Receptive Females Research Articles

A neural pathway underlying hunger modulation of sexual receptivity in Drosophila females

Accepting or rejecting a mate is one of the most crucial decisions a female will make, especially when faced with food shortage. Previous studies have identified the core neural circuity from sensing male courtship or mating status to decision-making for sexual receptivity in Drosophila females, but how hunger and satiety states modulate female receptivity is poorly understood. Here, we identify the neural circuit and its neuromodulation underlying the hunger modulation of female receptivity. We find that adipokinetic hormone receptor (AkhR)-expressing neurons inhibit sexual receptivity in a starvation-dependent manner. AkhR neurons are octopaminergic and act on a subset of Octβ1R-expressing LH421 neurons. Knocking down Octβ1R expression in LH421 neurons eliminates starvation-induced suppression of female receptivity. We further find that LH421 neurons inhibit the sex-promoting pC1 neurons via GABA-resistant to dieldrin (Rdl) signaling. pC1 neurons also integrate courtship stimulation and mating status and thus serve as a common integrator of multiple internal and external cues for decision-making.

New study to verify predictive validity criteria in an animal model for evaluating premature ejaculation: the impact of sertraline and fluoxetine

Premature ejaculation (PE) is a common sexual dysfunction worldwide, and animal models are used to characterize it. We developed a paradigm called the multiple partner choice arena (MPCA), consisting of 4 acrylic cylinders placed crosswise. Each cylinder contains a sexually experienced male rat, and a receptive female rat resides in the central space, able to choose any cylinder for copulation. We have suggested the MPCA as an animal model for assessing PE be-cause male rats in this paradigm display behavior similar to PE in men, achieving ejaculation in less time. This study aims to demonstrate whether the MPCA satisfies the predictive validity criterion, in which the effects of drugs in the animal model should closely resemble those observed in human medical disorders, such as PE. We investigated the effect of 2 SSRIs (SSRI), sertraline and fluoxetine, on male rats' rapid ejaculation in the MPCA. Two groups of male rats (n=8) were tested: saline, sertraline, and fluoxetine. Weekly doses of 1, 3, and 10 mg/kg/day for sertraline and fluoxetine were administered, while the saline group received only the vehicle. Each test involved four males from the same group, treated with identical drug doses, until achieving the first ejaculation in the MPCA. Fluoxetine and sertraline, at the 10 mg/kg dose, significantly prolonged the ejaculation latency. For this reason, the MPCA satisfies the predictive validity criterion as an animal model of PE.

GABAergic signaling shapes multiple aspects of Drosophila courtship motor behavior

Inhibitory neurons are essential for orchestrating and structuring behavior. We use one of the best studied behaviors in Drosophila, male courtship, to analyze how inhibitory, GABAergic neurons shape the different steps of this multifaceted motor sequence. RNAi-mediated knockdown of the GABA-producing enzyme GAD1 and the ionotropic receptor Rdl in sex specific, fruitless expressing neurons in the ventral nerve cord causes uncoordinated and futile copulation attempts, defects in wing extension choice and severe alterations of courtship song. Altered song of GABA depleted males fails to stimulate female receptivity, but rescue of song patterning alone is not sufficient to rescue male mating success. Knockdown of GAD1 and Rdl in male brain circuits abolishes courtship conditioning. We characterize the around 220 neurons coexpressing GAD1 and Fruitless in the Drosophila male nervous system and propose inhibitory circuit motifs underlying key features of courtship behavior based on the observed phenotypes.

Identification of sources of male sterility in the Colombian Coffee Collection for the genetic improvement of Coffea arabica L.

