Pharmacological analysis of male rat sexual behavior

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.

Cocaine Effects on Reproductive Behavior and Fertility: An Overview

Cocaine is one of the most widely used drugs that, due to its molecular properties, causes various behavioral alterations, including sexual behavior. In vivo and in vitro studies conducted mainly in mammals have shown various disorders of sexual activity and morpho-functional dysfunctions of the gonads in both sexes. Although the modalities are still unclear, cocaine has been shown to alter the cell cycle, induce apoptosis, and alter sperm motility. In females, this drug alters the formation of the meiotic spindle as well as may obstruct the ovulation mechanism of mature oocytes. The data provided in this review, in addition to reviewing the current literature on the main effects of cocaine on spermatogenesis and oogenesis mainly in mammals, will hopefully provide a basic overview that may help and support further future studies on the molecular interaction of cocaine and its metabolites with germ cells.

Effect of Selective Dorsal Neurectomy on Erectile Function in Rats

OBJECTIVE

This study aimed to investigate the effect of penile selective dorsal neurectomy (SDN) on erectile function in rats.

METHODS

Twelve adult male Sprague-Dawley rats (15 weeks old) were divided into three groups (n=4 per group): in control group, rats received no treatment; in sham group, rats underwent a sham operation; in SDN group, rats underwent SDN with half of the dorsal penile nerve severed. The mating test was performed, and the intracavernous pressure (ICP) assessed six weeks after the surgical treatment.

RESULTS

At postoperative six weeks, the mating test revealed no significant difference in mounting latency and mounting frequency among the three groups (P>0.05), while the ejaculation latency (EL) was significantly longer and ejaculation frequency (EF) lower in the SDN group than in the control and sham groups (P<0.05). There were no significant differences in preoperative and postoperative ICP and ICP/mean arterial blood pressure (MAP) among the three groups (P>0.05).

CONCLUSION

SDN does not adversely affect the erectile function and sexual desire of rats, and at the same time it can reduce EL and EF, providing an application basis for SDN in the clinical treatment of premature ejaculation.

The influence of manual semen collection in male trained dogs (Canis familiaris), in the presence or absence of a female in estrus, on the concentrations of cortisol, oxytocin, prolactin and testosterone

Sex pheromones are chemical substances secreted into the environment that affect the physiology and behavior of recipients. Females use these compounds during oestrus to attract males, which leads to attempts of mating. This study evaluates the influence of manual semen collection in male dogs, in the presence or absence of a female in estrus, on the blood concentrations of cortisol (CRT), oxytocin (OXT), prolactin (PRL) and testosterone (T), as hormones involved both in the physiology of reproduction and stress. Ten male dogs were used in Experiment 1 to measure the serum and plasma concentrations of the aforementioned hormones in the absence of semen collection. Subsequently in the same animals, the concentrations of these hormones were evaluated before and after semen collection in the presence (Exp. 2) or in absence of a female in estrus (Exp. 3). No significant changes in hormone concentration caused by the semen collection were found, either with, or without the presence of female in estrus. Obtained results suggest that the procedure of manual semen collection in dogs, probably due to its passive character, does not stimulate endocrine glands to secrete hormones, and the process of ejaculation is probably controlled by neural pathway. The lack of effect of semiochemical stimulation to the CRT, PRL, OXT and T level, could be caused by a short contact with female during semen collection. Further studies on involvement of the hormones during the process of natural mating, especially preceded by long courtships, similar to that observed under natural conditions, should shed a light on the physiology of mating and the connection between the endocrine system and semiochemical stimulation in dogs.

Flexibility of neural circuits regulating mating behaviors in mice and flies

Mating is essential for the reproduction of animal species. As mating behaviors are high-risk and energy-consuming processes, it is critical for animals to make adaptive mating decisions. This includes not only finding a suitable mate, but also adapting mating behaviors to the animal's needs and environmental conditions. Internal needs include physical states (e.g., hunger) and emotional states (e.g., fear), while external conditions include both social cues (e.g., the existence of predators or rivals) and non-social factors (e.g., food availability). With recent advances in behavioral neuroscience, we are now beginning to understand the neural basis of mating behaviors, particularly in genetic model organisms such as mice and flies. However, how internal and external factors are integrated by the nervous system to enable adaptive mating-related decision-making in a state- and context-dependent manner is less well understood. In this article, we review recent knowledge regarding the neural basis of flexible mating behaviors from studies of flies and mice. By contrasting the knowledge derived from these two evolutionarily distant model organisms, we discuss potential conserved and divergent neural mechanisms involved in the control of flexible mating behaviors in invertebrate and vertebrate brains.

