Hormone-neurotransmitter interactions in the control of sexual behavior

Sexual Desire and Pharmacologic Management

Female sexual desire is a complex interplay of neurotransmitters and hormones. Diagnosis is based on clinical features and sexual distress. Treatments that affect neurotransmitters and hormones that may be out of balance can help improve sexual desire in women with hypoactive sexual desire disorder.

Post-stress Social Interaction and 3-Cyano-N-(1,3-Diphenyl-1H-Pyrazol-5-yl) Benzamide Treatment Attenuate Depressive-like Behavior Induced by Repeated Social Defeat Stress

Persistent stress increases the probability for developing depression significantly thereafter. Repeated social defeat stress is a widely used model to investigate depressive-like behavior in preclinical models. Hence, the repeated social defeat stress model provided an ideal animal model, through which the hypotheses of prevention and treatment can be investigated. We have successfully induced depressive-like behavior for male C57BL/6J mice with this model. Here, we reported that certain level of during-stress social interactions with single female or multiple male peer(s) exerted a positive role in preventing the development of depressive-like behavior induced by repeated social defeat stress. Our data suggested that the stress-susceptible mice may benefit from positive social interaction, which reduces the chance for depressive-like behavior development. Since numerous studies indicate that the metabotropic glutamate receptor 5 (mGluR5) plays an important role in various cognitive functions, we further investigate the treatment effect of 3-cyano-N-(1,3-diphenyl-1H-pyrazol-5-yl) benzamide (CDPPB) on the depressive-like behavior induced by repeated social defeat stress. Most importantly, robust anti-depressant effects have been achieved through modulating the mGluR5 function. We found that single oral dose administration of CDPPB (20 mg/kg), to some extent, alleviated the social avoidance behaviors for the stress-susceptible mice. Our data implies that the CDPPB, a positive allosteric modulator of mGluR5, is a promising anti-depressant candidate with limited side effect.

Neurophysiology of male sexual arousal-Behavioral perspective

In the presented review, we analyzed the physiology of male sexual arousal and its relation to the motivational aspects of this behavior. We highlighted the distinction between these processes based on observable physiological and behavioral parameters. Thus, we proposed the experimentally applicable differentiation between sexual arousal (SA) and sexual motivation (SM). We propose to define sexual arousal as an overall autonomic nervous system response leading to penile erection, triggered selectively by specific sexual cues. These autonomic processes include both spinal and supraspinal neuronal networks, activated by sensory pathways including information from sexual partner and sexual context, as well as external and internal genital organs. To avoid misinterpretation of experimental data, we also propose to precise the term "sexual motivation" as all actions performed by the individual that increase the probability of sexual interactions or increase the probability of exposition to sexual context cues. Neuronal structures such as the amygdala, bed nucleus of stria terminalis, hypothalamus, nucleus raphe, periaqueductal gray, and nucleus paragigantocellularis play crucial roles in controlling the level of arousal and regulating peripheral responses via specific autonomic effectors. On the highest level of CNS, the activity of cortical structures involved in the regulation of the autonomic nervous system, such as the insula and anterior cingulate cortex, can visualize an elevated level of SA in both animal and human brains. From a preclinical perspective, we underlie the usefulness of the non-contact erection test (NCE) procedure in understanding factors influencing sexual arousal, including studies of sexual preference in animal models. Taken together results obtained by different methods, we wanted to focus attention on neurophysiological aspects that are distinctly related to sexual arousal and can be used as an objective parameter, leading to higher translational transparency between basic, preclinical, and clinical studies.

The elusive concept of sexual motivation: can it be anchored in the nervous system?

Sexual motivation is an abstract concept referring to the mechanisms determining the responsivity to sexually relevant stimuli. This responsivity determines the likelihood of producing a sexual response and the intensity of that response. Both responsivity to stimuli and the likelihood of making a response as well as the intensity of response are characteristics of an individual. Therefore, we need to assume that the concept of sexual motivation materializes in physiological mechanisms within the individual. The aim of the present communication is to analyze the requisites for the endeavor to materialize sexual motivation. The first requisite is to provide an operational definition, making the concept quantifiable. We show that parameters of copulatory behavior are inappropriate. We argue that the intensity of sexual approach behaviors provides the best estimate of sexual motivation in non-human animals, whereas the magnitude of genital responses is an exquisite indicator of human sexual motivation. Having assured how to quantify sexual motivation, we can then proceed to the search for physiological or neurobiological underpinnings. In fact, sexual motivation only manifests itself in animals exposed to appropriate amounts of gonadal hormones. In female rats, the estrogen receptor α in the ventrolateral part of the ventromedial nucleus of the hypothalamus is necessary for the expression of sexual approach behaviors. In male rats, androgen receptors within the medial preoptic area are crucial. Thus, in rats sexual motivation can be localized to specific brain structures, and even to specific cells within these structures. In humans, it is not even known if sexual motivation is materialized in the brain or in peripheral structures. Substantial efforts have been made to determine the relationship between the activity of neurotransmitters and the intensity of sexual motivation, particularly in rodents. The results of this effort have been meager. Likewise, efforts of finding drugs to stimulate sexual motivation, particularly in women complaining of low sexual desire, have produced dismal results. In sum, it appears that the abstract concept of sexual motivation can be reliably quantified, and the neurobiological bases can be described in non-human animals. In humans, objective quantification is feasible, but the neurobiological substrate remains enigmatic.

Hormone therapy for sexual function in perimenopausal and postmenopausal women

BACKGROUND

The perimenopausal and postmenopausal periods are associated with many symptoms, including sexual complaints. This review is an update of a review first published in 2013.

OBJECTIVES

We aimed to assess the effect of hormone therapy on sexual function in perimenopausal and postmenopausal women.

SEARCH METHODS

On 19 December 2022 we searched the Gynaecology and Fertility Group Specialised Register, CENTRAL, MEDLINE, Embase, PsycINFO, CINAHL, LILACS, ISI Web of Science, two trials registries, and OpenGrey, together with reference checking and contact with experts in the field for any additional studies.

SELECTION CRITERIA

We included randomized controlled trials that compared hormone therapy to either placebo or no intervention (control) using any validated assessment tool to evaluate sexual function. We considered hormone therapy: estrogen alone; estrogen in combination with progestogens; synthetic steroids, for example, tibolone; selective estrogen receptor modulators (SERMs), for example, raloxifene, bazedoxifene; and SERMs in combination with estrogen.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures recommended by Cochrane. We analyzed data using mean differences (MDs) and standardized mean differences (SMDs). The primary outcome was the sexual function score. Secondary outcomes were the domains of sexual response: desire; arousal; lubrication; orgasm; satisfaction; and pain. We assessed the certainty of the evidence using the GRADE approach.

MAIN RESULTS

We included 36 studies (23,299 women; 12,225 intervention group; 11,074 control group), of which 35 evaluated postmenopausal women; only one study evaluated perimenopausal women. The 'symptomatic or early postmenopausal women' subgroup included 10 studies, which included women experiencing menopausal symptoms (symptoms such as hot flushes, night sweats, sleep disturbance, vaginal atrophy, and dyspareunia) or early postmenopausal women (within five years after menopause). The 'unselected postmenopausal women' subgroup included 26 studies, which included women regardless of menopausal symptoms and women whose last menstrual period was more than five years earlier. No study included only women with sexual dysfunction and only seven studies evaluated sexual function as a primary outcome. We deemed 20 studies at high risk of bias, two studies at low risk, and the other 14 studies at unclear risk of bias. Nineteen studies received commercial funding. Estrogen alone versus control probably slightly improves the sexual function composite score in symptomatic or early postmenopausal women (SMD 0.50, 95% confidence interval (CI) (0.04 to 0.96; I² = 88%; 3 studies, 699 women; moderate-quality evidence), and probably makes little or no difference to the sexual function composite score in unselected postmenopausal women (SMD 0.64, 95% CI -0.12 to 1.41; I² = 94%; 6 studies, 608 women; moderate-quality evidence). The pooled result suggests that estrogen alone versus placebo or no intervention probably slightly improves sexual function composite score (SMD 0.60, 95% CI 0.16 to 1.04; I² = 92%; 9 studies, 1307 women, moderate-quality evidence). We are uncertain of the effect of estrogen combined with progestogens versus placebo or no intervention on the sexual function composite score in unselected postmenopausal women (MD 0.08 95% CI -1.52 to 1.68; 1 study, 104 women; very low-quality evidence). We are uncertain of the effect of synthetic steroids versus control on the sexual function composite score in symptomatic or early postmenopausal women (SMD 1.32, 95% CI 1.18 to 1.47; 1 study, 883 women; very low-quality evidence) and of their effect in unselected postmenopausal women (SMD 0.46, 95% CI 0.07 to 0.85; 1 study, 105 women; very low-quality evidence). We are uncertain of the effect of SERMs versus control on the sexual function composite score in symptomatic or early postmenopausal women (MD -1.00, 95% CI -2.00 to -0.00; 1 study, 215 women; very low-quality evidence) and of their effect in unselected postmenopausal women (MD 2.24, 95% 1.37 to 3.11 2 studies, 1525 women, I² = 1%, low-quality evidence). We are uncertain of the effect of SERMs combined with estrogen versus control on the sexual function composite score in symptomatic or early postmenopausal women (SMD 0.22, 95% CI 0.00 to 0.43; 1 study, 542 women; very low-quality evidence) and of their effect in unselected postmenopausal women (SMD 2.79, 95% CI 2.41 to 3.18; 1 study, 272 women; very low-quality evidence). The observed heterogeneity in many analyses may be caused by variations in the interventions and doses used, and by different tools used for assessment.