In coffee (Coffea arabica L.), male sterility is a prerequisite for the exploitation of heterosis since it provides an efficient and reliable method for the production of hybrid seeds. Given its relevance, the objective of this study was to identify male-sterile genotypes within the Colombian Coffee Collection that can be used in genetic improvement. For this purpose, Ethiopian germplasm and progenies derived from hybrids between C. arabica x C. canephora were explored between 2017 and 2021. In the first stage, genotypes without visual presence of pollen were preselected in the field, followed by selection through staining and verification of male sterility and female fertility through directed crosses (directed, reciprocal and selfing). In this stage, 9,753 trees were explored, preselecting 2.4% due to visual absence of pollen. The staining of structures allowed us to confirm the lack or sporadic production of pollen in 23 individuals of Ethiopian origin. The results of the directed crosses led to the identification of 11 male-sterile and 12 partially male-sterile genotypes belonging to 15 accessions. In all cases, the individuals were characterized by the presence of anthers but with an absence or low content of pollen, which is why the male sterility is possibly of the sporogenic type. The female receptivity values were between 2.9% and 72.6%, being higher than 30% in five genotypes. These genotypes are a valuable tool for the genetic improvement of C. arabica with the potential to facilitate the use of heterosis and to allow a deeper understanding the development of male gametophytes in the species.

Early Postnatal Experience Modifies Activation of the Pituitary Testicular Complex in Male House Mice (Mus Musculus) Exposed to the Odor of Receptive Con- and Heterospecific Females

For the first time, it was shown that activation of the pituitary–testicular complex in male house mice exposed to the odor of receptive females of their own and closely related species was modified under the influence of early postnatal experience and the maternal environment. We have confirmed associated formation of behavioral and physiological mechanisms of precopulatory isolation in early ontogenesis. The serum levels of free testosterone in males of closely related species M. spicilegus and M. m. wagneri differ, it is significantly lower in mound-building mice. In males fostered by a conspecific female, the level of free testosterone was significantly lower when exposed to a heterospecific female odor in comparison with a conspecific odor. The rearing of M. m. wagneri males by females of a closely related species led to a decrease in the testosterone response caused by exposure to female chemosignals (both con- and heterospecific) and to the absence of differences in the serum level of free testosterone when exposed to the odor of a female of their own or closely related species. These results indicate that the rearing conditions had a significant influence on the formation of hormonal mechanisms of reproductive isolation.

Receptivity and Remating Propensity in Female Spodoptera litura (Fabricius) after Mating with an Irradiated Male or Its F1 Male Progeny.

The 'Inherited or F1 sterility technique' (IS), using sub-sterilized male moths, is a widely proposed pest management tool for Lepidoptera pests in general, and the tobacco cutworm Spodoptera litura (Fabr.) in particular. However, the multiple mating tendency of female moths and the ejaculate quality of male moths might influence the efficiency of this technique. Reduced ejaculate quality was observed in irradiated males, as evidenced by radiation's impact on certain bio-parameters, such as the weight of the spermatophores and their protein content, sperm count, the molecular expression of the sex peptide receptor (SPR) and egg fertility, with a greater impact in F1 male progeny. During the remating of females with untreated males, irrespective of the irradiation status of the first male, there was an increase in calling behavior, remating propensity and fertility in females, with a larger time gap between consecutive matings. The ability of F1 male progeny to check remating propensity in females 24 h after the initial mating was lower than that of unirradiated males. Partially sterile (130 Gy) males were as successful as unirradiated males in inducing the level of mating refractoriness in females. Decreased ejaculate quality in F1 male progeny could be associated with increased female receptivity during remating. Understanding the influence of male moth irradiation, insemination quality and post (initial)-mating intervals on the remating behavior of normal female moths and induced sterility might help in simulation modeling and optimizing IS insect programs.

Maternal neglect alters reward-anticipatory behavior, social status stability, and reward circuit activation in adult male rats.

