and also that changes in the presence of testosterone in males had an impact on proceptive behavior in their female partners. In conclusion, kisspeptin may involve an as-yet-unidentified neural pathway in sexual desire independently of the HPG axis.

Close bonds and social rank similarities favor non‐random mating in captive stump‐tailed macaques (Macaca arctoides)

AbstractAssortative mating is non‐random mating by the mutual choice of phenotypes or behavioral types. In polygynandrous species, competition for mating by social rank can lead to assortative mating. However, although not an individual trait, social bonds also influence mating opportunities resembling assortative mating. Stump‐tailed macaques form long‐term close bonds and organize in a linear dominance–subordination hierarchy. Therefore, we studied whether the strength of the social bond and rank closeness influenced mating decisions and increased mating opportunities, particularly for low‐ and middle‐ranking animals. Firstly, we observed whether females directed proceptive behavior to close‐bonded or adjacent rank males. Secondly, we measured whether successful copulations were related to the strength of social bonds and close ranking. Thirdly, to ensure that copulations owed mainly to the aforementioned factors, we also evaluated whether sexual coercion was unrelated to social bonds and rank similarities. Finally, we assessed whether close bonds mediated agonistic support to females. The study subjects were 12 adult female and 11 male captive stump‐tailed macaques. We monitored daily females' reproductive status by vaginal cytology. Sexual behavior was recorded by all occurrences sampling and scan sampling to collect the agonistic and affiliative instances required to calculate social ranks, social bond strength, and agonistic support. The results indicated that the probability of females displaying proceptivity increased during the follicular phase toward close‐bonded and high‐ranking males. Copulation chances increased with male–female social bonds and rank closeness. Forced copulation decreased in close‐bonded individuals, while agonistic support increased in close‐ranking strong‐bonded animals. In conclusion, close social bonds and similar social rank result in non‐random mating in stump‐tailed macaques.

Female post-copulatory behavior in a group of olive baboons (Papio anubis) infected by Treponema pallidum.

Pathogens exert a profound and pervasive cost on various aspects of primate sociality and reproduction. In olive baboons (Papio anubis) at Lake Manyara National Park, Tanzania, genital skin ulcers, caused by the bacterium Treponema pallidum subsp. pertenue, are associated with increased female mating avoidance and altered male mating patterns at a pre-copulatory and copulatory level. Beyond this, mating is also comprised of post-copulatory interactions among sexual partners (i.e., copulation calls, darting [post-copulatory sprint away from the male], and post-copulatory grooming). In baboons, female post-copulatory behavior is hypothesized to incite male-male competition, promote subsequent copulations, and/or strengthen the bonds between the mating pairs. Due to a higher reproductive burden (i.e. pregnancy, lactation, infant rearing), females should avoid proceptive behavior after mating to decrease further exposure to potential pathogens. To investigate whether the presence of genital skin ulcers has an impact at the post-copulatory level, we analyzed 517 copulation events of 33 cycling females and 29 males with and without genital skin ulcers. The occurrence of female post-copulatory behaviors was not altered by genital skin ulcerations in males. Similar to other baboon populations, females in our study group were more likely to utter copulation calls after an ejaculatory copulation. The likelihood of darting was higher after ejaculatory copulations and with the presence of copulation calls. Post-copulatory grooming (i.e., occurring within 15 seconds after a copulation) was not frequently observed. Our results indicate that despite the presence of conspicuous signs of disease, female post-copulatory behavior was not affected by the genital health status of the males. This indicates that in our study group, infection cues caused by T. pallidum subsp. pertenue play a major role before and during mating, but not after mating. The post-copulatory behavior of females is most likely affected by physiological or evolutionary constraints other than sexually transmitted infections.