AUTHORS' CONCLUSIONS

Hormone therapy treatment with estrogen alone probably slightly improves the sexual function composite score in women with menopausal symptoms or in early postmenopause (within five years of amenorrhoea), and in unselected postmenopausal women, especially in the lubrication, pain, and satisfaction domains. We are uncertain whether estrogen combined with progestogens improves the sexual function composite score in unselected postmenopausal women. Evidence regarding other hormone therapies (synthetic steroids and SERMs) is of very low quality and we are uncertain of their effect on sexual function. The current evidence does not suggest the beneficial effects of synthetic steroids (for example tibolone) or SERMs alone or combined with estrogen on sexual function. More studies that evaluate the effect of estrogen combined with progestogens, synthetic steroids, SERMs, and SERMs combined with estrogen would improve the quality of the evidence for the effect of these treatments on sexual function in perimenopausal and postmenopausal women.

Mechanisms Suggesting a Relationship between Vitamin D and Erectile Dysfunction: An Overview

Vitamin D deficiency (VDD) and erectile dysfunction (ED) heavily burden the male population. The higher prevalence of both conditions in the elderly suggests a possible relationship between the two conditions. In addition, in vitro, animal, and human studies have revealed several mechanisms that may relate VDD to ED. The main mechanism by which vitamin D might exert its action on sexual function appears to be through the regulation of endothelial function. Indeed, VDD correlates with several markers of endothelial function. The action of vitamin D on the endothelium would be exercised both indirectly through its intervention in inflammatory processes and through the production of oxygen free radicals, and directly through the regulation of vascular stiffness, the production of nitric oxide, and the regulation of vessel permeability. Furthermore, the ubiquitous distribution of the vitamin D receptor in the human body means that this hormone can also exert a beneficial effect on erectile function by interfering with those comorbidities significantly associated with ED, such as hypertension, diabetes mellitus, hypercholesterolemia, chronic kidney disease, and hypogonadism. In this review, we thoroughly and carefully presented the evidence and mechanisms that would appear to relate vitamin D levels to erectile function. Furthermore, we have summarized the meta-analytic evidence for and against this association to provide a true representation of this topic. Data published to date suggest that low levels of vitamin D could contribute to worsening erectile function through several mechanisms. Therefore, vitamin D levels should be measured in patients with ED and maintained at adequate levels by specific supplementation in case of deficiency. However, the low quality and heterogeneity of clinical trials evaluating the effects of vitamin D administration on erectile function and ED-associated comorbidities do not allow for a univocal conclusion, and indicate the need for further studies to analyze these aspects.

Methoprene-tolerant and Krüppel homolog 1 are actors of juvenile hormone-signaling controlling the development of male sexual behavior in the moth Agrotis ipsilon

In insects, juvenile hormone (JH) is critical for the orchestration of male reproductive maturation. For instance, in the male moth, Agrotis ipsilon, the behavioral response and the neuronal sensitivity within the primary olfactory centers, the antennal lobes (ALs), to the female-emitted sex pheromone increase with fertility during adulthood and the coordination between these events is governed by JH. However, the molecular basis of JH action in the development of sexual behavior remains largely unknown. Here, we show that the expression of the paralogous JH receptors, Methoprene-tolerant 1 and 2 (Met1, Met2) and of the JH-inducible transcription factor, Krüppel homolog 1 (Kr-h1) within ALs raised from the third day of adult life and this dynamic is correlated with increased behavioral responsiveness to sex pheromone. Met1-, Met2- and Kr-h1-depleted sexually mature males exhibited altered sex pheromone-guided orientation flight. Moreover, injection of JH-II into young males enhanced the behavioral response to sex pheromone with increased AL Met1, Met2 and Kr-h1 mRNA levels. By contrast, JH deficiency suppressed the behavioral response to sex pheromone coupled with reduced AL Met1, Met2 and Kr-h1 mRNA levels in allatectomized old males and these inhibitions were compensated by an injection of JH-II in operated males. Our results demonstrated that JH acts through Met-Kr-h1 signaling pathway operating in ALs, to promote the pheromone information processing and consequently the display of sexual behavior in synchronization with fertility to optimize male reproductive fitness. Thus, this study provides insights into the molecular mechanisms underlying the hormonal regulation of reproductive behavior in insects.

Dopamine, Erectile Function and Male Sexual Behavior from the Past to the Present: A Review

Early and recent studies show that dopamine through its neuronal systems and receptor subtypes plays different roles in the control of male sexual behavior. These studies show that (i) the mesolimbic/mesocortical dopaminergic system plays a key role in the preparatory phase of sexual behavior, e.g., in sexual arousal, motivation and reward, whereas the nigrostriatal system controls the sensory-motor coordination necessary for copulation, (ii) the incertohypothalamic system is involved in the consummatory aspects of sexual behavior (penile erection and copulation), but evidence for its role in sexual motivation is also available, (iii) the pro-sexual effects of dopamine occur in concert with neural systems interconnecting the hypothalamus and preoptic area with the spinal cord, ventral tegmental area and other limbic brain areas and (iv) D₂ and D₄ receptors play a major role in the pro-sexual effects of dopamine. Despite some controversy, increases or decreases, respectively, of brain dopamine activity induced by drugs or that occur physiologically, usually improves or worsens, respectively, sexual activity. These findings suggest that an altered central dopaminergic tone plays a role in mental pathologies characterized by aberrant sexual behavior, and that pro-erectile D₄ receptor agonists may be considered a new strategy for the treatment of erectile dysfunction in men.

Clinical Study on the Use of Acupuncture for the Treatment of Female Sexual Dysfunction: A Pilot Study

Introduction

Female sexual dysfunction (FSD) seriously affects the quality of life of women. However, most women do not have access to effective treatment.

Aim

This study aimed to determine the feasibility and effectiveness of the use of acupuncture in FSD treatment based on existing clear acupuncture protocol and experience-supported face-to-face therapy.

Methods

A retrospective analysis was performed on 24 patients with FSD who received acupuncture from October 2018 to February 2022. The Chinese version of the female sexual function index , subjective sensation, sexual desire, sexual arousal, vaginal lubrication, orgasm, sexual satisfaction, and dyspareunia scores were compared before and after the treatment in all 24 patients.

Main Outcome Measure

A specific female sexual function index questionnaire was used to assess changes in female sexual function before and after the acupuncture treatment.

Results

In this study, the overall treatment improvement rate of FSD was 100%. The Chinese version of the female sexual function index total score, sexual desire score, sexual arousal score, vaginal lubrication score, orgasm score, sexual satisfaction score, and dyspareunia score during intercourse were significantly different before and after the treatment (P < .05). Consequently, participants reported high levels of satisfaction with acupuncture. This study indicates that acupuncture could be a new and effective technique for treating FSD. The main advantages of this study are its design and efficacy in treating FSD. To the best of our knowledge, this is the first study to evaluate the efficacy of acupuncture in the treatment of FSD using the female sexual function index scale from 6 dimensions. The second advantage is that the method used (ie, the nonpharmacological method) is simple, readily available, highly safe with few side effects, and relatively inexpensive with high patient satisfaction. However, limitations include small sample size and lack of further detailed grouping, pre and post control study of patients, blank control group, and pre and post control study of sex hormones.

