Alterations to the copulatory sequence in young adult male Sprague-Dawley rats administered a ketogenic diet.

Ketogenic diets (KDs) have shown therapeutic potential for a range of neuropsychiatric disorders; however, there is insufficient data regarding the behavioral impacts of KDs in healthy populations. Here, we examined the impact of a KD on sexual behavior in young adult male Sprague-Dawley rats maintained on either a KD or standard chow diet (SD). We found that KD males exhibited higher mount rates, higher intromission rates (third and fourth tests only), and lower ejaculation likelihood (second test only) compared to SD males. Consequently, it may be that experience-dependent changes in the processing of sexual stimuli are not occurring as efficiently in KD males, thereby yielding the observed copulatory sequence alterations.

Metabolic pathways that mediate the effects of food deprivation on reproductive behavior in female Drosophila melanogaster.

In most species studied, energy deficits inhibit female reproductive behavior, but the location and nature of energy sensors and how they affect behavior are unknown. Progress has been facilitated by using Drosophila melanogaster, a species in which reproduction and food availability are closely linked. Adult males and females were either fed or food deprived (FD) and then tested in an arena with a fed, opposite-sex conspecific with no food in the testing arena. Only FD females (not FD males) significantly decreased their copulation rate and increased their copulation latency, and the effects of FD were prevented in females fed either yeast alone or glucose alone, but not sucralose alone, cholesterol alone, or amino acids alone. It is well-known that high-fat diets inhibit copulation rate in this species, and the effects of FD on copulation rate were mimicked by treatment with an inhibitor of glucose but not free fatty acid oxidation. The availability of oxidizable glucose was a necessary condition for copulation rate in females fed either yeast alone or fed a nutritive fly medium, which suggests that the critical component of yeast for female copulation rate is oxidizable glucose. Thus, female copulation rate in D. melanogaster is sensitive to the availability of oxidizable metabolic fuels, particularly the availability of oxidizable glucose or substrates/byproducts of glycolysis.NEW & NOTEWORTHY Copulation rate was decreased in food-deprived female but not in male adults when tested without food in the testing arena. Copulation rate was 1) maintained by feeding glucose alone, yeast alone, nutritive medium lacking yeast, but not sucralose, amino acids, or cholesterol alone; 2) decreased by inhibition of glycolysis in females fed either nutritive medium or yeast alone; and 3) not affected by inhibition of fatty acid oxidation. Thus, female copulation rate was linked to glycolytic status.

Copulation Duration and Sperm Precedence with Reference to Larval Diapause Induction in Monochamus alternatus Hope (Coleoptera: Cerambycidae).

Adults of the pine sawyer Monochamus alternatus are the primary vector of Bursaphelenchus xylophilus, the causative agent of pine wilt disease. A sawyer subspecies in Taiwan (abbreviated 'T') has two generations a year (bivoltinism) due to facultative diapause, whereas another subspecies in Japan (abbreviated 'J') has a one- or two-year life cycle due to obligate diapause. T, with two infection periods a year, will cause more severe disease epidemics than J if it is introduced into Japan. Inter-subspecies hybridization may inhibit the expression of bivoltinism because many F1 hybrids induce diapause. To predict the effects of introducing T into Japan, the present study investigated copulation duration and late-male sperm precedence to fertilize eggs. The results indicated that a single copulation for more than 65 s supplied sufficient sperm to fertilize a lifetime production of eggs. The incidence of larval diapause was 0.15 for the offspring of T females that mated with a T male and increased to 0.292-0.333 after remating with a J male, while the incidence of larval diapause was 0.900-1.000 for hybrids from T females mated with a J male. Consequently, the estimated proportion of second-male sperm used by T females was 0.185-0.217. The effects of introducing T populations into Japan on the severity of disease epidemics were also discussed.

Factors Influencing Copulation Duration in Dastarcus helophoroides (Fairmaire) (Coleoptera: Bothrideridae).

