Receptive Females Research Articles

Female Phalangium opilio use fellatio to compensate sexual avoidance

Sexual conflict arises from differences in reproductive interests between the sexes. We allowed the female harvestman Phalangium opilio to sequentially mate with two different males to examine female sexual receptivity in this species. Virgin females were more sexually receptive than non-virgins. Males exhibited a high interest in repeated copulations with the same female, often engaging in aggressive behaviours such as biting and reversed sexual cannibalism. Fellatio, a behaviour in which females lick the male’s penis, was observed in 44% of trials and was associated with female unwillingness to mate and shorter copulation duration. Fellatio was repeatable, suggesting that it is influenced by individual characteristics or underlying physiological factors. Female lifespan was negatively correlated with the total number of eggs produced, suggesting a trade-off between reproduction and longevity. These findings provide evidence of the appearance of fellatio, a female mating strategy that evolved as compensation of avoiding unwanted sexual intercourse.

Hybrid grain production in wheat benefits from synchronized flowering and high female flower receptivity.

The performance of plant hybrids relative to line breeding types is generally associated with higher yields, better adaptation, and improved yield stability. In bread wheat (Triticum aestivum L.), however, a broad commercial success for hybrids has not been accomplished until now largely due to the low efficiency of hybrid grain production, which is highly attributable to its self-pollinating nature. To better understand how hybrid wheat grains can be produced more effectively, we investigated the influence of synchronized flowering between female, i.e. male-sterile, lines and their male cross-pollinator lines as well as of the duration of flowering on hybrid grain production. We found that synchronization of flowering in combination with the longest possible temporal overlap had the largest positive effect on hybrid grain production. However, despite sufficient spatial and temporal synchronization of flowering, we also found that some female lines had lower hybrid grain set than others, suggesting genetic differences in female floral receptivity. To better assess female receptivity, we established a new phenotyping scale of male-sterile wheat flowers that provides the floral basics for effective cross-pollination. Applying this scale in our field and greenhouse trials revealed that better performing female lines remained longer in the pollen-receptive phase.

Spermatogenic and Libido Enhancing Effect of Ethanol Extract of Kigelia Africana in ∆9 Tetrahydrocannabinol Induced Erectile Dysfunction in Male Wistar Rats

Erectile dysfunction has remained one of the major global health issues for the past two decades. Since the discovery of phosphodiesterase type 5 inhibitors, a significant number of patients have solved the issue of erectile dysfunction. However, the wide distribution of phosphodiesterase type 5 enzymes at various sites of the body led phosphodiesterase type 5 inhibitors to cause various unnecessary outcomes. Hence, it is vital to look for optional agents that could solve these limitations. In this present work, erectile dysfunction was induced by administering 30 mg/kgbwt THC for 3 days. Treatment given was as follows: A - Normal Control, B - Std control (THC+Viagra), C - Negative control (THC only), D - THC + 200 mg/Kgbwt ethanol leaf extract of Kigelia africana (200 mg/Kgbwt), E - THC + 400 mg/Kgbwt ethanol leaf extract of Kigelia africana for a succession of 14 days. Sexual behaviour parameters were monitored in the male rats on Days 1, 7 and 14 respectively after administration by pairing with a receptive female (1:1); thereafter, rats were sacrificed and serum was collected for some biochemical parameters using standard method. Cage side observation on the animals revealed prospective behaviours by the receptive female rats and precopulatory behaviours by the ethanol extract K.africana treated male rats.The extract at 200 and 400 mg/kg body weight significantly (P<0.05) increased the frequencies of mount and intromission.In addition, the ejaculation latency was significantly (P< 0.05) prolonged.The latencies of mount and intromission were reduced significantly (P<0.05) whereas ejaculation frequency increased. The extract also reduced the post-ejaculatory interval of the Wistar rats. Computed percentages of index of libido, mounted, intromitted, ejaculated and copulatory efficiency were significantly (p<0.05) higher in the extract-treated animals in a dosage dependent manner than the control whereas the inter copulatory interval decreased significantly. The extract also significantly (p<0.05) increased the serum testosterone, FSH and LH concentration but significantly (p<0.05) reduced serum oestrogen, prolactin and progesterone of the treated groups when compared with the control. The extract also significantly (p<0.05) increased the sperm motility, total sperm count, and sperm viability but produced a significant (p<0.05) decrease in serum immobility when compared with the THC control. It can be inferred from this work that an extract of K. africana may elicit spermatogenic, androgenic and libido enhancing activities in THC induced erectile dysfunction in a dosage dependent manner.