Conclusion

Acupuncture can effectively treat FSD from all dimensions with high safety, good satisfaction, and definite curative effect, and thus, it is worthy of promotion and application.

Zhang JT, Ma L, Gong X, et al. Clinical Study on the Use of Acupuncture for the Treatment of Female Sexual Dysfunction: A Pilot Study. Sex Med 2022;10:100541.

The neurobiology of bremelanotide for the treatment of hypoactive sexual desire disorder in premenopausal women

Hypoactive sexual desire disorder (HSDD) is a common female sexual dysfunction and is estimated to affect approximately 10% of women in the United States. It has been suggested that HSDD is associated with an imbalance of hormone and neurotransmitter levels in the brain, resulting in decreased excitation, increased inhibition, or a combination of both. Evidence suggests neurotransmitters, including dopamine (DA), norepinephrine, and serotonin, as well as hormones such as estradiol and testosterone, contribute to female sexual desire and response. Current treatments for HSDD include psychotherapy, and two US Food and Drug Administration-approved medications for premenopausal women: flibanserin, a serotonin mixed agonist and antagonist, and bremelanotide, a melanocortin receptor (MCR) agonist. Melanocortins are endogenous neuropeptides associated with the excitatory pathway of the female sexual response system. MCRs are found throughout the body, including the brain. Bremelanotide is an MCR agonist that nonselectively activates several of the receptor subtypes, of which subtype 4 (MC4R) is the most relevant at therapeutic doses. MC4R is predominantly expressed in the medial preoptic area (mPOA) of the hypothalamus in the brain, and is important for female sexual function. Animal studies suggest that bremelanotide may affect female sexual desire by activating presynaptic MC4Rs on neurons in the mPOA of the hypothalamus, leading to increased release of DA, an excitatory neurotransmitter that increases sexual desire. This review presents what is known about the mechanism of action of bremelanotide in the context of treating HSDD.

The Neurobiology of Behavior and Its Applicability for Animal Welfare: A Review

Simple Summary

Animal welfare is the result of physical and psychological well-being and is expected to occur if animals are free: (1) from hunger, thirst and malnutrition, (2) from discomfort, (3) from pain, (4) to express normal behavior, and (5) from fear and distress. Nevertheless, well-being is not a constant state but rather the result of certain brain dynamics underlying innate motivated behaviors and learned responses. Thus, by understanding the foundations of the neurobiology of behavior we fathom how emotions and well-being occur in the brain. Herein, we discuss the potential applicability of this approach for animal welfare. First, we provide a general view of the basic responses coordinated by the central nervous system from the processing of internal and external stimuli. Then, we discuss how those stimuli mediate activity in seven neurobiological systems that evoke innate emotional and behavioral responses that directly influence well-being and biological fitness. Finally, we discuss the basic mechanisms of learning and how it affects motivated responses and welfare.

Abstract

Understanding the foundations of the neurobiology of behavior and well-being can help us better achieve animal welfare. Behavior is the expression of several physiological, endocrine, motor and emotional responses that are coordinated by the central nervous system from the processing of internal and external stimuli. In mammals, seven basic emotional systems have been described that when activated by the right stimuli evoke positive or negative innate responses that evolved to facilitate biological fitness. This review describes the process of how those neurobiological systems can directly influence animal welfare. We also describe examples of the interaction between primary (innate) and secondary (learned) processes that influence behavior.

Randomized Controlled Phase II Evaluation of Two Dose Levels of Bupropion Versus Placebo for Sexual Desire in Female Cancer Survivors: NRG-CC004

PURPOSE

Because of the negative impact of cancer treatment on female sexual function, effective treatments are warranted. The purpose of this multisite study was to evaluate the ability of two dose levels of extended-release bupropion, a dopaminergic agent, to improve sexual desire more than placebo at 9 weeks, measured by the desire subscale of the Female Sexual Function Index (FSFI), and to evaluate associated toxicities.

METHODS

Postmenopausal women diagnosed with breast or gynecologic cancer and low baseline FSFI desire scores (< 3.3), who had completed definitive cancer therapy, were eligible. Women were randomly assigned to receive 150 mg or 300 mg once daily of extended-release bupropion or a matching placebo. t-tests were performed on the FSFI desire subscale to evaluate whether there was a significantly greater change from baseline to 9 weeks between placebo and each bupropion arm as the primary end point. Sixty-two patients per arm provided 80% power using a one-sided t-test.

RESULTS

Two hundred thirty women were randomly assigned from 72 institutions through the NRG Oncology NCORP network. At 9 weeks, there were no statistically significant differences in change of the desire subscale scores between groups; participants in all three arms reported improvement. The mean changes for each arm were placebo 0.62 (standard deviation [SD] = 1.18), 150-mg once daily bupropion 0.64 (SD = 0.95), and 300-mg once daily bupropion 0.60 (SD = 0.89). Total and subscale scores on the FSFI were low throughout the study, indicating dysfunction in all groups.

CONCLUSION

Bupropion was not more effective than placebo in improving the desire subscale of the FSFI. Subscale and total scores of the FSFI demonstrated dysfunction throughout the 9 weeks of the study. More research is needed to support sexual function in female cancer survivors.

Cyperus esculentus L. and Tetracarpidium conophorum Müll. Arg. Supplemented Diet Improved Testosterone Levels, Modulated Ectonucleotidases and Adenosine Deaminase Activities in Platelets from L-NAME-Stressed Rats

In hypertensive individuals, platelet morphology and function have been discovered to be altered, and this has been linked to the development of vascular disease, including erectile dysfunction (ED). The impact of nutritional supplementation with Cyperus esculentus (tiger nut, TN) and Tetracarpidium conophorum (walnut, WN) on androgen levels, ectonucleotidases, and adenosine deaminase (ADA) activities in platelets from L-NAME (Nω-nitro-L-arginine methyl ester hydrochloride) challenged rats were investigated. We hypothesized that these nuts may show a protective effect on platelets aggregation and possibly enhance the sex hormones, thereby reverting vasoconstriction. Wistar rats (male; 250-300 g; n = 10) were grouped into seven groups as follows: basal diet control group (I); basal diet/L-NAME/Viagra (5 mg/kg/day) as positive control group (II); ED-induced group (basal diet/L-NAME) (III); diet supplemented processed TN (20%)/L-NAME (IV); diet supplemented raw TN (20%)/L-NAME (V); diet supplemented processed WN (20%)/L-NAME (VI); and diet supplemented raw WN (20%)/L-NAME (VII). The rats were given their regular diet for 2 weeks prior to actually receiving L-NAME (40 mg/kg/day) for ten days to induce hypertension. Platelet androgen levels, ectonucleotidases, and ADA were all measured. L-NAME considerably lowers testosterone levels (54.5 ± 2.2; p < 0.05). Supplementing the TN and WN diets revealed improved testosterone levels as compared to the control (306.7 ± 5.7), but luteinizing hormone levels remained unchanged. Compared to control groups, the L-NAME-treated group showed a rise in ATP (127.5%) hydrolysis and ADA (116.7%) activity, and also a decrease in ADP (76%) and AMP (45%) hydrolysis. Both TN and WN supplemented diets resulted in substantial (p < 0.05) reversal effects. Enhanced testosterone levels and modulation of the purinergic system in platelets by TN and WN could be one of the mechanisms by which they aid in vasoconstriction control.

Hypothalamic cellular and molecular plasticity linked to sexual experience in male rats and mice

Male sexual behavior is subject to learning, resulting in increased efficiency of experienced males compared to naive ones. The improvement in behavioral parameters is underpinned by cellular and molecular changes in the neural circuit controlling sexual behavior, particularly in the hypothalamic medial preoptic area. This review provides an update on the mechanisms related to the sexual experience in male rodents, emphasizing the differences between rats and mice.