Adverse early life experiences affect neuronal growth and maturation of reward circuits that modify behavior under reward predicting conditions. Previous studies demonstrate that rats undergoing denial of expected reward in the form of maternal contact (DER-animal model of maternal neglect) during early post-natal life developed anhedonia, aggressive play-fight behaviors and aberrant prefrontal cortex structure and neurochemistry. Although many studies revealed social deficiency following early-life stress most reports focus on individual animal tasks. Thus, attention needs to be given on the social effects during group tasks in animals afflicted by early life adversity. To investigate the potential impact of the DER experience on the manifestation of behavioral responses induced by natural rewards, we evaluated: 1) naïve adult male sexual preference and performance, and 2) anticipatory behavior during a group 2-phase food anticipation learning task composed of a context-dependent and a cue-dependent learning period. DER rats efficiently spent time in the vicinity of and initiated sexual intercourse with receptive females suggesting an intact sexual reward motivation and consummation. Interestingly, during the context-dependent phase of food anticipation training DER rats displayed a modified exploratory activity and lower overall reward-context association. Moreover, during the cue-dependent phase DER rats displayed a mild deficit in context-reward association while increased cue-dependent locomotion. Additionally, DER rats displayed unstable food access priority following food presentation. These abnormal behaviours were accompanied by overactivation of the ventral prefrontal cortex and nucleus accumbens, as assessed by pCREB levels. Collectively, these data show that the neonatal DER experience resulted in adulthood in altered activation of the reward circuitry, interfered with the normal formation of context-reward associations, and disrupted normal reward access hierarchy formation. These findings provide additional evidence to the deleterious effects of early life adversity on reward system, social hierarchy formation, and brain function.

Bush-crickets with very special ears and songs – review of the East African Phaneropterinae genus Dioncomena Brunner von Wattenwyl, 1878, with notes on its biogeography and the description of new species

This study focuses on the genus Dioncomena and its acoustics, particularly the unique songs produced by male Dioncomena that consist of several distinct elements in a fixed sequence, culminating in a coda that typically elicits a response from a receptive female. We also examine the inflated pronotal lobes, which we term prebullae, that are prominently developed in some Dioncomena species but not in others. We discuss the role of prebullae in the context of acoustic communication in Dioncomena and other related Phaneropterini genera that have similar lateral pronotal lobes. We found that prebullae size is correlated with habitat distribution, with larger prebullae occurring in isolated species while aggregation-prone species have smaller or less pronounced prebullae. Using micro-computer tomography we show sexual dimorphism in the 3D geometry of the acoustic tracheae, being larger in the male. Interestingly, the tracheae are coupled by a septum, like in field crickets, which suggests potential cross talk. We define three groups of Dioncomena based on altitude preferences, ecology, color patterns, and songs: the jagoi-, tanneri-, and ornata-groups. We describe the songs of several species, including newly identified species such as D. flavoviridissp. nov., D. magomberasp. nov., D. ngurumontanasp. nov., D. sanjesp. nov., D. tanneri, D. versicolorsp. nov., and D. zernyi. We also provide information on the nymphs, development time, and mating behavior of various species reared in the laboratory, shedding light on their phenology and adaptations to their habitats.

EARLY POSTNATAL EXPERIENCE MODIFIES ACTIVATION OF THE PITUITARY-TESTICULAR COMPLEX IN MALE HOUSE MICE (<i>MUS MUSCULUS)</i> EXPOSED TO THE ODOR OF RECEPTIVE CON- AND HETEROSPECIFIC FEMALES

For the first time, data were obtained proving the modification of the activation of the pituitary-testicular complex of male house mice under the influence of early postnatal experience and the maternal environment when exposed to the odor of receptive females of their own and closely related species. We have confirmed the conjugacy of the formation of behavioral and physiological mechanisms of precopulatory isolation in early ontogenesis. The serum level of free testosterone in males of closely related species M. spicilegus and M. m. wagneri differ, it is significantly lower in mound-building mice. The level of free testosterone of males fostered by a conspecific female was significantly lower when they exposed a heterospecific in comparison with a conspecific female odor. The rearing of M. m. wagneri males by females of a closely related species caused a decrease in the testosterone response of males to the exposure of chemosignals from a female (both con-and heterospecific) and led to the absence of differences in the serum level of free testosterone when they exposed to the odor of a female of their own or closely related species. The data obtained indicate a significant influence of the rearing conditions on the formation of hormonal mechanisms of reproductive isolation.

Behavior, Neural Structure, and Metabolism in Adult Male Mice Exposed to Environmentally Relevant Doses of Di(2-ethylhexyl) Phthalate Alone or in a Phthalate Mixture.