Variation in thermal courtship activity curves across individuals exceeds variation across populations and sexes.

The dynamics of mating interactions can vary in response to a wide variety of environmental factors. Here, we investigate the potential for individuals to vary consistently in the environmental conditions under which they actively engage in courtship. Specifically, we quantify variation in how courtship activity changes with environmental temperature across levels of biological organization in Enchenopa binotata treehoppers. Male E. binotata produce vibrational courtship signals and receptive females respond with their own sex-specific vibrational courtship signal. We tested each individual twice for the production of courtship signals across a range of ecologically-relevant temperatures (18 - 36 °C). Then, we measured repeatability and variability in the resulting thermal courtship activity curves, including the temperature of peak activity and tolerance to thermal extremes. We also looked at patterns of variation across populations and sexes. We found minimal variation across populations, but significant variation across individuals. Specifically, we found prevalent repeatability in how thermally generalized or specialized individuals are. However, repeatability was limited to females only. We also found higher variability in female traits than in male traits, although patterns of variability did not always predict patterns of repeatability. These results suggest that thermal variation could alter the dynamics of mate competition, and that-due to potentially different selective optima for males and females-the sexes may respond to changes in temperature in different ways. Specifically, females show a higher potential to adapt but males show a higher potential to be more robust to changes in temperature due to overall higher courtship activity across temperatures.

Males discriminate between substrate-borne cues of conspecific females based on age and mating status in the jumping spider, Habronattus brunneus.

Sexual selection is often studied with a focus on female mate choice, wherein females evaluate male signals to select an optimal mate. However, in some systems, males should also make careful decisions about the females they choose to court, particularly when faced with the risk of precopulatory sexual cannibalism. Here, we explore the idea that male jumping spiders (Habronattus brunneus) may mitigate this risk by responding to female cues probably associated with female aggression and/or receptivity. We tested mature male spiders' ability to discriminate between substrate-borne cues (i.e. silk and excreta) produced by conspecific females of different ages and mating statuses. We found that males spent more time exploring cues produced by mature, non-mated females compared with either immature females or mated females. Heightened interest in cues produced by females that are sexually mature but not yet mated may allow males to reduce cannibalism risk, reduce wasted courtship effort and increase their reproductive success. The use of chemical and/or tactile cues in jumping spider courtship behaviour has been vastly understudied compared with the ways they use vision; this study provides the groundwork for understanding how these sensory modalities interact.

Mating receptivity mediated by endosymbiont interactions in a haplodiploid thrips species.

Many arthropods carry maternally inherited endosymbionts that cause cytoplasmic incompatibility (CI), manifested as embryonic mortality in matings of infected males with uninfected females. Infected females, however, do not suffer this cost. Therefore, in populations with mixed endosymbiont infections, selection is expected to favour mechanisms that enable hosts to avoid or mitigate CI. This may include changes in mating behaviour, such as reduced female receptivity to mating and/or remating when approached by incompatible males. Here, we investigated mating behavioural traits in haplodiploid thrips naturally associated with two CI-inducing endosymbionts, Cardinium and Wolbachia. Compared with females with both endosymbionts, those with only Cardinium showed reduced receptivity to males carrying both. However, surprisingly, females without endosymbionts were not less receptive to incompatible males. Furthermore, in contrast to females without endosymbionts, females with Cardinium were far less likely to remate with incompatible than compatible males irrespective of the compatibility type of the first mating. Our results suggest that endosymbiont-specific sexual selection processes occur, whereby females carrying only Cardinium recognize Wolbachia in coinfected males to avoid CI. This may hinder a CI-driven Wolbachia spread. Endosymbiont-mediated mating behaviours may be crucial for the dynamics of CI-inducing endosymbionts and their application in pest management strategies.