Effects of Sleep Deprivation by Olfactorily Induced Sexual Arousal Compared to Immobilization Stress and Manual Sleep Deprivation on Neuromessengers and Time Keeping Genes in the Suprachiasmatic Nuclei and Other Cerebral Entities of Syrian Hamsters-An Immunohistochemical Study

We investigated the effects of sexual arousal induced by olfactory stimuli on the expression of neuromodulators, neurotransmitters and sexual steroid receptors in the suprachiasmatic nucleus (SCN, the circadian pacemaker of mammals) and other cerebral entities of Syrian hamsters (Mesocricetus auratus) compared to manual sleep deprivation and immobilization stress. The hamsters kept under a 12:12 hours (h) light:dark cycle were deprived of sleep by sexual stimulation, gentle manual handling or immobilization stress for 1 h at the beginning of the light phase and subsequently sacrificed at zeitgeber time 01:00, respectively; for comparison, hamsters were manually sleep deprived for 6 or 20 h or sacrificed after completing a full sleep phase. As demonstrated by immunohistochemistry, apart from various alterations after manual sleep deprivation, sexual stimulation caused down-regulation of arginine-vasopressin (AVP), vasointestinal peptide (VIP), serotonin (5-HT), substance P (SP), and met-enkephalin (ME) in the SCN. Somatostatin (SOM) was diminished in the medial periventricular nucleus (MPVN). In contrast, an increase in AVP was observed in the PVN, that of oxytocin (OXY) in the supraoptic nucleus (SON), of tyrosine-hydroxylase (TH) in the infundibular nucleus (IN), and dopamine beta-hydroxylase (DBH) in the A7 neuron population of the brain stem (A7), respectively. Testosterone in plasma was increased. The results indicate that sexual arousal extensively influences the neuropeptide systems of the SCN, suggesting an involvement of the SCN in reproductive behavior.

Quercetin enhances sexual behavior and improves ectonucleotidases activity in the hypothalamus of rats treated with cyclosporine

In order to confirm the erectile potential of Quercetin (Q) in cyclosporine-induced hypertensive rats, this research assesses the influence of Q on the ectonucleotidases and adenosine deaminase (ADA) in the brains of rats. Male Wistar rats (200 g-250 g) were divided into five groups at random: Normal control (CTRL), cyclosporine-induced hypertensive rats (25 mg kg day-1 ) (HT) group, positive control (Sildenafil [SIL], 5 mg kg day-1 ), Quercetin 25 mg kg day-1 (25 Q), and Quercetin 50 mg kg day-1 (50 Q). Aside from standard diet-fed male rats; cyclosporine was given i.p for the period of 30 days as well as Q orally while the female rats were only given a standard diet. The animals were subjected to sexual activity (copulation) after which the male rat hypothalamus was dissected for biochemical examination (E-NTPDase activities, ecto-5'-nucleotidase as well as ADA and also levels of nitric oxide [NO]). We observed that Q enhanced copulatory behavior as evident in mounting, intromission, ejaculation numbers, and latencies. A substantial (p < .05) increase in the activity of E-NTPDase (ATP and ADP as substrate) without any notable difference in the action of ecto-5' nucleotidase was facilitated by cyclosporine-induction when compared to the CTRL. The 50 mg/kg, however, had the highest reversal effect in accordance with dose manner. Also, cyclosporine increased ADA activity with a concomitant reduction of NO level while both doses of Q down-regulated ADA activity and, increased NO levels. Enhanced sexual behavior, modulation of ectonucleotidases as well as ADA activity and increased NO levels suggest that Q-rich plant foods may be promising sources of dietary phytonutrients for erectile dysfunction (ED) management. PRACTICAL APPLICATIONS: Behavioral and biochemical assays evaluated showed that Q significantly enhanced sexual behavior as well as improved ATP bioavailability in cyclosporine-induced erectile dysfunctional rats. The modulatory effects of Q on ectonucleotidases, along with its ability to minimize adenosine deaminase activity and increase nitric oxide levels, indicate that Q-rich plants and/or plant foods may be promising sources of dietary phytonutrients for erectile dysfunction management.

Association of erectile dysfunction with tinnitus: a nationwide population-based study

With many previous studies indicating a higher prevalence of sexual problems in patients with tinnitus, the association between tinnitus and erectile dysfunction (ED) has become an interesting topic that warrants further research. In our study, we hypothesized that tinnitus may be associated with ED and aimed to further explore the relationship between these two medical conditions using a nationwide population-based database. After retrieving data of 19,329 patients with ED and 19,329 propensity score-matched patients without ED (controls) from Taiwan’s National Health Insurance Dataset, we defined the diagnosis date (the date of the first ED claim) for patients with ED as the index date for cases, and the date of the first utilization of ambulatory care by patients without ED during the index year of their matched case as the index date for controls. We found that 1247 out of 38,658 sampled patients (3.23%) had received a tinnitus diagnosis within the year before the index date, with 792 (4.10%) from cases and 455 (2.35%) from controls. We then utilized multiple logistic regression analysis and observed that cases were more likely to have had a prior tinnitus diagnosis compared to controls (OR 1.772; 95% CI 1.577–1.992; p < 0.001). Lastly, we adjusted the data for co-morbid medical disorders and social economic factors, with the end results showing that cases were more likely than controls to have a prior diagnosis of tinnitus (OR 1.779, 95% CI 1.582–2.001, p < 0.001). Through our investigation, we have ultimately detected a novel association between ED and tinnitus and urge physicians to be alert to the possibility of the development of ED in patients treated for tinnitus.

Microbiota-gut-brain axis as a regulator of reward processes

Our gut harbours trillions of microorganisms essential for the maintenance of homeostasis and host physiology in health and disease. In the last decade, there has been a growing interest in understanding the bidirectional pathway of communication between our microbiota and the central nervous system. With regard to reward processes there is accumulating evidence from both animal and human studies that this axis may be a key factor in gating reward valence. Focusing on the mesocorticolimbic pathway, we will discuss how the intestinal microbiota is involved in regulating brain reward functions, both in natural (i.e. eating, social or sexual behaviours) and non-natural reinforcers (drug addiction behaviours including those relevant to alcohol, psychostimulants, opioids and cannabinoids). We will integrate preclinical and clinical evidence suggesting that the microbiota-gut-brain axis could be implicated in the development of disorders associated with alterations in the reward system and how it may be targeted as a promising therapeutic strategy. Cover Image for this issue: https://doi.org/10.1111/jnc.15065.

Shift Work Sleep Disorder and Night Shift Work Significantly Impair Erectile Function

OBJECTIVES

Here we examine the association between shift work sleep disorder (SWSD) and erectile dysfunction (ED) in shift workers.

METHODS

Men presenting to a single andrology clinic between January 2014 and July 2017 completed validated questionnaires: International Index of Erectile Function (IIEF), Patient Health Questionnaire-9 (PHQ-9), and the nonvalidated SWSD Questionnaire. Men were also asked about shift work schedule, comorbidities, phosphodiesterase 5 (PDE5) inhibitor use, and testosterone use. Serum total testosterone values were determined for each visit. Linear regression was performed controlling for testosterone use, testosterone levels, PDE5 inhibitor use, age, and comorbidities to determine the effect of SWSD on ED as assessed using the IIEF.

RESULTS

Of the 754 men completing questionnaires, 204 reported nonstandard shift work (begins before 7 am or after 6 pm, regularly extends out of that frame, or rotates frequently) and 48 were found to have SWSD using a screening questionnaire. Nonstandard shift work alone did not result in worse IIEF-EF scores (P = .31), but those who worked nonstandard shifts and had SWSD demonstrated IIEF-EF scores 2.8 points lower than men without SWSD (P < .01). When assessing for the type of shift work performed, men who worked night shifts had IIEF-EF scores 7.6 points lower than men who worked during the day or evening (P < .01). Testosterone use improved IIEF-EF scores for men with SWSD by 2.9 points, ameliorating the effect of SWSD on ED. However, baseline testosterone levels were not associated with worse erectile function in this cohort.

CONCLUSION

Men with SWSD have worse erectile function, with men who work night shifts having even poorer erectile function. These findings suggest that circadian rhythm disturbance may significantly impact erectile function. While testosterone therapy may partly reverse the effects of SWSD, shift work is a potential risk factor for ED and should be assessed for as part of the evaluation of men with ED. Rodriguez KM, Kohn TP, Kohn JR, et al. Shift Work Sleep Disorder and Night Shift Work Significantly Impair Erectile Function. J Sex Med 2020;17:1687-1693.

Sexual Behavior and Synaptic Plasticity

Although sex drive is present in many animal species, sexual behavior is not static and, like many other behaviors, can be modified by experience. This modification relies on synaptic plasticity, a sophisticated mechanism through which neurons change how they process a given stimulus, and the neurophysiological basis of learning. This review addresses the main plastic effects of steroid sex hormones in the central nervous system (CNS) and the effects of sexual experience on the CNS, including effects on neurogenesis, intracellular signaling, gene expression, and changes in dendritic spines, as well as behavioral changes.