The gregarious ectoparasitic beetle Dastarcus helophoroides (Fairmaire) is considered a primary biocontrol agent for controlling several cerambycid pests in East Asian countries. A thorough study of reproductive behavior is a prerequisite for the mass production of natural insect predators. Nonetheless, little attention has been given to this ectoparasitic beetle. We performed a series of trials to assess whether the adult copulation duration, a key behavioral trait, is differentially influenced by physiological and ecological factors, including body size, mating history, kinship, sex ratio, mating sequence, feeding status, ambient temperature, photoperiod, and time of day. Additionally, the effect of the copulation duration on the reproductive output of this beetle was also investigated. The results indicated that the copulation duration varied considerably, ranging from 1.12 min to 16.40 min and lasting for an average of 9.11 ± 0.12 min. Females with longer copulations laid more eggs and had a greater proportion of eggs hatched. Medium-sized individuals copulated significantly longer than small- and large-sized individuals. The copulation durations were significantly longer when both sexes experienced an asymmetric mating history than when both sexes experienced a symmetric mating history. Inbred couples copulated significantly longer than outbred couples. In terms of the adult sex ratio, increasing the density of females (polygamous group) or males (polyandrous group) led to significantly longer copulation durations than those in the monogamous group. The copulation durations gradually decreased with increasing the mating sequence and temperature. Food-absence couples copulated significantly longer than food-presence couples. The mean copulation duration of the scotophase was significantly longer than that of the photophase. These results demonstrate that all of the analyzed factors emerge as important factors influencing the copulation duration, ultimately affecting the reproductive outputs in this ectoparasitic beetle.

Sniffing behavior of semi free-ranging Barbary macaques (Macaca sylvanus).

Olfaction is one of the evolutionarily oldest senses and plays a fundamental role in foraging and social interactions across mammals. In primates, the role of olfaction is now well recognized, but better investigated in strepsirrhine and platyrrhine primates than in catarrhines. We observed the sniffing behavior of semi-free ranging Barbary macaques, Macaca sylvanus, at Affenberg Salem, Germany, to assess how frequently macaques sniff and in which contexts, and how sniffing is affected by sex and age. Focal observations of 24 males and 24 females aged 1-25 years showed that Barbary macaques sniffed, on average, 5.24 times per hour, with more than 80% of sniffs directed at food. Irrespective of the context, younger individuals sniffed more often than older ones. Females' sniffs were more often directed at food than male sniffs, while males sniffed more often than females in a social context. Sniffs at conspecifics occurred primarily in a sexual context, with 70% of social sniffs directed at female anogenital swellings performed by males. Of the observed 176 anogenital inspections, 51 involved sniffing of the swelling. Olfactory inspections were followed by copulation significantly less often than merely visual inspections, suggesting that anogenital odors may play a role in male mating decisions, but the role of olfaction in sexual interactions warrants further investigations. In sum, results show that Barbary macaques routinely use olfaction during feeding, but also in a socio-sexual context, corroborating the relevance of the olfactory sense in the lives of catarrhine primates.

Replenishment of Drosophila Male Pheromone After Mating.

Insect exocrine gland products can be involved in sexual communication, defense, territory labelling, aggregation and alarm. In the vinegar fly Drosophila melanogaster the ejaculatory bulb synthesizes and releases 11-cis-Vaccenyl acetate (cVa). This pheromone, transferred to the female during copulation, affects aggregation, courtship and male-male aggressive behaviors. To determine the ability of male flies to replenish their cVa levels, males of a control laboratory strain and from the desat1 pheromone-defective mutant strain were allowed to mate successively with several females. We measured mating frequency, duration and latency, the amount of cVa transferred to mated females and the residual cVa in tested males. Mating duration remained constant with multiple matings, but we found that the amount of cVa transferred to females declined with multiple matings, indicating that, over short, biologically-relevant periods, replenishment of the pheromone does not keep up with mating frequency, resulting in the transfer of varying quantities of cVa. Adult responses to cVa are affected by early developmental exposure to this pheromone; our revelation of quantitative variation in the amount of cVa transferred to females in the event of multiple matings by a male suggests variable responses to cVa shown by adults produced by such matings. This implies that the natural role of this compound may be richer than suggested by laboratory experiments that study only one mating event and its immediate behavioral or neurobiological consequences.

Copulation of Ixodes ricinus males and females on the host and its potential impact on pathogen transmission.