Effects of double neonatal stress on female rat sexual behaviour

Neonatal stress affects psychological and physiological development and may be associated with affective disorders. The aim was to examine the effects of double neonatal stress (DNS) – a combination of limited bedding and nesting (LBN) and repeated maternal separation (MS) – on the oestrous cycle and sexual behaviour of adult female rats. LBN was achieved by removing part of the wood shavings from the boxes. In the control group, each box was lined with 100 g of wood shavings, while in the experimental group there were only 10 g of wood shavings. MS was performed from P1 (P0 = day of birth) to P15. At P90, the sexual response of females in oestrus was evaluated. Statistical analysis was performed using two-way analysis of variance followed by Tukey's test. The size and profile of the oestrous cycle and the sexual behaviour of female rats submitted to the DNS were considered, as well as the influence of female behaviour on the sexual response of male rats. Female rats submitted to DNS showed a reduction in the lordosis quotient, suggesting a reduction in female receptivity. These rats also showed a reduction in the number of hops and darts, the number of ear wiggles, and the genital exploration time rate, suggesting a reduction in proceptivity. The males that interacted with the females of the DNS group showed a reduction in intromission ratio. Experimental model that mimics neonatal factors that affect adult female sexual response will allow more effective interventions to prevent and treat such changes. In addition, analysis of the female sexual response makes it possible to assess the general state of health and quality of life. In female rats, DNS exerted inhibitory effects on sexual behaviour. LBN was probably the most important factor. In conclusion, combating childhood poverty can be a key measure to prevent problems in the sex life of adults and improve overall health.

Male cuticular pheromones stimulate removal of the mating plug and promote re-mating through pC1 neurons in Drosophila females

In birds and insects, the female uptakes sperm for a specific duration post-copulation known as the ejaculate holding period (EHP) before expelling unused sperm and the mating plug through sperm ejection. In this study, we found that Drosophila melanogaster females shortens the EHP when incubated with males or mated females shortly after the first mating. This phenomenon, which we termed male-induced EHP shortening (MIES), requires Or47b+ olfactory and ppk23+ gustatory neurons, activated by 2-methyltetracosane and 7-tricosene, respectively. These odorants raise cAMP levels in pC1 neurons, responsible for processing male courtship cues and regulating female mating receptivity. Elevated cAMP levels in pC1 neurons reduce EHP and reinstate their responsiveness to male courtship cues, promoting re-mating with faster sperm ejection. This study established MIES as a genetically tractable model of sexual plasticity with a conserved neural mechanism.

Male cuticular pheromones stimulate removal of the mating plug and promote re-mating through pC1 neurons in Drosophila females.

In birds and insects, the female uptakes sperm for a specific duration post-copulation known as the ejaculate holding period (EHP) before expelling unused sperm and the mating plug through sperm ejection. In this study, we found that Drosophila melanogaster females shortens the EHP when incubated with males or mated females shortly after the first mating. This phenomenon, which we termed male-induced EHP shortening (MIES), requires Or47b+ olfactory and ppk23+ gustatory neurons, activated by 2-methyltetracosane and 7-tricosene, respectively. These odorants raise cAMP levels in pC1 neurons, responsible for processing male courtship cues and regulating female mating receptivity. Elevated cAMP levels in pC1 neurons reduce EHP and reinstate their responsiveness to male courtship cues, promoting re-mating with faster sperm ejection. This study established MIES as a genetically tractable model of sexual plasticity with a conserved neural mechanism.

The function of juvenile-adult transition axis in female sexual receptivity of Drosophila melanogaster.