Effects of N-nitro L-arginine methyl ester and α-tocopherol on testicular oxidative stress caused by exposure to cigarette smoke

Testis is a rich organ with blood vessels. For this reason, it is possible that the toxic substances of the cigarette carried in the blood change the balance between the oxidant and the antioxidant system in this organ. In this study, it was aimed to investigate the effects of N-nitro L-arginine methyl ester and α-tocopherol on testicular oxidative stress caused by exposure to cigarette smoke. 45 wistar male rats were used in the study. Five groups were formed: control, cigarette smoke, cigarette smoke + α-tocopherol, cigarette smoke + N-nitro L-arginine methyl ester and cigarette smoke + α-tocopherol + N-nitro L-arginine methyl ester. Biochemical and histological evaluations were performed to determine the damage caused by cigarette smoke. It was observed that there were structural and functional disturbances at the cellular and hormonal level in the smoking group. Biochemical evaluations showed that cellular damage was reduced in treatment groups. Histological examinations were revealed that the damage caused by cigarette smoke exposure was eliminated in treatment groups. As a result of our study, we think that oxidative damage and hormonal irregularity in the testes tissue caused by cigarette smoke exposure can be improved with α-tocopherol and N-nitro L-arginine methyl ester application.

Mixed Emotions: An Incentive Motivational Model of Sexual Deviance

Sexual offending behavior is a complex and multifaceted phenomenon. Most existing etiological models describe sexual offending behavior as a variant of offending behavior and mostly include factors referring to disinhibition and sexual deviance. In this article, we argue that there is additional value in describing sexual offending behavior as sexual behavior in terms of an incentive model of sexual motivation. The model describes sexual arousal as an emotion, triggered by a competent stimulus signaling potential reward, and comparable to other emotions coupled with strong bodily reactions. Consequently, we describe sexual offending behavior in terms of this new model with emphasis on the development of deviant sexual interests and preferences. Summarized, the model states that because sexual arousal itself is an emotion, there is a bidirectional relationship between sexual self-regulation and emotional self-regulation. Not only can sex be used to regulate emotional states (i.e., sexual coping), emotions can also be used, consciously or automatically, to regulate sexual arousal (i.e., sexual deviance). Preliminary support for the model is drawn from studies in the field of sex offender research as well as sexology and motivation research.

Direct in Vivo Electrochemical Detection of Resting Dopamine Using Poly(3,4-ethylenedioxythiophene)/Carbon Nanotube Functionalized Microelectrodes

Dopamine (DA) is a monoamine neurotransmitter responsible for the maintenance of a variety of vital life functions. In vivo DA signaling occurs over multiple time scales, from subsecond phasic release due to dopamine neuron firing to tonic release responsible for long-term DA concentration changes over minutes to hours. Due to the complex, multifaceted nature of DA signaling, analytical sensing technology must be capable of recording DA from multiple locations and over multiple time scales. Decades of research has focused on improving in vivo detection capabilities for subsecond phasic DA, but the accurate detection of absolute resting DA levels in real time has proven challenging. We have developed a poly(3,4-ethylenedioxythiophene) (PEDOT)-based nanocomposite coating that exhibits excellent DA sensing capabilities for resting DA. PEDOT/functionalized carbon nanotube (PEDOT/CNT)-coated carbon fiber microelectrodes (CFEs) are capable of directly measuring resting DA using square wave voltammetry (SWV) with high sensitivity and selectivity. Incorporation of a PEDOT/CNT coating significantly increases the sensitivity for the detection of resting DA by a factor of 422. SWV measurements performed at PEDOT/CNT-functionalized CFEs implanted in the rat dorsal striatum reveal the absolute basal DA concentration to be 82 ± 6 nM. Systemic administration of the dopamine transporter inhibitor nomifensine increases resting DA to a maximum 207 ± 16 nM at 28 ± 2 min following injection. PEDOT/CNT was also functionalized onto individual gold electrode sites along silicon microelectrode arrays (MEAs) to produce a multisite DA sensing electrode. MEA implantation allows for the quantification of basal DA from different brain regions with excellent spatial resolution. SWV detection paired with PEDOT/CNT functionalization is highly adaptable and shows great promise for tonic DA detection with high spatial and temporal resolution.

Endocannabinoids Interact With the Dopaminergic System to Increase Sexual Motivation: Lessons From the Sexual Satiety Phenomenon

In male rats, copulation to satiety induces a long-lasting sexual inhibitory state, considered to rely on a decreased sexual motivation. Dopaminergic transmission at the mesolimbic system plays a central role in the regulation of male sexual motivation. Endocannabinoids (eCBs) modulate the activity of the mesolimbic system and both dopamine (DA) and cannabinoid receptor activation reverses the sexual inhibition that characterizes sexually satiated rats. The eCB anandamide reverses sexual satiety when systemically administered or infused into the ventral tegmental area (VTA), the region where the activity of mesolimbic dopaminergic neurons is regulated. Thus, it could be thought that sexual motivation is diminished during the long-lasting sexual inhibition of sexually satiated rats and that eCBs reverse that inhibition through the modulation of the dopaminergic system. To test this hypothesis, we assessed the motivational state of sexually satiated male rats and determined if 2-arachidonoylglycerol (2-AG), the most abundant eCB and a full cannabinoid receptor agonist, also reversed the sexual inhibitory state. To establish the possible interaction between 2-AG and anandamide with the dopaminergic system for the reversal of sexual satiety, we analyzed the effects of the co-administration of each eCB and DA receptor agonists or antagonists. Results showed that 24-h after copulation to satiety, when the sexual inhibition is well established, the males’ sexual motivation is diminished as measured in the sexual incentive motivation test. 2-AG, similarly to anandamide, reverses sexual satiety through the activation of CB1 receptors and both eCBs interact with the dopaminergic system to reverse the sexual inhibitory state. 2-AG effects are mediated by the modulation of the D2-like DA receptor family, whereas anandamide’s effects are clearly mediated by the modulation of the D1-like DA receptor family and the activation of D2-like DA receptors. Present results evidence that a reduced sexual motivation underlies the sexual inhibitory state of sexually satiated rats and support the notion that eCBs reverse sexual satiety by modulating dopaminergic transmission, presumably at the mesolimbic system. Anandamide and 2-AG have a different interaction with D1-like and D2-like DA receptor families. Altogether present data endorse the association of the eCB system with the regulation of the motivational tone at the mesolimbic system.

Impact of body iron store on sexual function: a comprehensive review and pilot cohort study in midlife women

PURPOSE

Both iron deficiency (ID) and female sexual dysfunction (FSD) affect more than 25% of the world population. The aim of this study was to identify a connection between these two conditions based on the existing literature and to investigate this interrelation in a small pilot cross-sectional study.

METHODS

A database search for publications referring to ID and FSD was conducted. The resulting common denominators were used to formulate hypotheses regarding the interaction of these diseases. Simultaneously, 45 healthy middle-aged women completed questionnaires about their sexual function and provided a blood sample for the purpose of determining ferritin and haemoglobin levels. The main outcome measures included an analysis of responses to questions on sexuality and partnership and of blood ferritin and haemoglobin levels. The secondary outcomes included an assessment of further influences on libido, such as sex hormones, menopausal status, health, and life satisfaction.

RESULTS

Altered monoaminergic cerebral metabolism, hyperprolactinaemia and hypothyroidism, impaired socioemotional interaction, increased anxiety, and depression in both, ID and FSD, account for the most comprehensive explanations for the postulated association between the two conditions. Despite a feasible assumption, our empirical findings failed to demonstrate any correlation between ID and FSD. We identified a certain impact of menopausal hormonal status on sexual function.

CONCLUSION

ID has no influence on FSD in the given population, although the literature suggests that FSD may at least be partly due to ID. Further research seems justified given the potential advantages for sexual health, considering that ID is an easily treatable disease.