Male-Directed Object Use by Proceptive Female Bearded Capuchin Monkeys (Sapajus libidinosus) in Captivity

Some nonhuman primates use tools to modify the behavior of other animals in social contexts. For example, during their proceptive periods, female bearded capuchins (Sapajus libidinosus) in two wild groups throw stones and push branches toward males, which may function to draw male attention to the females. To further clarify the social and communicative relevance of this behavior, we recorded all occurrences of object use in a captive group (one adult male and four females) at Brasilia Zoo, during 963 h of observation. Additionally, we recorded the occurrence of typical proceptive behaviors and quantified behavioral changes of the male associated with throwing behavior. All females threw objects, such as stones and sticks, at the male (N = 205 events). One of the females also pounded objects near the male (N = 72). The two forms of object use were associated with female proceptivity. Male-directed throws increased the chances of the male changing his behavior, particularly by shifting his attention to the thrower, supporting the hypothesis that throwing at the male function as a communicative act. However, females also used aimed throwing in affiliative contexts (N = 2) and interactions with humans (N = 102) and other animals (N = 61). Thus, our results show that aimed throwing is a flexible behavior, elicited in multiple social contexts and for different purposes. Moreover, our study demonstrates that considering the effects of object use on the behavior of potential targets can help us to understand how primates use objects to mediate communication.

Fertility Desires, Intentions and Behaviour: A Comparative Analysis of Their Consistency

Realisation of childbearing intentions implies couple’s dyadic interaction and proceptivebehaviour. Studies on childbearing intentions and outcomes have rarely considered non-­‐‑use of contraception or ‘proceptive behaviour’ in general as an important mediator offertility outcomes. The traits-­‐‑desires-­‐‑intentions-­‐‑behaviour theory (Miller and Pasta, 1996;Miller et al., 2004; Miller, 2010) expects proceptive behaviour to be the most accuratepredictor of a birth and intentions to be more predictive than desires. We test this theoryusing longitudinal data from the Generations and Gender Surveys from Austria, Franceand Bulgaria (2004–2013) and performing logistic regression models on birth outcomeswhich includes as key explanatory variables different pairwise combinations of desires,intentions and contraceptive (or proceptive) behaviour. The findings show that anindividual’s intention to have a child predicts the birth of a child better than non-­‐‑use ofcontraception, or proceptive behaviour; however, proceptive behaviour is a betterpredictor of a birth than non-­‐‑use of contraception. Finally, perception of the partner’sagreement on having a child now is less predictive than an individual’s intention to havea child within three years. This paper calls for the collection of genuine couple-­‐‑level dataon fertility intentions and behaviour and more refined measures on both contraceptiveand proceptive behaviour.

138 Randel Lecture: Reproductive Behavior – the basis of reproductive success

Abstract In domesticated, promiscuous species like sheep, mate choice is constrained by breeding strategies with limited mate choice. The proportion of rams with limited sexual interest in ewes is nearly 30% of the total number of breeding rams. Rams with low sexual interest detect putative sexual signals from ewes but fail to act in a suitable manner. While a tempered reward mechanism with decreased dopamine synthesis in the mid-brain of low sexually performing rams may partially account for this behavior, how the ewe responds to low-sexually performing rams remained unknown. Ewes are relatively undemonstrative in the expression of sexual behavior. The most widely expressed behavior from the ewe is the increased ambulatory behavior to seek out and affiliation with a ram. The expression of this behavior is estrogen dependent and likely increases the sexual interest of the ram and the reproductive success of the ewe. Rams with low sexual interest do mate and sire lambs. It might be expected that ewe affiliation behavior would increase when the ratio of ewes to rams is high (ie. breeding intensity) or sexual interest is low. This does not appear to be the case since ewes express more proceptive behavior toward rams with greater sexual interest. Ewes spent more time in affiliation with high sexually performing rams (P < 0.001) 57.7% (±3.3) than those expressing low sexual interest (23.8% [± 3.4]). Rams expressing high sexually interest garner more solicitous looks from ewes than do low performing rams. Time in affiliation highly correlated with expression of ram behaviors including number of mounts, total anticipatory, and consummatory behavior. While ewes exhibited increased number of purposeful moves toward high performing rams, movement away from the ram to did not differ by expression of male behavior. In conclusion, ewe behavior does not compensate for low sexual interest from the ram and would not be expected to contribute to the reproductive success of rams expressing low sexual interest.

Body movement as an indicator of proceptive behavior in nurse sharks (Ginglymostoma cirratum)

Nurse sharks are vulnerable of extinction in Brazil. Although its reproductive behavioral repertoire is already known, including indications that females are not passive to the attempts of males, no indication of proceptive behavior of females of this species is known. Considering that proceptive behavior is what initiates or increases the probability of a male exhibiting sexual behaviors directed at a female, the present study carried out behavioral observations in two groups of nurse sharks in reproductive period to identify possible proceptive behaviors. The present work identified a new behavior, here referred to as Body Movement (BM), as an indicator of proceptivity. This behavior corresponded on average to 47.68% of the reproductive behaviors performed by the females and its occurrence was positively correlated (r = 0.5143341 / p = 0.04152 - Spearman) with the occurrence of socio-reproductive behaviors of males. Being able to identify signs of proceptivity in animals is important to understand the reproductive context in which a group is found and to allow greater attention to animals that are able to reproduce, in order to create more efficient reproductive management programs to develop long-term sustainable population management.