Female sexual receptivity is essential for reproduction of a species. Neuropeptides play the main role in regulating female receptivity. However, whether neuropeptides regulate female sexual receptivity during the neurodevelopment is unknown. Here, we found the peptide hormone prothoracicotropic hormone (PTTH), which belongs to the insect PG (prothoracic gland) axis, negatively regulated virgin female receptivity through ecdysone during neurodevelopment in Drosophila melanogaster. We identified PTTH neurons as doublesex-positive neurons, they regulated virgin female receptivity before the metamorphosis during the third-instar larval stage. PTTH deletion resulted in the increased EcR-A expression in the whole newly formed prepupae. Furthermore, the ecdysone receptor EcR-A in pC1 neurons positively regulated virgin female receptivity during metamorphosis. The decreased EcR-A in pC1 neurons induced abnormal morphological development of pC1 neurons without changing neural activity. Among all subtypes of pC1 neurons, the function of EcR-A in pC1b neurons was necessary for virgin female copulation rate. These suggested that the changes of synaptic connections between pC1b and other neurons decreased female copulation rate. Moreover, female receptivity significantly decreased when the expression of PTTH receptor Torso was reduced in pC1 neurons. This suggested that PTTH not only regulates female receptivity through ecdysone but also through affecting female receptivity associated neurons directly. The PG axis has similar functional strategy as the hypothalamic-pituitary-gonadal axis in mammals to trigger the juvenile-adult transition. Our work suggests a general mechanism underlying which the neurodevelopment during maturation regulates female sexual receptivity.

Nephila spider male aggregation: preference for optimal female size and web clustering.

Sexual size dimorphism theory predicts biased operational sex ratios (OSRs) and an uneven distribution of males among certain females. We studied this phenomenon through a field census of the giant wood spider Nephila pilipes (family Nephilidae) in Singapore, a species where females are, on average, 6.9 times larger than males. Specifically, we tested two hypotheses concerning male distribution, given their tendency to aggregate in certain female webs. The optimal female size hypothesis predicts that males would predominantly occupy webs of intermediate-sized females. The web clustering hypothesis posits that more males would be found in webs closer together compared to those farther apart. Our snapshot census revealed a female-biased OSR (females: males = 1.85) with an uneven distribution of males in female webs. Most males were found in webs of intermediate-sized females aligning with the optimal female size hypothesis. Proximity among female webs was indicative of male presence, lending support to the web clustering hypothesis. While our study's limited sample size warrants caution, we conclude that in N. pilipes, male occupation of female webs is facilitated by the clustering of webs, and males prefer to cohabit with optimally sized, receptive females.

Male consort behavior is driven by female mate choice and receptive synchrony in Tibetan macaques (Macaca thibetana)

In group-living animals, males’ fighting abilities were usually mediated via dominance rank to sort males into a queue to access fertile females, especially in non-human primates. However, the correlation between male reproductive success and consortship, an alternative high-ranking male reproductive strategy, varies across species, obscuring the adaptive significance of male consort behavior. The priority of access (PoA) model is commonly used to predict male mating/reproductive success based on male dominance rank and female reproductive synchrony. In this study, we aimed to assess the applicability of the PoA model in predicting the distribution of male mating success and consortship, while also identifying the main factors influencing these outcomes in a group of free-ranging Tibetan macaques (Macaca thibetana) at Huangshan, China. Our results showed that (1) the male mating was significantly skewed towards the highest-ranking males, deviating from the expectations set by the PoA model. This departure was attributed to both female mate choice and male consort behavior. Notably, the influence of male rank on mating success decreased as the number of receptive females increased. Additionally, female mate choice became less significant when consorted by males compared to situations when they were not consorted; (2) the observed consort behavior among males was lower than what the PoA model predicted for available receptive days, while high-ranking males exhibited a gradual increase in their consort behavior with the rising number of receptive females. Our results suggests that, in Tibetan macaques, male consort behavior imposed limitations on female mate choice, and mitigated the impact of male dominance rank on male mating success as the number of receptive females grew. We propose that male consort behavior could be driven by female counter-monopoly strategies, and the simultaneous occurrence of consort behavior and opportunistic mating may represent the most effective mating tactic in this promiscuous mating system.

The function of prolonged copulations in Enchenopa treehoppers (Hemiptera: Membracidae).