Brain Cortical and Hippocampal Dopamine: A New Mechanistic Approach for Eurycoma longifolia Well-Known Aphrodisiac Activity and Its Chemical Characterization

Eurycoma longifolia Jack (Fam.: Simaroubaceae), known as Tongkat Ali (TA), has been known as a symbol of virility and sexual power for men. Metabolic profiling of the aqueous extract of E. longifolia (AEEL) using UPLC-MS/MS in both positive and negative modes allowed the identification of seventeen metabolites. The identified compounds were classified into four groups: quassinoids, alkaloids, triterpenes, and biphenylneolignans. AEEL is considered safe with oral LD₅₀ cut-off >5000 mg/kg. Oral administration of 50, 100, 200, 400, or 800 mg/kg of AEEL for 10 consecutive days to Sprague-Dawley male rats caused significant reductions in mounting, intromission, and ejaculation latencies and increased penile erection index. AEEL increased total body weight and relative weights of seminal vesicles and prostate. Total and free serum testosterone and brain cortical and hippocampal dopamine content was significantly elevated in treated groups with no significant effects on serotonin or noradrenaline content.

Effect of a multi-ingredient based food supplement on sexual function in women with low sexual desire

Background

Studies have demonstrated that women with low desire and low excitement have negative feelings regarding their physical and emotional satisfaction, as well as their happiness. In this study, we evaluate the efficacy of Libicare® - a multi-ingredient food supplement - to improve sexual function in postmenopausal women.

Methods

This was an exploratory, prospective, non-controlled, observational study. Postmenopausal women aged 45–65 with a risk of sexual dysfunction (Female Sexual Function Index (FSFI) < 25.83) were included during routine clinical visits and treated with 2 tablets of Libicare® daily for 2 months. Libicare® is an oral food supplement containing Trigonella foenum graecum, Turnera diffusa, Tribulus terrestris, and Ginkgo biloba dry extracts. Primary endpoint: change vs. baseline in FSFI score. Secondary endpoints: 1) changes in testosterone and serum steroid levels of free testosterone and sex hormone-binding globulin (SHBG) levels and 2) tolerability.

Results

A total of 29 patients (mean age: 54.69 years) were included. FSFI mean (SD) score showed a significant increase: 20.15 (4.48) vs 25.03 (6.94), baseline vs final; p = 0.0011, paired t-test. Most patients (86.2%) increased their FSFI score. All FSFI domains, except dyspareunia, showed significant increases. The highest increase was observed in the desire domain (p = 0.0004). Testosterone and SHBG levels were assessed in 21 patients. A significant increase in testosterone level was observed: 0.41 (0.26) vs. 0.50 (0.34) pg/mL, baseline vs. final; p = 0.038, Wilcoxon test. 52.4% of patients increased their testosterone levels. Finally, a significant decrease was observed in SHBG level: 85 (32.9) vs. 73 (26.8) nmol/L, baseline vs. final; p = 0.0001; paired t-test. 95.2% of patients decreased their SHBG levels.

Conclusion

In this pilot study, a significant improvement in sexual function and related hormone levels was observed with Libicare®. Further studies must be conducted to confirm these exciting results.

Trial registration

Current Controlled Trial ISRCTN12928573. Date of registration: 28/March/2019. Retrospectively registered.

Why Do Birds Flock? A Role for Opioids in the Reinforcement of Gregarious Social Interactions

The formation of social groups provides safety and opportunities for individuals to develop and practice important social skills. However, joining a social group does not result in any form of obvious, immediate reinforcement (e.g., it does not result in immediate copulation or a food reward), and individuals often remain in social groups despite agonistic responses from conspecifics. Much is known about neural and endocrine mechanisms underlying the motivation to perform mate- or offspring-directed behaviors. In contrast, relatively little is known about mechanisms underlying affiliative behaviors outside of these primary reproductive contexts. Studies on flocking behavior in songbirds are beginning to fill this knowledge gap. Here we review behavioral evidence that supports the hypothesis that non-sexual affiliative, flocking behaviors are both (1) rewarded by positive social interactions with conspecifics, and (2) reinforced because affiliative contact reduces a negative affective state caused by social isolation. We provide evidence from studies in European starlings, Sturnus vulgaris, that mu opioid receptors in the medial preoptic nucleus (mPOA) play a central role in both reward and the reduction of a negative affective state induced by social interactions in flocks, and discuss potential roles for nonapeptide/opioid interactions and steroid hormones. Finally, we develop the case that non-sexual affiliative social behaviors may be modified by two complementary output pathways from mPOA, with a projection from mPOA to the periaqueductal gray integrating information during social interactions that reduces negative affect and a projection from mPOA to the ventral tegmental area integrating information leading to social approach and reward.

Tadalafil Preserves Penile Nitric Oxide Synthase from Detrimental Effect of Paroxetine in Rats

Objective

Paroxetine is a commonly prescribed SSRI that can impair erectile function in animal models via inhibition of nitric oxide synthase (NOS). Tadalafil potentiates nitric oxide (NO)-mediated responses in isolated trabecular smooth muscle and penile erection. The purpose of this study was to evaluate the impact of co-administering tadalafil with paroxetine on penile NOS levels in rats.

Materials and Methods

A total of 30 male Sprague-Dawley rats were divided into 3 groups as control (Group-C), paroxetine (Group-P) and paroxetine plus tadalafil (Group-P+T). After 28 days of treatment, rats were sacrificed and their penile tissues were harvested for analysis. NOS isoform protein levels and immunoreactivity scores of NOS were assessed. Statistical significance level was set at p<0.05.

Results

Neuronal NOS (nNOS) levels were significantly decreased in group-P, compared with group-C (p<0.001). In comparison, rats in group-P+T had significantly higher nNOS levels compared to group-P (p<0.001). Endothelial NOS (eNOS) and inducible NOS (iNOS) levels were significantly higher in group-P compared with group-C (p<0.01). The levels of eNOS and iNOS in group-P+T were similar to group-C.

Conclusion

Daily treatment with tadalafil prevented chronic paroxetine-induced changes in all three NOS isoform levels. Tadalafil treatment may therefore be a useful therapy in men with paroxetine-associated erectile dysfunction.

A critical role for Dop1-mediated dopaminergic signaling in the plasticity of behavioral and neuronal responses to sex pheromone in a moth

Most animal species, including insects, are able to modulate their responses to sexual chemosignals and this flexibility originates from the remodeling of olfactory areas under the influence of dopaminergic system. In the moth Agrotis ipsilon, the behavioral response of males to the female-emitted sex pheromone increases throughout adult life and after a prior exposure to pheromone signal and this change is accompanied by an increase in neuronal sensitivity within the primary olfactory centers, the antennal lobes (ALs). To identify the underlying neuromodulatory mechanisms, we examined whether this age- and experience-dependent olfactory plasticity is mediated by dopamine (DA) through the Dop1 receptor, an ortholog of the vertebrate D1-type dopamine receptors, which is positively coupled to adenylyl cyclase. We cloned A. ipsilon Dop1 (AiDop1) which is expressed predominantly in brain and especially in ALs and its knockdown induced decreased AL cAMP amounts and altered sex pheromone-orientated flight. The levels of DA, AiDop1 expression and cAMP in ALs increased from the third day of adult life and at 24h and 48h following pre-exposure to sex pheromone and the dynamic of these changes correlated with the increased responsiveness to sex pheromone. These results demonstrate that Dop1 is required for the display of male sexual behavior and that age- and experience-related neuronal and behavioral changes are sustained by DA-Dop1 signaling that operates within ALs probably through cAMP-dependent mechanisms in A. ipsilon. Thus, this study expands our understanding of the neuromodulatory mechanisms underlying olfactory plasticity, mechanisms that appear to be highly conserved between insects and mammals.

The maternal hormone in the male brain: Sexually dimorphic distribution of prolactin signalling in the mouse brain

Research of the central actions of prolactin is highly focused on females, but this hormone has also documented roles in male physiology and behaviour. Here, we provide the first description of the pattern of prolactin-derived signalling in the male mouse brain, employing the immunostaining of phosphorylated signal transducer and activator of transcription 5 (pSTAT5) after exogenous prolactin administration. Next, we explore possible sexually dimorphic differences by comparing pSTAT5 immunoreactivity in prolactin-supplemented males and females. We also assess the role of testosterone in the regulation of central prolactin signalling in males by comparing intact with castrated prolactin-supplemented males. Prolactin-supplemented males displayed a widespread pattern of pSTAT5 immunoreactivity, restricted to brain centres showing expression of the prolactin receptor. Immunoreactivity for pSTAT5 was present in several nuclei of the preoptic, anterior and tuberal hypothalamus, as well as in the septofimbrial nucleus or posterodorsal medial amygdala of the telencephalon. Conversely, non-supplemented control males were virtually devoid of pSTAT5-immunoreactivity, suggesting that central prolactin actions in males are limited to situations concurrent with substantial hypophyseal prolactin release (e.g. stress or mating). Furthermore, comparison of prolactin-supplemented males and females revealed a significant, female-biased sexual dimorphism, supporting the view that prolactin has a preeminent role in female physiology and behaviour. Finally, in males, castration significantly reduced pSTAT5 immunoreactivity in some structures, including the paraventricular and ventromedial hypothalamic nuclei and the septofimbrial region, thus indicating a region-specific regulatory role of testosterone over central prolactin signalling.