The effects of 28-day early-life exposure to triphenyl phosphate (TPhP) on odor preference and sexual behavior in female rats.

Many chemical substances are detectable in house dust, and they are consequently taken into our bodies via the mouth and nose. Triphenyl phosphate (TPhP), a flame retardant that has an estrogen‐like effect in vitro, is present in house dust at high concentrations. Estrogen exposure during development has significant influences on reproductive behavior in rodents, and its effects persist until maturity. In the present study, we investigated the effect of early life exposure to TPhP on the reproductive behavior of female rats. Oral treatment with TPhP (25 or 250 mg/kg), ethinyl estradiol (EE; 15 μg/kg) as a positive control, or sesame oil as a negative control, were given to female rats (from birth to 28 days of age). The 8‐week‐old rats were bilaterally ovariectomized. At 12–15 weeks of age, the rats were subjected to odor preference and sexual behavior tests. In the odor preference test, the oil group showed significantly higher preference for male odor than female odor, but the low‐dose TPhP treatment group lost the preference for male odor, indicating a possible outcome of early life TPhP exposure on sexual recognition. In the sexual behavior test, both the EE and TPhP treatment groups displayed significantly less proceptive behavior. These results suggest that early life exposure to TPhP disturbs the normal sexual behavior of female rats.

The reduction in sexual behavior of adult female rats exposed to immune stress in the neonatal period is associated with reduced hypothalamic progesterone receptor expression

PurposeWe examined the mechanism by which neonatal immune stress reduces the sexual behavior of female rats in adulthood. MethodsNeonatal female rats were randomly divided into 3 groups: control (n = 11), postnatal day 10 lipopolysaccharide (PND10LPS) (n = 23), and PND25LPS (n = 11) groups, which received intraperitoneal injections of LPS (100 μg/kg) or saline on PND10 and 25. Daily inspections of the vaginal opening (VO) were performed from PND27 to PND37. Thereafter, the frequency of estrus was assessed for 15 days. Female rats (at 11–12 weeks of age) were placed in a cage with male rats, and their sexual behavior was monitored for 30 min. The hypothalamic mRNA expression levels of factors related to sexual behavior were examined via real-time PCR. ResultsVO occurred later and the frequency of estrus was lower in the PND10LPS group compared to the control group. The number of lordosis behaviors and the total number of mounts performed by male partners were lower in the PND10LPS and PND25LPS groups than in the control group. Acceptability: The lordosis quotient and lordosis rating were lower in the PND10LPS group than in the control group. Proceptive behavior: the number of ear wiggling events was lower in the PND10LPS group than in the other groups, and the number of hops/darts was lower in the PND10LPS group than in the control group. The hypothalamic mRNA expression level of progesterone receptors (PR)A + B was lower in the PND10LPS group than in the control group, and the hypothalamic PRB mRNA expression level was lower in the PND10LPS and PND25LPS groups than in the control group. ConclusionNeonatal immune stress impeded sexual behavior and hypothalamic PR mRNA expression in female rats. Decreased progesterone activity in the hypothalamus might explain the reduction in sexual behavior seen in these rats.

Ovarian Hormones Mediate Changes in Adaptive Choice and Motivation in Female Rats.