Copulations are very brief in many species, sometimes taking only seconds, but in other species, they can be quite prolonged. Potential explanations for prolonged copulations include time requirements for the transfer of sperm and/or other ejaculate substances. Ejaculate substances could function to regulate female receptivity to subsequent matings, provide nutritional nuptial gifts, or hasten egg oviposition at a potential survival cost to the female. We investigated prolonged copulation in a member of the Enchenopa binotata complex of treehoppers (Hemiptera: Membracidae), in which females rarely remate and copulation can last several hours. We assigned females to treatments in which we interrupted copulation at different times. We also included a control where copulation was not interrupted. We found that females that experienced shorter copulations were more likely to be subsequently receptive to an attractive male. We also found that few females produced offspring when they engaged in short copulations compared to those with longer copulations. We did not find any differences in female survival. Our results support the sperm transfer and receptivity regulation hypotheses. We discuss potential reasons for why these processes should take so long in a species with low female remating.

The use of anthropogenic areas helps explain male brown bear movement rates and distance travelled during the mating season

AbstractDuring the reproductive period, mating strategies are a significant driver of adaptations in animal behaviour. For instance, for polygamous species, greater movement rates during the mating season may be advantageous due to the increased probability of encountering several potential mates. The brown bear Ursus arctos is a solitary carnivore that lives at low densities, with a polygamous mating system and an extended mating season of nearly 3 months. Here, we hypothesized that male brown bears may show changes in movement patterns and space‐use behaviour during their mating season. Using long‐term (2002–2013) telemetry data from the Finnish Karelia male population (n = 24 individuals; n = 10 688 GPS locations), we first analysed daily movement metrics, that is, speed, net and total distance with respect to the period (mating vs. post‐mating) and several environmental predictors. Then, we conducted a step‐selection analysis for each of these periods. Throughout the year, male bears selected forested/shrub habitats and increased movement rates near main roads. During the mating season, reproductive needs seem to trigger roaming behaviour in adult males to maximize encounter rates with potential receptive females. However, all movement metrics increased within areas of high human activity, suggesting a bear response to a higher risk perception while using those areas. During the post‐mating period, overlapping with the bear hyperphagia and the hunting season, males selected anthropogenic areas farther from main roads and trails, suggesting a trade‐off between foraging opportunities and risk avoidance.

UHPLC-MS/MS profiling and in vivo aphrodisiac and androgenic effects of the aqueous extract of the roots of Schumanniophyton magnificum (K. Schum.) Harms

Ethnopharmacological relevanceSchumanniophyton magnificum is a medicinal plant used to manage many ailments including malaria, skin diseases, parasitic infections, male sexual dysfunctions, female infertility and typhoid fever. However, no scientific investigation has been made for its folkloric use by the “Baka” Pygmies of Cameroon as an aphrodisiac. Aim of the studyTo investigate the aphrodisiac and androgenic activities of the aqueous extract of the roots of Schumanniophyton magnificum in male rats and analyze the phytoconstituents by UHPLC/MS. Materials and methodsTwenty-five male rats of 16-weeks old were divided into 5 groups and orally treated for 30 days with distilled water (10 ml/kg), or sildenafil citrate (5 mg/kg), or the aqueous extract of Schumanniophyton magnificum (43 mg/kg, 86 mg/kg and 172 mg/kg). The sexual behaviour parameters were monitored on day 1 and 30 by pairing male rats to receptive females. At the end of the experiment, rats were killed and the blood and reproductive organs were collected for histological sectioning, sperm analysis and biochemical analysis. The presence of phytoconstituents and their structures were revealed by UHPLC/MS. ResultsThe plant extract significantly increased the mount, ejaculation and intromission frequencies in comparison to those in the normal control group; and significantly doubled the serum testosterone levels (2.15 ± 0.70 ng/ml) compared to the normal control group. UHPLC/MS of the aqueous extract of Schumanniophyton magnificum identified 7 major compounds such as Schumanniofioside A, Noreugenin and Rohitukine, with antioxidant and antibacterial activities. The plant extracts significantly increased the penile nitric oxide levels (P <0.05). These results were similar to those obtained after administration of sildenafil citrate. ConclusionsThe aqueous extract of Schumanniophyton magnificum could be an alternative for erectile dysfunction management.