Leaf-Methanolic Extract of Pseudopanax arboreus (Araliaceae) (L. F. Phillipson) Reverses Amitriptyline-Induced Sexual Dysfunction in Male Rats

The people of the Bayangi tribe (Manyu Division) of Cameroon have used the leaves of Pseudopanax arboreus (Araliaceae) traditionally for decades as an aphrodisiac. In order to scientifically investigate this folk claim, we evaluated the effects of the leaf-aqueous extract of P. arboreus on the sexual behavior of normal male rats. The present study was designed to assess the effects of the leaf-methanolic extract of P. arboreus on amitriptyline-induced sexual dysfunction in male rats. Sexually impaired male rats were randomly divided into 4 groups of 8 rats each. Group 1 received 10 ml/kg distilled water, while group 2 was given 6 mg/kg Viagra. Groups 3 and 4 received 46.5 and 93 mg/kg of the leaf-methanolic extract, respectively. Female rats were made receptive by ovariectomy and subsequent hormonal treatment. Sexual behavior parameters were monitored on days 1, 7, 14, and 21 by pairing each male to a receptive female. The extract-treated rats registered significant decrease in mount latency (ML) and intromission latency (IL); nonsignificant increase in mount frequency (MF), intromission frequency (IF), and penile licking (PL); significant decrease in postejaculatory interval (PEI); contrasting effects in ejaculation latency (EL); and mean intromission interval (MII). Both doses of the extract also provoked a significant increase in relative weight of testes, but had no significant effect on the plasma hormonal profile. These findings are similar to those obtained with normal male rats and show that the leaf-methanolic extract of P. arboreus could constitute a potential solution to male sexual impairment.

Neural circuits regulating sexual behaviors via the olfactory system in mice

Reproduction is essential for any animal species. Reproductive behaviors, or sexual behaviors, are largely shaped by external sensory cues exchanged during sexual interaction. In many animals, including rodents, olfactory cues play a critical role in regulating sexual behavior. What exactly these olfactory cues are and how they impact animal behavior have been a central question in the field. Over the past few decades, many studies have dedicated to identifying an active compound that elicits sexual behavior from crude olfactory components. The identified substance has served as a tool to dissect the sensory processing mechanisms in the olfactory systems. In addition, recent advances in genetic engineering, and optics and microscopic techniques have greatly expanded our knowledge of the neural mechanisms underlying the control of sexual behavior in mice. This review summarizes our current knowledge about how sexual behaviors are controlled by olfactory cues.

The Modulating Role of Sex and Anabolic-Androgenic Steroid Hormones in Cannabinoid Sensitivity

Cannabis is the most commonly used illicit drug worldwide. Although its use is associated with multiple adverse health effects, including the risk of developing addiction, recreational and medical cannabis use is being increasing legalized. In addition, use of synthetic cannabinoid drugs is gaining considerable popularity and is associated with mass poisonings and occasional deaths. Delineating factors involved in cannabis use and addiction therefore becomes increasingly important. Similarly to other drugs of abuse, the prevalence of cannabis use and addiction differs remarkably between males and females, suggesting that sex plays a role in regulating cannabinoid sensitivity. Although it remains unclear how sex may affect the initiation and maintenance of cannabis use in humans, animal studies strongly suggest that endogenous sex hormones modulate cannabinoid sensitivity. In addition, synthetic anabolic-androgenic steroids alter substance use and further support the importance of sex steroids in controlling drug sensitivity. The recent discovery that pregnenolone, the precursor of all steroid hormones, controls cannabinoid receptor activation corroborates the link between steroid hormones and the endocannabinoid system. This article reviews the literature regarding the influence of endogenous and synthetic steroid hormones on the endocannabinoid system and cannabinoid action.

Rats selectively bred for showing divergent behavioral traits in response to stress or novelty or spontaneous yawning with a divergent frequency show similar changes in sexual behavior: the role of dopamine

Sexual behavior plays a fundamental role for reproduction in mammals and other animal species. It is characterized by an anticipatory and a consummatory phase, and several copulatory parameters have been identified in each phase, mainly in rats. Sexual behavior varies significantly across rats even when they are of the same strain and reared under identical conditions. This review shows that rats of the same strain selectively bred for showing a divergent behavioral trait when exposed to stress or novelty (i.e. Roman high and low avoidance rats, bred for their different avoidance response to the shuttle box, and high and low novelty exploration responders rats, bred for their different exploratory response to a novel environment) or a spontaneous behavior with divergent frequency (i.e. low and high yawning frequency rats, bred for their divergent yawning frequency) show similar differences in sexual behavior, mainly in copulatory pattern, but also in sexual motivation. As shown by behavioral pharmacology and intracerebral microdialysis experiments carried out mainly in Roman rats, these sexual differences may be due to a more robust dopaminergic tone present in the mesocorticolimbic dopaminergic system of one of the two sub-lines (e.g. high avoidance, high novelty exploration, and low yawning rat sub-lines). Thus, differences in genotype and/or in prenatal/postnatal environment lead not only to individual differences in temperament and environmental/emotional reactivity but also in sexual behavior. Because of the highly conserved mechanisms controlling reproduction in mammals, this may occur not only in rats but also in humans.

Effects of Treatment with Nauclea latifolia Root Decoction on Sexual Behavior and Reproductive Functions in Male Rabbits

Nauclea latifolia is used in traditional medicine for the treatment of male reproductive diseases. Despite its vast uses, its effects on the male reproductive system have not been scientifically proven. This study aimed to investigate the effects of Nauclea latifolia root decoction on sexual behavior and functions in male rabbits. Twenty-four male rabbits were divided into four groups: The first group received daily distilled water orally. The second, third, and fourth groups were orally treated with 100, 200, and 400 mg/kg body weight of Nuclea latifolia root, respectively. Sexual behavior parameters were carried out on weeks 1, 2, and 3 of the study. Testosterone, follicle-stimulating hormone (FSH), and luteinizing hormone (LH) were measured from the serum, while the testes tissue samples were used for antioxidant and histopathological examinations. Treatment with 200 and 400 mg/kg body weight resulted in significantly (p < .05) increased frequencies of mounting and intromission. In addition, the ejaculation latency was significantly prolonged (p < .05). The latencies of mounting and intromission were significantly decreased (p < .05), whereas ejaculation frequency increased. Serum testosterone, FSH, and LH increased significantly (p < .05) after treatment with Nuclea latifolia. There was an increase in epididymal sperm counts at 200 and 400 mg/kg body weight doses compared to the control. The extract also increased sperm motility and viability and improved testicular oxidative status. Histological examination revealed an increase in germinal layer thickness. The present study suggests that treatment with N. latifolia improves male sexual function and fertility and protects the testes from oxidative damage.