INTRODUCTION AND OBJECTIVE: The common tick Ixodes ricinus is one of Europe's most important vectors of tick-borne diseases. The increased risk of attacks by this tick suggests the need for identification of factors contributing to the transmission of tick-borne pathogens, and the routes of pathogen circulation in nature. MATERIAL AND METHODS: Polymerase chain reaction was used to investigate the prevalence of four pathogens, i.e. Borrelia burgdorferi s.l. (Bb), Anaplasma phagocytophilum (Ap), Babesia spp. (Bs), and Bartonella spp. (Ba) in I. ricinus females and males mating on dogs in south-central Poland. RESULTS: The study revealed the presence of three pathogens: Bb, Ap, and Bs in 9.4%, 5.4%, and 5.4% of all I. ricinus adults in copula, respectively. Co-infection with two pathogens was detected in one tick specimen. Borrelia burgdorferi spirochetes were isolated in two females and two males in copula, but the sexual transfer of the spirochetes between these specimens could not be clearly confirmed. CONCLUSIONS: By increasing the feeding dynamics in females, the copulation of I. ricinus males with females attached to the host's skin may stimulate pathogen replication in tick tissues and migration from the gut to the salivary glands. Further investigations of the I. ricinus copulation on the host on female feeding and pathogen transmission may contribute to the elucidation of the eco-epidemiology of tick-borne diseases transmitted by this tick species.

The effect of cigarette smoke extract exposure on the size and sexual behaviour of Drosophila melanogaster.

Drosophila melanogaster is a widely used animal model in human diseases and to date it has not been applied to the study of the impact of tobacco use on human sexual function. Hence, this report examines the effects of different concentrations of cigarette smoke extract (CSE) exposure on the size and sexual behavior of D. melanogaster. Wild-type flies were held in vials containing CSE-infused culture media at concentrations of 10%, 25%, and 50% for three days, and their offspring were reared under the same conditions before measuring their body size and mating behavior. CSE exposure during development reduced the tibia length and body mass of emerging adult flies and prolonged the time required for successful courtship copulation success, while courtship behaviors (wing extension, tapping, abdomen bending, attempted copulation) remained largely unchanged. Our findings indicate that CSE exposure negatively affects the development of flies and their subsequent reproductive success. Future experiments should investigate the CSE effect on male female fertility.

Multiple mechanisms for inbreeding avoidance used simultaneously in a wild ape.

Mating with close kin can have considerable negative fitness consequences, which are expected to result in selective pressure for inbreeding avoidance mechanisms, such as dispersal, mate choice and post-copulatory biases. Captive studies have suggested that inbreeding avoidance through mate choice is far less widespread than expected and may be absent where other mechanisms already limit inbreeding. However, few studies have examined multiple mechanisms of inbreeding avoidance simultaneously, particularly in the wild. We use 13 years of detailed dispersal, copulation and paternity data from mountain gorillas to examine inbreeding avoidance. We find that partial dispersal of both sexes results in high kinship in multimale groups, but that copulations between close kin occur 40% less than expected. We find strong kin discrimination in mate choice, with significant avoidance of maternal kin but more limited avoidance of paternal kin. We find no evidence for post-copulatory inbreeding avoidance. Our analyses support familiarity-based mechanisms of kin identification and age-based avoidance that limits mating between fathers and daughters in their natal group. Our findings demonstrate that multiple complementary mechanisms for inbreeding avoidance can evolve in a single species and suggest that inbreeding avoidance through mate choice may enable more flexible dispersal systems to evolve.

Mating and post-copulation behavior in the tea leafhopper, Empoasca onukii (Hemiptera: Cicadellidae).

The tea leafhopper, Empoasca onukii, relies on substrate-borne vibrations for sexual communication and is mainly controlled with chemical pesticides, which poses risks to the environment and food safety. Based on previous studies, we conducted a series of behavioral assays by simultaneous observation of vibration signals and movement to investigate the mating and post-copulation behavior of tea leafhoppers. During mating, the activity of E. onukii was restricted to dawn and dusk and concentrated on the sixth or seventh mature leaf below the tea bud. By comparing the time spent in locating females among different males, the timely reply of females was the key factor affecting mating success. Empoasca onukii females mated only once in their lives, while males could mate multiple times. Male rivalry behavior involved two distinct strategies. The rivals could send disruptive pulses to overlap the male calling signals, locate the courting males, and drive them away after contact. Some rivals could emit mating disruption signals (MDSs) to interrupt the ongoing identification duet and establish their own mating communication. Both identification and location duets could be interrupted by playback of MDSs, which is essential to create effective synthetic signals to disrupt mating communication of E. onukii. Our study clarified the spatial and temporal distribution of E. onukii in mating and the function of MDSs, which will be essential to develop future vibrational mating disruption techniques for E. onukii and its energy-efficient application in the field.