We have previously shown that chronic exposure of adult male mice to low doses of di(2-ethylhexyl) phthalate (DEHP) altered male sexual behavior and induced down-regulation of the androgen receptor (AR) in the neural circuitry controlling this behavior. The cellular mechanisms induced by chronic exposure of adult male mice to low doses of DEHP alone or in an environmental phthalate mixture were studied. Two-month-old C57BL/6J males were exposed orally for 8 wk to DEHP alone (0, 5, or ) or to DEHP () in a phthalate mixture. Behavior, dendritic density per length, pre-/postsynaptic markers, synapse ultrastructure, and bioenergetic activity were analyzed. Mice exposed to DEHP either alone or in a phthalate mixture differed in mating, emission of ultrasonic vocalizations, and the ability to attract receptive females in urinary preference tests from control mice. Analyses in the medial preoptic area, the key hypothalamic region involved in male sexual behavior, showed lower dendritic spine density and protein levels of glutamate receptors and differences in other postsynaptic components and presynaptic markers between the treated groups. Ultrastructural observation of dendritic synapses by electron microscopy showed comparable morphology between the treated groups. Metabolic analyses highlighted differences in hypothalamic metabolites of males exposed to DEHP alone or in a phthalate mixture compared to control mice. These differences included lower tryptophan and higher levels, respectively, a precursor and end product of the kynurenine pathway of tryptophan metabolism. The protein amounts of the xenobiotic aryl hydrocarbon receptor, one of the targets of this metabolic pathway and known negative regulator of the AR, were higher in the medial preoptic area of exposed male mice. Differences in behavior of male mice exposed to environmental doses of phthalates were associated with differences in neural structure and metabolism, with possibly a key role of the kynurenine pathway of tryptophan metabolism in the effects mediated by these substances. https://doi.org/10.1289/EHP11514.

Hormonal responses to mating competition in male Tonkean macaques

Glucocorticoid and androgen hormones play a prominent role in male reproductive effort. Their production usually increases in non-human primates during mating competition, which may include rivalry for access to receptive females, struggles for high dominance rank, or social pressure on low-ranking individuals. It is generally assumed that glucocorticoids and androgens are associated with mating challenges rather than dominance status, but the involvement of multiple factors makes it difficult to disentangle the two. In this regard, Tonkean macaques provide a suitable model because they are characterized by relaxed dominance and year-round breeding, meaning that there is typically no more than one receptive female in a group, and thus first-ranking males can easily monopolize her. We studied two captive groups of Tonkean macaques over an 80-month period, recording the reproductive status of females, collecting urine from males and sampling behaviors in both sexes. Male urinary hormone concentrations could be affected by increased competition caused by the mating period, the number of males and the degree of female attractiveness. The highest increases in androgens were recorded in males performing female mate-guarding. Despite the importance of dominance status in determining which males can mate, we found no significant effect of male rank on glucocorticoids and only a marginal effect on androgens during mate-guarding. Both types of hormones were more directly involved in the mating effort of males than in their dominance status. Our results show that their function can be understood in light of the particular competitive needs generated by the species-specific social system.

Changes in social, sexual, and hedonic behaviors in rats in response to stress and restoration by a negative allosteric modulator of α5-subunit containing GABA receptor

Major depressive disorder (MDD) is a debilitating and costly human condition. Treatment for MDD relies heavily on the use of antidepressants that are slow to produce mood-related changes and are not effective in all patients, such as selective serotonin reuptake inhibitors (SSRIs). Several novel compounds, including negative allosteric modulators of GABA-A receptors containing the α5-subunit (GABA-NAMs), are under investigation for potential fast acting therapeutic use in MDD. Preclinical evidence that these compounds produce a rapid antidepressant-like response comes primarily from simple tests of escape behavior and preference for rewarding stimuli after chronic stress. To increase the ethological relevance of these compounds, we tested the hypothesis that the GABA-NAM, L-655,708, would produce an antidepressant-like response in more complex stress-sensitive social and sex behaviors, which are of relevance to the symptoms of human depression. In male rats subjected to chronic restraint stress, injection of L-655,708 increased reward in a sexual conditioned place preference task, increased male sexual activity with a receptive female, and re-established male social dominance hierarchies within 24 h. We also report increased sucrose preference in the social defeat stress (SDS) model of depression following GABA-NAM administration, demonstrating that its antidepressant-like actions are independent of the type of chronic stress administered. This work extends the impact of GABA-NAMs beyond traditional tests of anhedonia and further supports the development of alpha5 subunit-selective GABA-NAMs as a potential fast-acting therapeutic approach for treating human MDD.

