The neurobiology of the male sexual refractory period

Repeated sexual intercourse as a coping strategy for men with premature ejaculation

BACKGROUND

Patients with premature ejaculation (PE) are often concerned and distressed about their sexual performance. Hence, they may be more willing to exploit their refractory period to employ sexual coping strategies in order to improve their unsatisfactory sexual intercourse compared with patients without PE.

AIM

The study sought to verify the sexual coping strategies of patients with PE in the daily sexual activities.

METHODS

We included both patients with PE and individuals without PE and analyzed their sexual behaviors and attitudes by means of detailed interviews and questionnaires.

OUTCOMES

The main outcomes were perceived intravaginal ejaculatory latency time recording, Premature Ejaculation Diagnostic Tool score, and sexual frequency, attitudes, and behavior log.

RESULTS

A total of 182 young patients with PE (age 31.2 ± 6.2 years) and 92 individuals without PE (age 30.7 ± 5.1 years) were included in the study. A total of 53.3% of patients with PE vs 17.4% of individuals without PE reported engaging in multiple sexual intercourse sessions within a single day in the past 4 weeks. PE patients who engaged in multiple intercourse sessions displayed better performance during the second attempt but performed poorly compared with individuals without PE. Scores for the first attempt in PE vs second attempt in individuals with PE vs without PE were the following: intravaginal ejaculatory latency time, 2.4 ± 1.6 vs 4.8 ± 5.7 vs 9.9 ± 9.4 (P < .001); Premature Ejaculation Diagnostic Tool, 14.9 ± 3.1 vs 12.7 ± 4.8 vs 5.2 ± 2.5 (P < .001); satisfaction, 2.9 ± 1.0 vs 3.1 ± 0.8 vs 3.7 ± 1.4 (P < .001). A total of 57.1% of patients held a negative attitude toward precoital masturbation, for reasons such as a reduced sexual desire (21.2%), the belief that masturbation is harmful (17.6%), concerns about erectile function (15.7%), fatigue (9.8%), and other mixed reasons (35.3%).

CLINICAL IMPLICATIONS

Engaging in multiple intercourse sessions within a day is more common among the young PE population, and using precoital masturbation as a coping strategy is not universally applicable among patients with PE.

STRENGTHS AND LIMITATIONS

This is the first study to explore symptom-coping strategies in patients with PE compared with individuals without PE. However, the conclusions cannot be generalized to the entire male population.

CONCLUSION

Patients with PE, compared with individuals without PE, are more inclined to engage in multiple sexual intercourse sessions within a single sexual session, likely in an attempt to compensate for their first unsatisfactory sexual encounter. Moreover, the majority of patients with PE here studied hold a negative attitude toward using precoital masturbation as a coping strategy for symptoms.

Estrogen-responsive neural circuits governing male and female mating behavior in mice

Decades of knockout analyses have highlighted the crucial involvement of estrogen receptors and downstream genes in controlling mating behaviors. More recently, advancements in neural circuit research have unveiled a distributed subcortical network comprising estrogen-receptor or estrogen-synthesis-enzyme-expressing cells that transforms sensory inputs into sex-specific mating actions. This review provides an overview of the latest discoveries on estrogen-responsive neurons in various brain regions and the associated neural circuits that govern different aspects of male and female mating actions in mice. By contextualizing these findings within previous knockout studies of estrogen receptors, we emphasize the emerging field of "circuit genetics", where identifying mating behavior-related neural circuits may allow for a more precise evaluation of gene functions within these circuits. Such investigations will enable a deeper understanding of how hormone fluctuation, acting through estrogen receptors and downstream genes, influences the connectivity and activity of neural circuits, ultimately impacting the manifestation of innate mating actions.

Neural control of female sexual behaviors

Reproduction is the biological process by which new individuals are produced by their parents. It is the fundamental feature of all known life and is required for the existence of all species. All mammals reproduce sexually, a process that involves the union of two reproductive cells, one from a male and one from a female. Sexual behaviors are a series of actions leading to reproduction. They are composed of appetitive, action, and refractory phases, each supported by dedicated developmentally-wired neural circuits to ensure high reproduction success. In rodents, successful reproduction can only occur during female ovulation. Thus, female sexual behavior is tightly coupled with ovarian activity, namely the estrous cycle. This is achieved through the close interaction between the female sexual behavior circuit and the hypothalamic-pituitary-gonadal (HPG) axis. In this review, we will summarize our current understanding, learned mainly in rodents, regarding the neural circuits underlying each phase of the female sexual behaviors and their interaction with the HPG axis, highlighting the gaps in our knowledge that require future investigation.