In female rodents, sexual receptivity is coordinated with cyclic changes in the release of gonadal hormones. Increases in estradiol (E) and progesterone (P) during proestrus and estrus not only induce ovulation but also modulate behaviors that increase the likelihood that the female will find a mate and reproduce. This includes changes in receptive behaviors, such as lordosis, as well as changes in appetitive or proceptive behaviors, including motivation. Interestingly, the direction of these changes in motivation is dependent on the type of reward that is being pursued. While induction of sexual receptivity by E and P increases motivation for access to a male, motivation for a palatable food reward is decreased. These concurrent changes may facilitate adaptive choice across the estrous cycle; females bias their choice for sex when fertilization is most likely to occur, but for food when copulation is unlikely to result in impregnation. In order to test this hypothesis, we developed a novel paradigm to measure the motivated choice between a palatable food reward and access to a male conspecific. Ovariectomized, hormone primed females were trained to operantly respond for both food and sex on a fixed interval (FI) schedule. After training, unprimed and primed females were tested in a chamber that allows them to choose between food and sex while still requiring responding on the FI schedule for reach reward. From this we can not only determine the impact of hormone priming on female choice for food or sex, but also how this is reflected by changes in motivation for each specific reward, as measured by the average number of responses made during each fixed interval. Induction of sexual receptivity by hormone priming biases choice toward sex over food and this change is accompanied by an increase in motivation for sex but a decrease in motivation for food. This work provides evidence in support of a novel framework for understanding how the release of ovarian hormones over the course of the estrous cycle modulates adaptive behavioral choice in females by directly assessing motivation via operant responding when multiple rewards are available.

Two thalidomide analogs induce persistent estrous behavior and inhibit uterus contractility in rats: The central role of cAMP

The effects of 4NO2PDPMe and 4APDPMe, which are thalidomide (Tha) analogs that act as selective phosphodiesterase (PDE-4) inhibitors, on estrous behavior (lordosis and proceptive behaviors) and on uterine contraction were studied in ovariectomized (OVX) estrogen-primed Sprague Dawley (SD) and in intact non-pregnant Wistar rats, respectively. We found that intracerebroventricular (ICV) infusion of either 4NO2PDPMe or 4APDPMe (20 to 80 μg) stimulated intense lordosis and proceptive behavior in response to mounts from a sexually active male, within the first 4 h after infusion, and persisting for up to 24 h. Inhibitors of the progesterone receptor (RU486, administered subcutaneously), the estrogen receptor (tamoxifen, ICV), the adenylate cyclase (AC)/ cyclic AMP (cAMP)/protein kinase A (PKA) pathway (administered ICV), and the mitogen activated protein kinase (MAPK) pathway (administered ICV) significantly decreased lordosis and proceptive behavior induced by Tha analogs. Uterine contractility studies showed that Tha analogs inhibited both the K+- and the Ca2+-induced tonic contractions in rat uterus. Tha analogs were equally effective, but 4APDPMe was more potent than 4NO2PDPMe. These results strongly suggest the central role of cAMP in both processes, sexual behavior, and uterine relaxation, and suggest that Tha analogs may also act as Ca2+-channel blockers.

Effects of intracerebroventricular arginine vasotocin on a female amphibian proceptive behavior.

Mate choice decisions of animals show significant variability-both among and within individuals. Clearly, such variability can profoundly impact individual fitness, as well as subtly alter sexual selection processes, but we know little about the neural mechanisms underlying such variability. We examined the influence of the neuropeptide arginine vasotocin (AVT) on the strength of attraction of female gray treefrogs (Hyla versicolor) showing positive phonotaxis to the call of a conspecific male. Female treefrogs received intracerebroventricular injections with either saline, AVT (five doses), or the AVT receptor antagonist Manning compound (two doses). By 30min after injection, AVT significantly increased the speed with which females approached the speaker, at doses of 1, 10 and 50ng per frog. At the highest dose, the average speed was doubled. The AVT antagonist significantly inhibited phonotaxis at both doses (50 and 100ng). The effects of AVT on treefrog phonotaxis were shorter lived (disappearing within 60-90min), compared to Manning compound (effects persisted at least 90min). These findings support the hypothesis that endogenous AVT is critical to the display of female phonotaxis behavior. AVT may thus contribute to variability in female mate choices by modulating proceptive behaviors.