The role of ΔfosB in the medial preoptic area: Differential effects of mating and cocaine history

The transcription factor deltaFosB (ΔFosB) is induced in the nucleus accumbens (NAc) by repeated exposure to drugs of abuse and natural rewards. Less is known about its role in other brain areas. Here, we compared the effects of mating versus cocaine history on induction of ΔFosB in the medial preoptic area (MPOA), an integral site for reproductive behavior, and in the NAc. ΔFosB immunoreactivity (ir) was increased in the MPOA of previously naïve and experienced male rats that mated the day before euthanasia, compared to unmated controls and experienced males with recent mating abstinence. Western immunoblots confirmed that the 35-37-kDa isoform of ΔFosB was increased more in recently mated males. Conversely, previous plus recent cocaine did not increase ΔFosB-ir in the MPOA, despite an increase in the NAc. Next, a viral vector expressing ΔFosB, its dominant negative antagonist ΔJunD, or green fluorescent protein (GFP) control, were microinjected bilaterally into the MPOA. ΔFosB overexpression impaired copulation and promoted female-directed aggression, compared to ΔJunD and control males. These data suggest that ΔFosB in the mPOA is expressed in an experience-dependent manner and affects systems that coordinate mating and aggression. (PsycINFO Database Record

Dopamine, Noradrenaline and Differences in Sexual Behavior between Roman High and Low Avoidance Male Rats: A Microdialysis Study in the Medial Prefrontal Cortex

Roman High- (RHA) and Low-Avoidance (RLA) outbred rats, which differ for a respectively rapid vs. poor acquisition of the active avoidance response in the shuttle-box, display differences in sexual activity when put in the presence of a sexually receptive female rat. Indeed RHA rats show higher levels of sexual motivation and copulatory performance than RLA rats, which persist also after repeated sexual activity. These differences have been correlated to a higher tone of the mesolimbic dopaminergic system of RHA rats vs. RLA rats, revealed by the higher increase of dopamine found in the dialysate obtained from the nucleus accumbens of RHA than RLA rats during sexual activity. This work shows that extracellular dopamine and noradrenaline (NA) also, increase in the dialysate from the medial prefrontal cortex (mPFC) of male RHA and RLA rats put in the presence of an inaccessible female rat and more markedly during direct sexual interaction. Such increases in dopamine (and its main metabolite 3,4-dihydroxyphenylacetic acid, DOPAC) and NA were found in both sexually naïve and experienced animals, but they were higher: (i) in RHA than in RLA rats; and (ii) in sexually experienced RHA and RLA rats than in their naïve counterparts. Finally, the differences in dopamine and NA in the mPFC occurred concomitantly to those in sexual activity, as RHA rats displayed higher levels of sexual motivation and copulatory performance than RLA rats in both the sexually naïve and experienced conditions. These results suggest that a higher dopaminergic tone also occurs in the mPFC, together with an increased noradrenergic tone, which may be involved in the different copulatory patterns found in RHA and RLA rats, as suggested for the mesolimbic dopaminergic system.

Hypercaloric diet prevents sexual impairment induced by maternal food restriction

Prenatal undernutrition impairs copulatory behavior and increases the tendency to become obese/overweight, which also reduces sexual behavior. Re-feeding rats prenatally undernourished with a normocaloric diet can restore their physiological conditions and copulatory behavior. Thus, the present study investigated whether a hypercaloric diet that is administered in rats during the juvenile period prevents sexual impairments that are caused by maternal food restriction and the tendency to become overweight/obese. Female rats were prenatally fed a 40% restricted diet from gestational day 2 to 18. The pups received a hypercaloric diet from postnatal day (PND) 23 to PND65 (food restricted hypercaloric [FRH] group) or laboratory chow (food restricted control [FRC] group). Pups from non-food-restricted dams received laboratory chow during the entire experiment (non-food-restricted [NFR] group). During the juvenile period and adulthood, body weight gain was evaluated weekly. The day of balanopreputial separation, sexual behavior, sexual organ weight, hypodermal adiposity, striatal dopamine and serotonin, serum testosterone, and tumor necrosis factor α (TNF-α) were evaluated. The FRH group exhibited an increase in body weight on PND58 and PND65. The FRC group exhibited an increase in the latency to the first mount and intromission and an increase in serum TNF-α levels but a reduction of dopaminergic activity. The hypercaloric diet reversed all of these effects but increased adiposity. We concluded that the hypercaloric diet administered during the juvenile period attenuated reproductive impairments that were induced by maternal food restriction through increases in the energy expenditure but not the tendency to become overweight/obese.

Enhanced dopamine detection sensitivity by PEDOT/graphene oxide coating on in vivo carbon fiber electrodes

Dopamine (DA) is a monoamine neurotransmitter responsible for regulating a variety of vital life functions. In vivo detection of DA poses a challenge due to the low concentration and high speed of physiological signaling. Fast scan cyclic voltammetry at carbon fiber microelectrodes (CFEs) is an effective method to monitor real-time in vivo DA signaling, however the sensitivity is somewhat limited. Electrodeposition of poly(3,4-ethylene dioxythiophene) (PEDOT)/graphene oxide (GO) onto the CFE surface is shown to increase the sensitivity and lower the limit of detection for DA compared to bare CFEs. Thicker PEDOT/GO coatings demonstrate higher sensitivities for DA, but display the negative drawback of slow adsorption and electron transfer kinetics. The moderate thickness resulting from 25 s electrodeposition of PEDOT/GO produces the optimal electrode, exhibiting an 880% increase in sensitivity, a 50% decrease in limit of detection and minimally altered electrode kinetics. PEDOT/GO coated electrodes rapidly and robustly detect DA, both in solution and in the rat dorsal striatum. This increase in DA sensitivity is likely due to increasing the electrode surface area with a PEDOT/GO coating and improved adsorption of DA's oxidation product (DA-o-quinone). Increasing DA sensitivity without compromising electrode kinetics is expected to significantly improve our understanding of the DA function in vivo.

Endocannabinoid system in sexual motivational processes: Is it a novel therapeutic horizon?

The endocannabinoid system (ECS), which is composed of the cannabinoid receptors types 1 and 2 (CB1 and CB2) for marijuana's psychoactive ingredient Δ⁹-tetrahydrocannabinol (Δ⁹-THC), the endogenous ligands (AEA and 2-AG) and the enzymatic systems involved in their biosynthesis and degradation, recently emerged as important modulator of emotional and non-emotional behaviors. For centuries, in addition to its recreational actions, several contradictory claims regarding the effects of Cannabis use in sexual functioning and behavior (e.g. aphrodisiac vs anti-aphrodisiac) of both sexes have been accumulated. The identification of Δ⁹-THC and later on, the discovery of the ECS have opened a potential therapeutic target for sexual dysfunctions, given the partial efficacy of current pharmacological treatment. In agreement with the bidirectional modulation induced by cannabinoids on several behavioral responses, the endogenous cannabinoid AEA elicited biphasic effects on sexual behavior as well. The present article reviews current available knowledge on herbal, synthetic and endogenous cannabinoids with respect to the modulation of several aspects of sexuality in preclinical and human studies, highlighting their therapeutic potential.

Effects of Sex Steroids in the Human Brain

Sex steroids are thought to play a critical developmental role in shaping both cortical and subcortical structures in the human brain. Periods of profound changes in sex steroids invariably coincide with the onset of sex differences in mental health vulnerability, highlighting the importance of sex steroids in determining sexual differentiation of the brain. Yet, most of the evidence for the central effects of sex steroids relies on non-human studies, as several challenges have limited our understanding of these effects in humans: the lack of systematic assessment of the human sex steroid metabolome, the different developmental trajectories of specific sex steroids, the impact of genetic variation and epigenetic changes, and the plethora of interactions between sex steroids, sex chromosomes, neurotransmitters, and other hormonal systems. Here we review how multimodal strategies may be employed to bridge the gap between the basic and clinical understanding of sex steroid-related changes in the human brain.

Changes in Sexual Behavior of Orchidectomized Rats Under Influence of Allotransplantation of Testicular Interstitial Cell Suspension

Transplantation of hormone-producing cells is an experimental endocrine dysfunction treatment. The present study investigated the effects of orchidectomy (OE) and transplantation of interstitial cell suspension (ICS) on rat sexual behavior. Adult experimental animals were divided into two populations. One of these populations had sexual experience before the experiment and the other did not. Each population was divided into three groups: control group and two orchidectomized groups. One of the orchidectomized groups was treated with ICS, and the other was treated with the vehicle. The changes in the sexual behavior were investigated on the following parameters: mount latency (ML), intromission latency (IL), ejaculation latency (EL), mount frequency (MF), intromission frequency (IF), copulatory efficacy (CE), and IF/EL ratio. The investigation of these changes lasted 4 weeks after ICS transplantation. The parameters of sexual behavior reflected a decrease in sexual function after OE at the beginning of the observation, especially for the animals that did not have a sexual experience. However, it was shown that sexual activity increased in the following 4 weeks. We have indicated that the loss of gonads attenuated the capacity to acquire sexual experience; nonetheless, it did not mean that the animals completely lost this capacity. Transplantation of ICS facilitated the maintenance of male sexual behavior after OE, fractionally enlarged the size of regressed seminal vesicles of the animals, and increased the free testosterone (T) level. These findings suggest the ICS can be considered as a temporal source of androgens, which can facilitate a restoration of sexual activity.