Effects of different diets on Aedes aegypti adults: improving rearing techniques for sterile insect technique.

The aim was to evaluate the effect of different energy diets available in adulthood on the longevity, dispersal capacity and sexual performance of Aedes aegypti produced under a mass-rearing system. To evaluate the effects of diets in relation to the survival of the adult male insects of Ae. aegypti, six treatments were used: sucrose at a concentration of 10%, as a positive control (sack10); starvation, as a negative control (starvation); sucrose at a concentration of 20% associated with 1 g/l of ascorbic acid (sac20vitC); wild honey in a concentration of 10% (honey10); demerara sugar in a 10% concentration (demerara10); and sucrose at a concentration of 20% associated with 1 g/l of ascorbic acid and 0.5 g/l of amino acid proline (sac20vitCPr). Each treatment had 16 cages containing 50 adult males. For the tests of flight ability and propensity to copulation, five treatments were used (saca10; sac20vitC; mel10; demerara10; and sac20vitCPr), with males each for flight ability and females copulated by a single male for copulation propensity. The diet composed of sucrose at a concentration of 20% associated with ascorbic acid, as an antioxidant, improved the survival, flight ability and propensity to copulate in Ae. aegypti males under mass-rearing conditions, and may be useful to enhance the performance of sterile males, thus improving the success of sterile insect technique programmes.

The tight attachment achieved by the male discoidal setae is possibly a counter-adaptation to the grease layer on female integument surfaces in green dock beetles.

Green dock beetles Gastrophysa viridula exhibit sexual dimorphism in tarsal attachment setae: females have only pointed, lanceolate and spatula-like setae, while males additionally possess discoidal ones. The sexual dimorphism is probably attributed to the necessity of male discoidal setae to adhere to the smooth back of the female during copulation. We aimed to understand its possible mechanism of attachment with G. viridula. Pull-off forces of both females and males were measured on (i) alive females, (ii) dead and dried females, and (iii) resin replicas of fresh females. The attachment ability tended to increase on dead and replicated female surfaces in both sexes, which indicates that the epicuticular grease layer on the integument of alive intact beetles decreases the attachment. This tendency was prominent in females. The present study clearly showed that in G. viridula discoidal setae enable the males to adhere stronger to female surfaces. The divergent performance found between the sexes differing in their setal composition is probably caused by the stiffness difference between the setae types and by the specific shape of the setal tips. A peculiar reproductive biology in G. viridula is probably attributed to this remarkable divergence of labour in their attachment pads between the sexes.

Alternative reproductive tactics of unflanged and flanged male orangutans revisited.

In many slowly developing mammal species, males reach sexual maturity well before they develop secondary sexual characteristics. Sexually mature male orangutans have exceptionally long periods of developmental arrest. The two male morphs have been associated with behavioral alternative reproductive tactics, but this interpretation is based on cross-sectional analyses predominantly of Northwest Sumatran populations. Here we present the first longitudinal analyses of behavioral changes of 10 adult males that have been observed in both unflanged and flanged morph. We also analyzed long-term behavioral data on an additional 143 individually identified males from two study sites, Suaq (Sumatra, Pongo abelii) and Tuanan (Borneo, Pongo pygmaeus wurmbii), to assess male mating tactics cross-sectionally in relation to population, male morph (unflanged and flanged), and other socio-ecological factors. Both our longitudinal and cross-sectional results confirm and refine previous cross-sectional accounts of the differences in mating tactics between the unflanged and the flanged male morphs. In the unflanged morph, males exhibit higher sociability, particularly with females, and higher rates of both copulation and sexual coercion than in the flanged morph. Based on our results and those of previous studies showing that females prefer flanged males, and that flanged males have higher reproductive success, we conclude that unflanged males face a trade-off between avoiding male-male contest competition and gaining mating access to females, and thus follow a "best-of-a-bad-job" mating strategy.

Testing the Challenge Hypothesis in Stumptail Macaque Males: The Role of Testosterone and Glucocorticoid Metabolites in Aggressive and Mating Behavior.