A simple method for repeated in vivo sperm collection from laboratory mice

PurposeMouse spermatozoa for archiving laboratory mice or for in vitro fertilization (IVF) are routinely obtained from the cauda epididymis of adult males sacrificed for this purpose. To avoid the death of the donor, we tested whether a precisely timed interruption of the mating act could be used for repeated sperm collection from laboratory mice.MethodsSperm donors (B6D2F1) were mated with a receptive female, and mating behavior was observed. The stud was separated from the female 1–2 s after the onset of the ejaculatory shudder. The ejected copulatory plug with the yellowish viscous ejaculate was carefully removed from the penile cup.ResultsA total of 80 ejaculates were successfully obtained from 100 ejaculations. The latency to first mount was 1.1 ± 1.1 min (mean ± SD) and to ejaculation 8.1 ± 4.7 min. The average number of mounts to ejaculation was 10.5 ± 5.8, and the mean number of spermatozoa per collected ejaculate was 1.86 ± 1.05 × 106. An average fertilization rate of 76% was observed after IVF.ConclusionsSeparating the stud from the female just before ejaculation is feasible, easy to learn, and requires no special equipment. The sperm count of collected ejaculates is lower than natural ejaculations, but higher than previous in vivo sperm collection methods achieved. We recommend this simple sperm collection method in mice, especially when the donor cannot be sacrificed and/or repeated sperm collection from the same animal is required for experimental purposes.

Aqueous extract of Pycnanthus angolensis (Welw.) Warb. (Myristicaceae) alleviates paroxetine-induced erectile dysfunction in male rats

Background: Erectile dysfunction is the inability to achieve and maintain an adequate erection for sexual performance. Pycnanthus angolensis (Welw.) Warb. is a medicinal plant used by the traditional healers of the Southern region of Cameroon to manage male infertility and especially erectile dysfunction. Aim and objectives: This study aimed at investigating the effects of aqueous extract of Pycnanthus angolensis wood were investigated on paroxetine-induced erectile dysfunction in male rats. Material and methods: Thirty Wistar albino male rats (160-180 g) were randomly distributed into six groups of five animals each. Erectile dysfunction was induced in 5 groups for 21 days by oral administration of paroxetine (10 mg/kg), once a day. After induction, rats were orally treated during 14 days with three doses of plant extract (43, 86 and 172 mg/kg) except 2 groups which were given distilled water and sildenafil (5 mg/kg), respectively. Sexual behaviors were monitored on days 1, 4, 7, and 14 by pairing male rats to receptive females. After 14 days- treatment, the rats were killed by decapitation under ether anesthesia. The reproductive organs were collected for histological and biochemical analysis. Results: Paroxetine induced erectile dysfunction characterized by a significant decrease (p&lt;0.05) in sexual arousal and performance of male rats. Nevertheless, this erectile dysfunction was improved by administration of the aqueous extract of Pycnanthus angolensis at the different doses. The administration of paroxetine significantly (p&lt;0.05) reduced the nitric oxide level by 66.67% when compared to the distilled water-group. After 14 days-treatment, the extract induced significant increases (p&lt;0.05) in the sexual performance parameters (mounts, intromissions and ejaculations frequency) as well as in the sexual arousal of the male rats. Results were markedly pronounced with the plant extract at the doses of 86 and 172 mg/kg. The nitric oxide levels in the erectile dysfunction-induced rats with paroxetine were restored after treatment with the plant extract. The degenerated seminiferous tubules and the low density of spermatozoa observed in the histological sections of the erectile dysfunction-induced rats with paroxetine, were restored after treatments with sildenafil and the aqueous extract at either doses (43, 86 and 172 mg/kg). Conclusions: Aqueous extract of Pycnanthus angolensis (Welw.) Warb alleviated the paroxetine-related erectile dysfunction by enhancing sexual behavior and the production of nitric oxide. In view of the abovementioned results, Pycnanthus angolensis (Welw.) Warb could be considered as an alternative treatment in the erection dysfunction management.