Neural circuit control of innate behaviors

All animals possess a plethora of innate behaviors that do not require extensive learning and are fundamental for their survival and propagation. With the advent of newly-developed techniques such as viral tracing and optogenetic and chemogenetic tools, recent studies are gradually unraveling neural circuits underlying different innate behaviors. Here, we summarize current development in our understanding of the neural circuits controlling predation, feeding, male-typical mating, and urination, highlighting the role of genetically defined neurons and their connections in sensory triggering, sensory to motor/motivation transformation, motor/motivation encoding during these different behaviors. Along the way, we discuss possible mechanisms underlying binge-eating disorder and the pro-social effects of the neuropeptide oxytocin, elucidating the clinical relevance of studying neural circuits underlying essential innate functions. Finally, we discuss some exciting brain structures recurrently appearing in the regulation of different behaviors, which suggests both divergence and convergence in the neural encoding of specific innate behaviors. Going forward, we emphasize the importance of multi-angle and cross-species dissections in delineating neural circuits that control innate behaviors.

Exploring Male Multiple Orgasm in a Large Online Sample: Refining Our Understanding

BACKGROUND

The scientific literature on multiple orgasm in males is small. There is little consensus on a definition, and significant controversy about whether multiple orgasm is a unitary experience.

AIMS

This study has 2 goals: (i) describing the experience of male multiple orgasm; (ii) investigating whether there are different profiles of multiple orgasm in men.

METHODS

Data from a culturally diverse online convenience sample of 122 men reporting multiple orgasm were collected. Data reduction analyses were conducted using principal components analysis (PCA) on 13 variables of interest derived from theory and the existing literature. A K-means cluster analysis followed, from which a 4-cluster solution was retained.

RESULTS

While the range of reported orgasms varied from 2 to 30, the majority (79.5%, N = 97) of participants experienced between 2 and 4 orgasms separated by a specific time interval during which further stimulation was required to achieve another orgasm. Most participants reported maintaining their erections throughout and ejaculating with every orgasm. Age was not a significant correlate of the multiple orgasm experience which occurred more frequently in a dyadic context. Four different profiles of multiorgasmic men were described.

STRENGTHS & LIMITATIONS

This study constitutes a rare attempt to collect systematic self-report data concerning the experience of multiple orgasm in a relatively large sample. Limitations include the lack of validated measures, memory bias associated with self-reported data and retrospective designs, the lack of a control group and of physiological measurement.

CONCLUSION

Our study suggests that multiple orgasm in men is not a unitary phenomenon and sets the stage for future self-report and laboratory study. Griffin-Mathieu G, Berry M, Shtarkshall RA, Amsel R, Binik YM, Gérard M. Exploring Male Multiple Orgasm in a Large Online Sample: Refining Our Understanding. J Sex Med 2021;XX:XXX-XXX.

Male rat sexual behavior: Insights from inter-copulatory intervals

The assessment of sexual behavior in male rats with the aim of unraveling underlying neurobiological mechanisms has in the recent decades been reduced to the annotation of mounts, intromissions and ejaculations. To provide a better understanding of the structure and patterns of copulation, it is necessary to extend and tailor the analysis to the natural organization of male rat copulation. This will lead to better formulation of hypotheses about neurobiological underpinnings of behavior. Mounts and intromissions are naturally organized in mount bouts consisting of one or more copulatory behaviors and are interspersed with time outs. We hypothesized that time outs and the post-ejaculatory interval (inter-copulatory intervals) are related and possibly under the control of a common copulatory inhibition mechanism that is the result of penile sensory stimulation. To test this hypothesis, we analyzed sexual behavior in male rats of three different cohorts from three different laboratories. Results showed that the post-ejaculatory interval and mean time out duration are strongly correlated in all cohorts analyzed. In addition, we showed that individual time out duration is at least partially predicted by the sum of sensory stimulation of copulatory components in the preceding mount bout, with more penile stimulation associated with longer time outs. These findings suggest that both time out and post-ejaculatory interval duration may be determined by the magnitude of sensory stimulation, which inhibits copulation. Whether the same neural pathways are involved in the central orchestration of both time outs and the post-ejaculatory interval should be subject to future studies.

The Rare Phenomenon of Consecutive Ejaculations in Male Rats

Mounting, intromission and ejaculation are commonly reported sexual behaviours in male rats. In a mating session, they can have several copulatory series with post-ejaculatory intervals in between ejaculations before they reach sexual satiety. Here, we describe a phenomenon where male rats displayed consecutive ejaculations (CE) with a short inter-ejaculatory interval (IEI). Male rats were daily mated with a sexually receptive female rat. Two out of 15 rats displayed CE in one of their mating tests. The first rat had CE at 9.9 and 10.1 min (IEI = 16.3 s) after the start of the test. The second rat showed CE at 28.1 and 28.5 min (IEI = 18.7 s) after the test onset. During the IEI, the rats did not show any mounting or intromission.

No evidence for prolactin's involvement in the post-ejaculatory refractory period

In many species, ejaculation is followed by a state of decreased sexual activity, the post-ejaculatory refractory period. Several lines of evidence have suggested prolactin, a pituitary hormone released around the time of ejaculation in humans and other animals, to be a decisive player in the establishment of the refractory period. However, data supporting this hypothesis is controversial. We took advantage of two different strains of house mouse, a wild derived and a classical laboratory strain that differ substantially in their sexual performance, to investigate prolactin's involvement in sexual activity and the refractory period. First, we show that there is prolactin release during sexual behavior in male mice. Second, using a pharmacological approach, we show that acute manipulations of prolactin levels, either mimicking the natural release during sexual behavior or inhibiting its occurrence, do not affect sexual activity or shorten the refractory period, respectively. Therefore, we show compelling evidence refuting the idea that prolactin released during copulation is involved in the establishment of the refractory period, a long-standing hypothesis in the field of behavioral endocrinology.