Effects of the aqueous extract of Pycnanthus angolensis (Myristicaceae) on male rat sexual behavior and nitric oxide release

Erectile dysfunction is a major public health problem leading to harmful consequences for couples. Hence the need to find adequate treatments using medicinal plants such as Pycnanthus angolensis, a Cameroonian plant used to treat erectile dysfunction. The effects of aqueous extract of Pycnanthus angolensis wood were evaluated on male rat sexual behavior and nitric oxide release. Adult male Wistar rats were divided into 4 groups of 5 each that included a group receiving orally: distilled water (10 ml/Kg BW), plant extract treatment (43 or 86 or 172 mg/kg BW). Sexual behaviors were monitored on days 1, 4, 7, and 14 by pairing male rats to receptive females and nitric oxide levels were assessed in penile homogenate. At the end of the 14 days of treatment, rats were killed and sexual organs weighed. No significant effect was observed on sexual organs weights. When administered at a dose of 43 mg/Kg, body weight; the plant extract significantly increased (p<0.05) the sexual performance as well as the libido of male rats. Nitric oxide release was significantly increased (p<0.05) in that group of extract-treated rats, while compared to the control group. The study demonstrates that Pycnanthus angolensis is a medicinal plant which can enhance the sexual behaviors of male rat. Hence, it can be used for the management of erectile dysfunction, mainly at a dose of 43 mg/Kg, body weight.

Characterizing Physical Interactions between Male and Female Mosquitoes (Aedes aegypti) in Relation to Female Receptivity and Insemination Outcomes Using a Hydrophobic Fluorescent Dye.

Aedes aegypti, the yellow fever mosquito, presents a major threat to human health across the globe as a vector of disease-causing pathogens. Females of this species generally mate only once. From this single mating event, the female stores sufficient sperm to fertilize the multiple clutches of eggs produced during her lifetime. Mating causes dramatic changes in the female's behavior and physiology, including a lifetime suppression of her mating receptivity. Female rejection behaviors include male avoidance, abdominal twisting, wing-flicking, kicking, and not opening vaginal plates or extruding the ovipositor. Many of these events occur on a scale that is too miniscule or fast to see by eye, so high-resolution videography has been used to observe these behaviors instead. However, videography can be labor intensive, require specialized equipment, and often requires restrained animals. We used an efficient, low-cost method to record physical contact between males and females during attempted and successful mating, determined by recording spermathecal filling after dissection. A hydrophobic oil-based fluorescent dye can be applied to the abdominal tip of one animal and can be subsequently transferred to the genitalia of animals of the opposite sex when genital contact occurs. Our data indicate that male mosquitoes make high levels of contact with both receptive and unreceptive females and that males attempt to mate with more females than they successfully inseminate. Female mosquitoes with disrupted remating suppression mate with and produce offspring from multiple males, transferring dye to each. These data suggest that physical copulatory interactions occur independently of the female's receptivity to mate and that many of these interactions represent unsuccessful mating attempts that do not result in insemination.