Ewes express increased proceptive behavior toward high-sexually active rams

Variable expression of male reproductive behavior has been observed in all species studied. Approximately 25% of male sheep exhibit low sexual interest, but usually mate and have limited numbers of offspring. In domesticated, promiscuous species like sheep, the female may have mate preference, but mate choice is usually constrained by breeding strategies. It was hypothesized that when mate choice is limited, ewes would exhibit more proceptive behavior toward rams with low sexual interest to ensure reproductive success. Recorded serving capacity tests (n = 56) were utilized for this analysis. Rams were individually exposed to two ewes in estrus with behavior recorded for 20 min. From those recordings, a 10 min time period was utilized to assess ewe proceptive behavior. Ram anticipatory and consumatory behaviors were recorded. Anticpatory behaviors included ano-genitial sniffs, vocalization, fore-leg kicks, head butts, and nudges. Consumatory behavior included mount attempts, mounts, and ejaculations. Rams were categorized as high performing if they achieved two or more mounts during the 10 min period. Ewe behavior was determined by the number of solicitation looks and movements toward and away from the ram. During the 10 min of observed behavior, time spent in close proximity (less than 0.3 m) to the ram was determined and considered time in affiliation with the ram. Percent of time spent in affiliation with high sexually performing rams was greater (P < 0.001) 57.7% (±3.3) than when exposed to rams exhibiting low sexual behavior (23.8% [±3.4]). Affiliation time was highly correlated (P < 0.001; r2 ≥ 0.6) with ram behaviors: number of mounts, total anticipatory, and consummatory behavior. High sexually performing rams garnered more (P < 0.001) solicitous looks from ewe than did low performing rams. Ewes exhibited increased number of purposeful moves toward (P = 0.02), but not away (P = 0.58) from, high performing rams. These data indicate that ewes express more proceptive behavior toward rams expressing greater sexual interest. In conclusion, ewe behavior does not compensate for low sexual interest from the ram and would not be expected to contribute to the reproductive success of rams expressing low sexual interest.

Sexually experienced, but not naïve, female rats show a conditioned object preference (COP) for mating after a single training trial

Female rats with mating experience spend more time with the male rat, exhibit shorter contact-return latency to intromission, and display more proceptive behaviors in the male rat's compartment than during the first mating experience. The present study tested 1) whether mating induced conditioned object preference (COP) is possible with a single conditioning trial and 2) whether a preference is induced for an object associated with the first mating encounter or the fifth mating encounter in female rats. Ovariectomized, Long-Evans female rats were primed with estradiol benzoate + progesterone and either exposed to an empty paced mating chamber for 15 min (Naïve) or received a 15 intromission test of paced mating behavior (Experienced) on four separate occasions before undergoing the COP procedure. Experienced, but not Naïve, female rats developed a COP for a single mating bout, indicating that mating is highly rewarding for sexually experienced female rats. The findings raise questions about the effect of sexual experience on reward regions in the brain, the responsiveness of genital tissue, and learning mechanisms.

The tail in tropical hair ewes (Ovis aries) that are in estrus is used as a proceptive signal and favors ram’ copulation

Two experiments were performed to determine if the tail has a role: 1) in proceptive behavior, and 2) in facilitating copulation in hair sheep. The movements and position of the tail of estrous and non-estrous ewes in response to male courtship were compared in the first study. In the second study, the courtship of rams and mating behavior directed towards tailed or tail-docked, in estrus or diestrus ewes, were compared. Both experiments were conducted with restrained ewes during 3 min assessment periods. In Experiment 1, tail movements occurred in short episodes in response to physical contact of the male, but the rest of the time the tail of non-estrous ewes was drawn inward to the body, while in estrous ewes it simply hung naturally straight downward. Ewes in estrus had many tail moving episodes (P <0.001) with more movements per episode (P <0.001), that were of greater amplitude (P <0.001) and greater elevation in angle from the body (P <0.001) than in non-estrus ewes. In Experiment 2, ejaculation latencies with non-estrous ewes were longer than with estrous ewes (P <0.0001), and rams had more attempts to mount (P = 0.008), and more completed mounts (P = 0.0003) in non-estrous than estrous ewes. In addition, rams ejaculated more times (P <0.0001), and had a greater ejaculations/(mounts + ejaculations) ratio in estrous than non-estrous ewes (P <0.0001). More rams also had anal intromissions in docked than in intact tail-ewes (P = 0.0002). In conclusion, movements and position of the tail of estrous ewes is a primary component of the proceptive behavior that facilitates mating and serves as a physical barrier to avoid anal intromissions in hair sheep.