Krause corpuscles are genital vibrotactile sensors for sexual behaviours

Krause corpuscles, which were discovered in the 1850s, are specialized sensory structures found within the genitalia and other mucocutaneous tissues1–4. The physiological properties and functions of Krause corpuscles have remained unclear since their discovery. Here we report the anatomical and physiological properties of Krause corpuscles of the mouse clitoris and penis and their roles in sexual behaviour. We observed a high density of Krause corpuscles in the clitoris compared with the penis. Using mouse genetic tools, we identified two distinct somatosensory neuron subtypes that innervate Krause corpuscles of both the clitoris and penis and project to a unique sensory terminal region of the spinal cord. In vivo electrophysiology and calcium imaging experiments showed that both Krause corpuscle afferent types are A-fibre rapid-adapting low-threshold mechanoreceptors, optimally tuned to dynamic, light-touch and mechanical vibrations (40–80 Hz) applied to the clitoris or penis. Functionally, selective optogenetic activation of Krause corpuscle afferent terminals evoked penile erection in male mice and vaginal contraction in female mice, while genetic ablation of Krause corpuscles impaired intromission and ejaculation of males and reduced sexual receptivity of females. Thus, Krause corpuscles of the clitoris and penis are highly sensitive mechanical vibration detectors that mediate sexually dimorphic mating behaviours.

Acute ethanol disrupts conditioned inhibition in the male rat.

Alcohol can disrupt conditioned sexual inhibition (CSI) established by first-order conditioning in male rats. CSI can also be induced using second-order conditioning, during which male rats are trained to associate a neutral odor with a nonreceptive female. As a result, when given access to two receptive females (one scented and one unscented) during a copulatory preference test, they display CSI toward the scented female. The present study examined the effect of low-to-moderate doses of alcohol on CSI and brain activation following exposure to alcohol and the olfactory cue alone. Sexually-naïve Long-Evans rats received alternate conditioning sessions with unscented receptive or scented (almond extract) non-receptive females. Following the conditioning phase, males were injected with saline, alcohol 0.5g/kg or 1g/kg, 45min before a copulatory test with two receptive females, with one bearing the olfactory cue. Fos activation was later assessed, following exposure to alcohol and the olfactory cue alone, in several brain regions involved in the expression and regulation of male sexual behavior. While males in the saline group displayed sexual avoidance towards the scented female, those injected with alcohol before the copulatory test, regardless of the dose, copulated indiscriminately with both females. Subsequent exposure to alcohol and the olfactory cue alone induced different Fos expression between groups in several brain regions. Low to moderate doses of alcohol disrupt conditioned sexual inhibition in male rats and induce a differential pattern of neural activation, particularly in regions involved in the expression and regulation of sexual behavior.

Comparative analysis of intragroup intermale relationships: a study of wild bonobos (Pan paniscus) in Wamba, Democratic Republic of Congo and chimpanzees (Pan troglodytes) in Kalinzu Forest Reserve, Uganda.

Although chimpanzees (Pan troglodytes) and bonobos (Pan paniscus) share a multi-male/multi-female societal organization and form male-philopatric groups, disparities in terms of male aggression and stability of temporary parties are thought to exist among them. However, existing research in bonobos has mainly focused on the high social status, prolonged receptivity, and characteristic sexual behaviors of females, leaving the behaviors of males understudied. Moreover, prior comparative studies on Pan suffer from methodological inconsistencies. This study addresses these gaps by employing a uniform observation method to explore party attendance and aggressive interactions among male bonobos in Wamba and male chimpanzees in Kalinzu. Unlike male chimpanzees, which exhibit dispersion in the absence of receptive females in the group, male bonobos showed a lesser degree of such dispersion. Although the overall frequency of aggressive interactions per observation unit did not significantly differ between the two species, the nature of these interactions varied. Notably, severe aggressive behaviors such as physical confrontations among adult males were absent in bonobos, with most aggression occurring between the sons of the two highest-ranking females. Additionally, in bonobos, females actively engaged in polyadic aggressive behavior as aggressors, while all instances of coalitionary aggression in chimpanzees originated from male aggressors. These findings underscore the substantial impact of female behaviors on the observed distinctions in male aggressive interactions between the two species.