Melanocortin 4 receptor signaling in Sim-1 neurons permits sexual receptivity in female mice

Female sexual dysfunction affects approximately 40% of women in the United States, yet few therapeutic options exist for these patients. The melanocortin system is a new treatment target for Hypoactive Sexual Desire Disorder (HSDD), but the neuronal pathways involved are unclear. In this study, female MC4R knockout mice lacking melanocortin 4 receptors (MC4Rs) paired with males were found to approach males less and have reduced receptivity to copulation, as indicated by a low lordosis quotient. The mice were then bred to express MC4Rs exclusively on Sim1 neurons (tbMC4RSim1 mice) or on oxytocin neurons (tbMC4ROxt mice). Lordosis behavior was normalized in tbMC4RSim1 mice and improved in tbMC4ROxt mice. In contrast, approach behavior was unchanged in tbMC4RSim1 mice but greatly increased in tbMC4ROxt animals. The changes were independent of melanocortin-driven metabolic effects. These results implicate MC4R signaling in Oxt neurons in appetitive behaviors and MC4R signaling in Sim1 neurons in female sexual receptivity, while suggesting melanocortin-driven sexual function does not rely on metabolic neural circuits. R01HD081792 This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Thermal phenotypic plasticity of pre- and post-copulatory male harm buffers sexual conflict in wild Drosophila melanogaster.

Strong sexual selection frequently leads to sexual conflict and ensuing male harm, whereby males increase their reproductive success at the expense of harming females. Male harm is a widespread evolutionary phenomenon with a strong bearing on population viability. Thus, understanding how it unfolds in the wild is a current priority. Here, we sampled a wild Drosophila melanogaster population and studied male harm across the normal range of temperatures under which it reproduces optimally in nature by comparing female lifetime reproductive success and underlying male harm mechanisms under monogamy (i.e. low male competition/harm) vs. polyandry (i.e. high male competition/harm). While females had equal lifetime reproductive success across temperatures under monogamy, polyandry resulted in a maximum decrease of female fitness at 24°C (35%), reducing its impact at both 20°C (22%), and 28°C (10%). Furthermore, female fitness components and pre- (i.e. harassment) and post-copulatory (i.e. ejaculate toxicity) mechanisms of male harm were asymmetrically affected by temperature. At 20°C, male harassment of females was reduced, and polyandry accelerated female actuarial aging. In contrast, the effect of mating on female receptivity (a component of ejaculate toxicity) was affected at 28°C, where the mating costs for females decreased and polyandry mostly resulted in accelerated reproductive aging. We thus show that, across a natural thermal range, sexual conflict processes and their effects on female fitness components are plastic and complex. As a result, the net effect of male harm on overall population viability is likely to be lower than previously surmised. We discuss how such plasticity may affect selection, adaptation and, ultimately, evolutionary rescue under a warming climate.

Double perinatal stress reduces the sexual response of adult female Wistar rats.

Early-life stress affects physiological development and produces changes in various aspects of emotional behavior. We sought to examine the effects of double perinatal stress (DPS)-a combination of prenatal systemic hypoxic-ischemic (HI) insults and repeated early maternal separation-on the estrus cycle and sexual behavior of adult rats. HI was induced by clamping the uterine arteries of pregnant rats for 45minutes on the 18th day of gestation (HI group). Sham control animals received laparotomy and anesthesia only. Pups were born at term. Maternal separation was performed from postnatal day 1 (P1) (P0 = day of birth) to P15. At P90, the sexual response of females in estrus was evaluated. Statistical analysis was performed using 2-way analysis of variance followed by Tukey's test. We considered the estrous cycle and sexual behavior of female rats submitted to DPS, as well as the influence of female behavior on the sexual response of male rats. Rats submitted to DPS showed a reduction in the lordosis quotient and in the lordosis rate, suggesting a reduction in female sexual receptivity. DPS female rats showed a reduction in the number of hops and darts and in the genital exploration time rate, suggesting a reduction in sexual proceptivity. In addition, males that interacted with DPS females showed a reduction in the number of ejaculations and in copulatory efficiency. Developing a deeper understanding of perinatal factors that affect adult female sexual response will allow for more effective interventions to prevent and treat such changes. On the other hand, the analysis of the sexual response allows assessing the quality of life and the general state of health. The development of animal models to investigate the environmental factors that interfere in the female sexual response may allow researchers to propose and test new therapeutic strategies. On the other hand, care must be exercised when interpreting animal data and extrapolating these results to estimate the possible effects of perinatal stressors on the human sexual response. Our results revealed that females subjected to DPS showed long-term effects on sexual behavior. In conclusion, managing stressors in prenatal life and early postnatal life can prevent problems in adult sexual life and improve overall health.