Early postnatal treatment with clomipramine induces female sexual behavior and estrous cycle impairment

Administration of clomipramine (CMI), a tricyclic antidepressant, in early stages of development in rats, is considered an animal model for the study of depression. This pharmacological manipulation has induced behavioral and physiological alterations, i.e., less pleasure-seeking behaviors, despair, hyperactivity, cognitive dysfunction, alterations in neurotransmitter systems and in HPA axis. These abnormalities in adult male rats are similar to the symptoms observed in major depressive disorders. One of the main pleasure-seeking behaviors affected in male rats treated with CMI is sexual behavior. However, to date, no effects of early postnatal CMI treatment have been reported on female reproductive cyclicity and sexual behavior. Therefore, we explored CMI administration in early life (8–21 PN) on the estrous cycle and sexual behavior of adult female rats. Compared to the rats in the early postnatal saline treatment (CTRL group), the CMI rats had fewer estrous cycles, fewer days in the estrous stage, and longer cycles during a 20-day period of vaginal cytology analysis. On the behavioral test, the CMI rats displayed fewer proceptive behaviors (hopping, darting) and had lower lordosis quotients. Also, they usually failed to display lordosis and only rarely manifested marginal or normal lordosis. In contrast, the CTRL rats tended to display normal lordosis. These results suggest that early postnatal CMI treatment caused long-term disruptions of the estrous cycle and female sexual behavior, perhaps by alteration in the hypothalamic-pituitary-gonadal (HPG) axes and in neuronal circuits involved in the regulation of the performance and motivational of sexual behavior as the noradrenergic and serotonergic systems.

A study of time- and sex-dependent effects of vortioxetine on rat sexual behavior: Possible roles of direct receptor modulation

Treatment-related sexual dysfunction is a common side effect of antidepressants and contributes to patient non-compliance or treatment cessation. However, the multimodal antidepressant, vortioxetine, demonstrates low sexual side effects in depressed patients. To investigate the mechanisms involved, sexual behavior was assessed in male and female rats after acute, and repeated (7 and 14 days) treatment with vortioxetine, flesinoxan (a 5-HT1A receptor agonist), CP-94253 (a 5-HT1B receptor agonist), or ondansetron (a 5-HT3 receptor antagonist). These selective ligands were chosen to simulate vortioxetine's direct modulation of these receptors. Paroxetine was also included in the male study. Acute and repeated treatment with vortioxetine at doses corresponding to clinical levels (based on serotonin transporter occupancy) had minimal effects on sexual behavior in male and female rats. High dose vortioxetine plus flesinoxan (to mimic predicted clinical levels of 5-HT1A receptor occupancy by vortioxetine) facilitated male rat sexual behavior (acutely) while inhibiting female rat proceptive behavior (both acutely and after 14 days treatment). The selective serotonin reuptake inhibitor, paroxetine, inhibited male sexual behavior after repeated administration (7 and 14 days). Flesinoxan alone facilitated male sexual behavior acutely while inhibiting female rat proceptive behavior after repeated administration (7 and 14 days). CP-94253 inhibited sexual behavior in both male and female rats after repeated administration. Ondansetron had no effect on sexual behavior. These findings underline the complex serotonergic regulation of sexual behavior and indicate that the low sexual side effects of vortioxetine found in clinical studies are likely associated with its direct modulation of serotonin receptors.

Methamphetamine and Ovarian Steroid Responsive Cells in the Posteriodorsal Medial Amygdala are Required for Methamphetamine-enhanced Proceptive Behaviors

Methamphetamine (Meth) is a psychomotor stimulant strongly associated with increases in sexual drive and impulse in both men and women. These changes in sexual motivation have a greater impact on women due to their likelihood of facing the greater burden of unplanned pregnancies, as well as increased risk for psychiatric co-morbidities such as depression. We have previously established a rodent model of Meth-induced increases in sexual motivation. Using this model, we have identified the posteriodorsal medial amygdala (MePD) via excitotoxic lesion studies as a necessary nucleus in Meth-facilitated female sexual motivation. While lesion studies give us insight into key nuclei that may be targets of Meth action, such an approach does not give insight into the identity of the specific MePD neurons or neural circuitry involved in Meth-induced increases in proceptive behaviors. Using the DAUN02 inactivation method, a recently established technique for removing behaviorally relevant cell populations, we present evidence that the ovarian steroid/Meth responsive cells in the MePD are necessary for Meth-induced facilitation of proceptive behaviors. These findings form the basis for future work that will allow for the classification of neuronal subtypes involved in the MePD’s modulation of proceptive behavior as well as a stronger understanding of the neurocircuitry of female sexual motivation.