Oxytocin via oxytocin receptor excites neurons in the endopiriform nucleus of juvenile mice

The neuropeptide oxytocin (OXT) modulates social behaviors across species and may play a developmental role for these behaviors and their mediating neural pathways. Despite having high, stable levels of OXT receptor (OXTR) ligand binding from birth, endopiriform nucleus (EPN) remains understudied. EPN integrates olfactory and gustatory input and has reciprocal connections with several limbic areas. Because the role of OXTR signaling in EPN is unknown, we sought to provide anatomical and electrophysiological information about OXTR signaling in mouse EPN neurons. Using in situ hybridization, we found that most EPN neurons co-express Oxtr mRNA and the marker for VGLUT1, a marker for glutamatergic cells. Based on high levels of OXTR ligand binding in EPN, we hypothesized that oxytocin application would modulate activity in these cells as measured by whole-cell patch-clamp electrophysiology. Bath application of OXT and an OXTR specific ligand (TGOT) increased the excitability of EPN neurons in wild-type, but not in OXTR-knockout (KO) tissue. These results show an effect of OXT on a mainly VGLUT1+ cell population within EPN. Given the robust, relatively stable OXTR expression in EPN throughout life, OXTR in this multi-sensory and limbic integration area may be important for modulating activity in response to an array of social or other salient stimuli throughout the lifespan and warrants further study.

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.

Sexual incentive motivation, sexual behavior, and general arousal: Do rats and humans tell the same story?

Sexual incentive stimuli activate sexual motivation and heighten the level of general arousal. The sexual motive may induce the individual to approach the incentive, and eventually to initiate sexual acts. Both approach and the ensuing copulatory interaction further enhance general arousal. We present data from rodents and humans in support of these assertions. We then suggest that orgasm is experienced when the combined level of excitation surpasses a threshold. In order to analyze the neurobiological bases of sexual motivation, we employ the concept of a central motive state. We then discuss the mechanisms involved in the long- and short-term control of that state as well as those mediating the momentaneous actions of sexual incentive stimuli. This leads to an analysis of the neurobiology behind the interindividual differences in responsivity of the sexual central motive state. Knowledge is still fragmentary, and many contradictory observations have been made. Nevertheless, we conclude that the basic mechanisms of sexual motivation and the role of general arousal are similar in rodents and humans.

Erectile Function and Sexual Behavior: A Review of the Role of Nitric Oxide in the Central Nervous System

Nitric oxide (NO), the neuromodulator/neurotransmitter formed from l-arginine by neuronal, endothelial and inducible NO synthases, is involved in numerous functions across the body, from the control of arterial blood pressure to penile erection, and at central level from energy homeostasis regulation to memory, learning and sexual behavior. The aim of this work is to review earlier studies showing that NO plays a role in erectile function and sexual behavior in the hypothalamus and its paraventricular nucleus and the medial preoptic area, and integrate these findings with those of recent studies on this matter. This revisitation shows that NO influences erectile function and sexual behavior in males and females by acting not only in the paraventricular nucleus and medial preoptic area but also in extrahypothalamic brain areas, often with different mechanisms. Most importantly, since these areas are strictly interconnected with the paraventricular nucleus and medial preoptic area, send to and receive neural projections from the spinal cord, in which sexual communication between brain and genital apparatus takes place, this review reveals that central NO participates in concert with neurotransmitters/neuropeptides to a neural circuit controlling both the consummatory (penile erection, copulation, lordosis) and appetitive components (sexual motivation, arousal, reward) of sexual behavior.

Oxytocin, Erectile Function and Sexual Behavior: Last Discoveries and Possible Advances

A continuously increasing amount of research shows that oxytocin is involved in numerous central functions. Among the functions in which oxytocin is thought to be involved are those that play a role in social and sexual behaviors, and the involvement of central oxytocin in erectile function and sexual behavior was indeed one of the first to be discovered in laboratory animals in the 1980s. The first part of this review summarizes the results of studies done in laboratory animals that support a facilitatory role of oxytocin in male and female sexual behavior and reveal mechanisms through which this ancient neuropeptide participates in concert with other neurotransmitters and neuropeptides in this complex function, which is fundamental for the species reproduction. The second part summarizes the results of studies done mainly with intranasal oxytocin in men and women with the aim to translate the results found in laboratory animals to humans. Unexpectedly, the results of these studies do not appear to confirm the facilitatory role of oxytocin found in male and female sexual behavior in animals, both in men and women. Possible explanations for the failure of oxytocin to improve sexual behavior in men and women and strategies to attempt to overcome this impasse are considered.