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

Female sexual dysfunction affects approximately 40% of women in the United States, yet few therapeutic options exist for these patients. The melanocortin system is a new treatment target for hypoactive sexual desire disorder (HSDD), but the neuronal pathways involved are unclear. In this study, the sexual behavior of female MC4R knockout mice lacking melanocortin 4 receptors (MC4Rs) was examined. The mice were then bred to express MC4Rs exclusively on Sim1 neurons (tbMC4RSim1 mice) or on oxytocin neurons (tbMC4ROxt mice) to examine the effect on sexual responsiveness. MC4R knockout mice were found to approach males less and have reduced receptivity to copulation, as indicated by a low lordosis quotient. These changes were independent of body weight. Lordosis behavior was normalized in tbMC4RSim1 mice and improved in tbMC4ROxt mice. In contrast, approach behavior was unchanged in tbMC4RSim1 mice but greatly increased in tbMC4ROxt animals. The changes were independent of melanocortin-driven metabolic effects. These results implicate MC4R signaling in Oxt neurons in appetitive behaviors and MC4R signaling in Sim1 neurons in female sexual receptivity, while suggesting melanocortin-driven sexual function does not rely on metabolic neural circuits.

Sexual motivation and performance in sexual naïve and experienced rats treated with ivermectin: an ultrasonic vocalization study

In mammals, ivermectin acts as a GABAA receptor agonist and stimulates GABA release. Previous studies showed that ivermectin (IVM) reduces sexual performance, impairing the latency to the first mount and intromission. These parameters are usually considered motivational parameters of sexual behavior. However, IVM increases GABAergic activity leading to motor incoordination. Thus, it is reasonable to propose that IVM affects sexual performance via motor incoordination pathways. The present study analyzed ultrasonic vocalization in rats to verify whether IVM impairs sexual behavior via motivational mechanisms or motor impairment. Because sexual experience attenuates the impairment of motor performance, rats with sexual experience were also studied. Sexually naive and experienced rats were administered a therapeutic IVM dose and saline. The rats were exposed to receptive females, and the latency to the first mount was evaluated, followed by the 50-kHz USV test. IVM treatment in naïve rats increased the latency to first to mount relative to Saline naïve rats, while no differences were observed between saline and experienced rats. In naïve-IVM rats, a reduced frequency and total calls and increased mean time of calls occur relative to SAL-naïve rats. Experienced IVM rats did not show differences in the frequency, mean, and maximal calls close to Saline experienced rats. However, an increase in the total calls and the dominant frequency of calls were observed in IVM-experienced rats compared to Saline experienced rats. A negative and positive correlation occurred between the latency to the first mount and USVs in groups with and without ivermectin exposure. Hence, we propose that ivermectin increased the sexual motivation of rats exposed to a female in estrous based in USVs despite an increased latency to the first mount that occurred. The increased latency to the first mount resulted from motor incoordination, as previously observed and proposed by our group.

How big is a beaked whale? A review of body length and sexual size dimorphism in the family Ziphiidae

There is a paucity of data on the family Ziphiidae (the beaked whales) and even basic information, such as body length, is not available for some species. This review examines published records of body length for 20 of the 21 currently recognised species of beaked whale. It considers maximum, median and modal body lengths, where possible by sex. For Cuvier’s, Blainville’s and Gray’s beaked whales, modal and median lengths were much shorter than the maximum reported lengths; this may reflect misidentification of the largest animals. Although males of some species reached a greater maximum size, there was only a significant difference in median body length for three species: True’s beaked whale; the strap-toothed whale; and Gervais’ beaked whale. In all three cases, females had a significantly larger median length. The apparent lack of consistent sexual dimorphism in body length suggests that, while male beaked whales use their tusks as weapons to compete aggressively for access to receptive females, large size does not give a competitive advantage. This may be a result of the way the sexually dimorphic tusks are used during combat. The only exception to this rule appears to be the northern bottlenose whale, for which males consistently reach greater body lengths than the largest females. Male-male combat appears to take a different form in this species.