The "challenge hypothesis" predicts higher male-male aggressive behavior along with increases in testosterone levels during times of reproductive challenges and social instability. In addition, in some primate species, higher glucocorticoid levels can be observed as well, but this is usually modulated by dominance rank. We studied rank-related aggressive behavior, mating activity, and fecal testosterone and glucocorticoid metabolites (fTm and fGCm) in male stumptail macaques (Macaca arctoides) in order to test some predictions of the "challenge hypothesis". Over a 20-month period, we collected data on aggressive behavior and copulation, as well as fecal samples (n = 700) to quantify fTm and fGCm in seven adult stumptail males living in captivity. During periods of mating activity, male-to-male aggression increased in higher- and middle-ranking males. Neither fTm nor fGCm levels predicted male-to-male aggression. fGCm levels (but not fTm) were positively associated with male-to-female aggression; however, this association was pronounced during periods of mating activity. fGCm levels differed according to social rank, with middle-ranking males having the highest levels. Both hormones were higher during periods of mating activity, but only in higher- and middle-ranking males. Taken together, our findings partially support the challenge hypothesis in a non-seasonal primate and shed some light on the unique social and mating system of the stumptail macaque.

Feeding on the Fruit Waste Orange Bagasse Modifies Immature Protein Content, Body Weight, Scent Bouquet Composition, and Copula Duration in Males of a Tephritid Frugivorous Fly.

Anastrepha ludens is a polyphagous frugivorous tephritid that infests citrus and mango. Here, we report the establishment of a laboratory colony of A. ludens reared on a larval medium that is a waste for the citrus industry, specifically, orange (Citrus × sinensis) fruit bagasse. After 24 generations of rearing on a nutritionally poor orange bagasse diet, pupae weighed 41.1% less than pupae from a colony reared on a nutritionally rich artificial diet. Larvae from the orange bagasse diet had 6.94% less protein content than larvae from the artificial diet, although their pupation rate was similar. Males from the orange bagasse diet produced a scent bouquet with 21 chemical compounds and were sexually competitive, but they had significantly shorter copulations when compared to males from the artificial diet and from the wild host, Casimiroa edulis, which had relatively simple scent bouquets. The chemical complexity in the odors of males from the orange bagasse diet might initially have attracted females to novel scent combinations, but, once in the copula, they may have been able to sense negative characteristics in males, leading them to terminate copulations soon after they began. We conclude that A. ludens can adjust morphological, life history, nutritional, and chemical traits when adapted to a larval environment consisting of fruit bagasse.

Sneaky copulations by subordinate males suggest direct fitness benefits from male-male associations in spotted bowerbirds (Ptilonorhynchus maculatus).

Male spotted bowerbirds (Ptilonorhynchus maculatus) build and defend a structure of sticks and straw-the bower-decorated with colourful objects to attract mates during the breeding season. Specific non-territorial, subordinate males are tolerated by resident males at bowers over multiple breeding seasons. Prior research showed that these male-male associations exhibit attributes of coalitionary behaviour and that subordinate males gain delayed benefits from associating with bower owners, namely future bower inheritance. Yet, it remained unclear whether subordinate males may additionally gain direct fitness benefits from attending established bowers. Here, we report on four separate instances of sneaky copulations (or attempts of copulating) by subordinate males at resident males' bowers. Multiple non-resident males disrupted the ongoing copulations between the bower owner and a receptive female, and these events were followed by violent aggressive interactions. These observations shed new light on same-sex social dynamics in spotted bowerbirds and support the hypothesis that subordinate males are sexually mature individuals that occasionally obtain access to females while attending established bowers. We discuss these findings in light of the literature on male courtship coalitions and agonistic behaviour in bowerbirds, and highlight further aspects of subordinate behaviour that require empirical investigation.

Pathologic copulatory lock in a genetically engineered laboratory mouse breeding pair.

A breeding pair of genetically engineered laboratory mice (Mus musculus) presented in apparent copulatory lock (coital tie). After anesthetizing the animals, gentle traction was used to separate the pair at which point a vaginal prolapse was detected and the penis was covered with black, firm, dry crusts and noted to have a solid pale, tan, firm cylindrical mass adhering to its glans. The vaginal prolapse was reduced and the female was returned to its cage. The male mouse had a severely distended bladder which could not be expressed and was euthanized. Histopathologic examination of the distal two-thirds of the penis revealed diffuse, acute coagulative necrosis. The mass adhered to the distal penis was a homogenous granular eosinophilic material consistent with a copulatory plug. While copulatory plugs and locks have been described in some rodent species, they have not been reported in laboratory mice. While the cause of the adherence of the plug to the penis could not be determined, we hypothesize that its adherence to both the penis and the vagina led to the lock and subsequently to ischemic necrosis of the distal penis.