Challenging the Standard Model of Sexual Response: Evidence of a Variable Male Sexual Response Cycle

Historically the male sexual response cycle was seen as uniform and used as the standard for women. Recent research has suggested that men's sexual response cycle may vary more than previously thought. We asked 520 sexually active men between the ages of 18-73 to report on their sexual desire and arousal patterns during their last sexual experience. Using a latent class mixture model from retrospective sexual response data, we found five classes of desire and arousal patterns. These patterns were examined for associations with demographics, outcomes during the sexual experience, and outcomes for the global relationship. The experiences of arousal and desire appear to be indistinguishable for men in this sample. The Fluctuation sexual response class (19% of men) and the High sexual response class (40%) were significantly different from most of the other classes in duration of their sexual experiences and overall satisfaction with their sexual experiences. Still, most sexual response patterns were associated with healthy relational and sexual outcomes. Variability in the male sexual response cycle is important to acknowledge and normalize.

Patterns of prolactin secretion

Prolactin is pleotropic in nature affecting multiple tissues throughout the body. As a consequence of the broad range of functions, regulation of anterior pituitary prolactin secretion is complex and atypical as compared to other pituitary hormones. Many studies have provided insight into the complex hypothalamic-pituitary networks controlling prolactin secretion patterns in different species using a range of techniques. Here, we review prolactin secretion in both males and females; and consider the different patterns of prolactin secretion across the reproductive cycle in representative female mammals with short versus long luteal phases and in seasonal breeders. Additionally, we highlight changes in the pattern of secretion during pregnancy and lactation, and discuss the wide range of adaptive functions that prolactin may have in these important physiological states.

The Sexual Motivation of Male Rats as a Tool in Animal Models of Human Health Disorders

Normal or dysfunctional sexual behavior seems to be an important indicator of health or disease. Many health disorders in male patients affect sexual activity by directly causing erectile dysfunction, affecting sexual motivation, or both. Clinical evidence indicates that many diseases strongly disrupt sexual motivation and sexual performance in patients with depression, addiction, diabetes mellitus and other metabolic disturbances with obesity and diet-related factors, kidney and liver failure, circadian rhythm disorders, sleep disturbances including obstructive sleep apnea syndrome, developmental and hormonal disorders, brain damages, cardiovascular diseases, and peripheral neuropathies. Preclinical studies of these conditions often require appropriate experimental paradigms, including animal models. Male sexual behavior and motivation have been intensively investigated over the last 80 years in animal rat model. Sexual motivation can be examined using such parameters as: anticipatory behavior and 50-kHz ultrasonic vocalizations reflecting the emotional state of rats, initiation of copulation, efficiency of copulation, or techniques of classical (pavlovian) and instrumental conditioning. In this review article, we analyze the behavioral parameters that describe the sexual motivation and sexual performance of male rats in the context of animal experimental models of human health disorders. Based on analysis of the parameters describing the heterogeneous and complex structure of sexual behavior in laboratory rodents, we propose an approach that is useful for delineating distinct mechanisms affecting sexual motivation and sexual performance in selected disease states and the efficacy of therapy in preclinical investigations.

Modeling Human Sexual Motivation in Rodents: Some Caveats

Sexual behavior is activated by motivation. An overwhelming majority of experimental studies of the intricacies of sexual motivation has been performed in rodents, most of them in rats. Sometimes it is desirable to generalize results obtained in this species to other species, particularly the human. It is hoped that studies of the neurobiology of rodent sexual behavior may shed light on the central nervous mechanisms operating in the human, and the search for efficient pharmacological treatments of human sexual dysfunctions relies partly on studies performed in rodents. Then the issue of generalizability of the rodent data to the human becomes crucial. We emphasize the importance of distinguishing between copulatory acts, behavior involving the genitals, and the preceding event, the establishment of physical contact with a potential mate. Comparisons between the structure of copulatory behavior in rats and humans show abysmal differences, but there may be some similarity in the underlying mechanisms. The endocrine control of sex behavior is shortly mentioned, and we also compare the effects of the few drugs known to affect both rodent and human copulatory behavior. The stimuli activating sexual motivation, often called desire in the human literature, are examined, and the sexual approach behaviors in rats and humans are compared. There is a striking similarity between these species in how these behaviors respond to drugs. It is then shown that the intensity of sexual approach is unrelated to the intensity of copulatory behavior. Even though the approach is a requisite for copulation, an activity that requires at least two individuals in close physical contact, these two aspects of sexuality do not covary. This is similar to the role of the testosterone in men and male rats: although the hormone is needed for sex behavior, there is no correlation between serum testosterone concentration and the intensity of copulation. It is also pointed out that human sexual behavior is mostly determined by social conventions, whereas this is not the case in rats and other rodents. It is concluded that some observations in rats can be generalized to the human, but extreme caution must be exercised.