Sperm Competition Risk: The Connections That Partner Attractiveness and Infidelity Risk Have with Mate Retention Behaviors and Semen-Displacing Behaviors.

The present studies investigated the relationships between men's perceived risk of experiencing sperm competition (i.e., when the ejaculates of two or more men simultaneously occupy the reproductive tract of a single woman), and their use of strategies to detect, prevent, and correct their partner's sexual infidelity. We investigated these associations using self-reports provided by men (Study 1, n = 113), partner-reports provided by women (Study 2, n = 136), and dyadic reports (Study 3, n = 103 couples). The results of these studies indicated that the attractiveness of women was consistently associated with men's use of benefit-provisioning mate retention behaviors (e.g., buying expensive gifts for one's partner, showing signs of physical affection) and semen-displacing behaviors (e.g., deeper copulatory thrusting, more thrusts during copulation), whereas the infidelity risk of women was often associated with men's use of cost-inflicting mate retention behaviors (e.g., threatening to end the relationship, monopolization of partner's free time). Discussion addresses the evolutionary implications of these results, including the possibility that men use both benefit-provisioning mate retention behaviors and semen-displacing behaviors when they perceive their partner to be more attractive, ostensibly as a way to mitigate their risk of sperm competition. Discussion also explores the extent to which these results extend those of previous studies concerning sperm competition risk.

Intestinal Immune Deficiency and Juvenile Hormone Signaling Mediate a Metabolic Trade-off in Adult Drosophila Females.

A trade-off hypothesis pertains to the biased allocation of limited resources between two of the most important fitness traits, reproduction and survival to infection. This quid pro quo manifests itself within animals prioritizing their energetic needs according to genetic circuits balancing metabolism, germline activity and immune response. Key evidence supporting this hypothesis includes dipteran fecundity being compromised by systemic immunity, and female systemic immunity being compromised by mating. Here, we reveal a local trade-off taking place in the female Drosophila midgut upon immune challenge. Genetic manipulation of intestinal motility, permeability, regeneration and three key midgut immune pathways provides evidence of an antagonism between specific aspects of intestinal defense and fecundity. That is, juvenile hormone (JH)-controlled egg laying, lipid droplet utilization and insulin receptor expression are specifically compromised by the immune deficiency (Imd) and the dual oxidase (Duox) signaling in the midgut epithelium. Moreover, antimicrobial peptide (AMP) expression under the control of the Imd pathway is inhibited upon mating and JH signaling in the midgut. Local JH signaling is further implicated in midgut dysplasia, inducing stem cell-like clusters and gut permeability. Thus, midgut JH signaling compromises host defense to infection by reducing Imd-controlled AMP expression and by inducing dysplasia, while midgut signaling through the Imd and Duox pathways compromises JH-guided metabolism and fecundity.

Reciprocal effects of single or repeated exposure to methylphenidate or sex in adult male rats.

RATIONALE: Exposure to rewards can alter behavioral reactivity to them. For example, stimulants sensitize locomotor activation, whereas sexual experience sensitizes copulatory behaviors. Moreover, rewards can cross-sensitize one another. Although stimulants are known to cross-sensitize locomotor effects, the evidence for cross-sensitization between stimulants and sex is less clear. OBJECTIVES: This study determined the effects of single and repeated pre-exposure to methylphenidate (MPH) or sex on one another in adult male rats. METHODS: Cross-sensitization between MPH (5 mg/kg) and sex (30 min with sexually experienced female) was examined. Adult male rats were pre-exposed to 0, 1, or 10 trials of either sex or MPH before being exposed to the other reward. Locomotor chambers were used in MPH trials. Bilevel chambers were used in sexual trials, and sexual behaviors were video scored. RESULTS: The amount of prior sexual experience differentially influenced the ceiling of MPH-dependent sensitization; in the last drug trial, locomotion was highest in males given 1 previous sexual trial compared with 0 or 10. Compared with MPH-naive males, pre-exposure to MPH (1 and 10 trials) reduced the number of ejaculations without impacting sexual performance (intromission/mount latency and frequency). CONCLUSIONS: These findings indicate that the degree of pre-exposure to a reward can differentially affect reactivity to novel rewards. The results showed that previous findings of cross-sensitization between amphetamine and sex do not extend to MPH. However, exposure to MPH prior to sexual experience can increase the amount of sexual stimulation needed to achieve ejaculation.