Hypothalamic dopamine neurons motivate mating through persistent cAMP signalling

Transient neuromodulation can have long-lasting effects on neural circuits and motivational states^1-4. Here we examine the dopaminergic mechanisms that underlie mating drive and its persistence in male mice. Brief investigation of females primes a male's interest to mate for tens of minutes, whereas a single successful mating triggers satiety that gradually recovers over days⁵. We found that both processes are controlled by specialized anteroventral and preoptic periventricular (AVPV/PVpo) dopamine neurons in the hypothalamus. During the investigation of females, dopamine is transiently released in the medial preoptic area (MPOA)-an area that is critical for mating behaviours. Optogenetic stimulation of AVPV/PVpo dopamine axons in the MPOA recapitulates the priming effect of exposure to a female. Using optical and molecular methods for tracking and manipulating intracellular signalling, we show that this priming effect emerges from the accumulation of mating-related dopamine signals in the MPOA through the accrual of cyclic adenosine monophosphate levels and protein kinase A activity. Dopamine transients in the MPOA are abolished after a successful mating, which is likely to ensure abstinence. Consistent with this idea, the inhibition of AVPV/PVpo dopamine neurons selectively demotivates mating, whereas stimulating these neurons restores the motivation to mate after sexual satiety. We therefore conclude that the accumulation or suppression of signals from specialized dopamine neurons regulates mating behaviours across minutes and days.

Three-Dimensional Proteome-Wide Scale Screening for the 5-Alpha Reductase Inhibitor Finasteride: Identification of a Novel Off-Target

Finasteride, a 5-alpha reductase (5α-R) inhibitor, is a widely used drug for treating androgen-dependent conditions. However, its use is associated with sexual, psychological, and physical complaints, suggesting that other mechanisms, in addition to 5α-R inhibition, may be involved. Here, a multidisciplinary approach has been used to identify potential finasteride off-target proteins. SPILLO-PBSS software suggests an additional inhibitory activity of finasteride on phenylethanolamine N-methyltransferase (PNMT), the limiting enzyme in formation of the stress hormone epinephrine. The interaction of finasteride with PNMT was supported by docking and molecular dynamics analysis and by in vitro assay, confirming the inhibitory nature of the binding. Finally, this inhibition was also confirmed in an in vivo rat model. Literature data indicate that PNMT activity perturbation may be correlated with sexual and psychological side effects. Therefore, results here obtained suggest that the binding of finasteride to PNMT might have a role in producing the side effects exerted by finasteride treatment.

Development and evaluation of aphrodisiac potential of a classical ayurvedic formulation, 'Kaamdev ghrita' in rat model

BACKGROUND

Ghee is widely considered as the Indian name for clarified butterfat and processing of ghee with therapeutic herbs i.e. ghrita is renowned for augmenting their medicinal properties. Kaamdev ghrita (also known as 'VajikaranaRasayana') is cow ghee based classical Ayurvedic formulation from the aphrodisiac category, which is used to ameliorate and potentiate sexual performance and also in the treatment of sexual dysfunctions, infertility, and premature ejaculation.

OBJECTIVE

Present research work deals with the organoleptic, physicochemical, and biological assessment of Kaamdev ghrita for its aphrodisiac activity using in-vivo animal models.

MATERIAL AND METHODS

Kaamdev ghrita was prepared using Indian cow's ghee as per standard Ayurvedic classical texts and subjected to organoleptic (color, odor, taste, texture, touch), physicochemical (acid value, peroxide value, iodine value, saponification value, unsaponifiable matter, extractive values, refractive index, and specific gravity) analyses as per the standard pharmacopeial procedures. The aphrodisiac potential of ghrita in rat model was evaluated by monitoring sexual behavioral performance using different parameters (mount frequency and latency, intromission frequency and latency, anogenital grooming and sniffing) at the dose of 150 and 300 mg/kg body weight.

RESULTS

The physicochemical evaluation of Kaamdev ghrita showed higher acid value, iodine value, refractive index, and specific gravity whereas the lower saponification and peroxide value than the plain ghee. Kaamdev ghrita revealed the presence of flavonoids, alkaloids, saponins, sterols, terpenoids, coumarins, tannins, and showed remarkable antioxidant activity by in-vitro assays. It augmented the sexual performance in a dose-dependent manner as indicated by significant improvement (P < 0.05) in mount frequency and latency, intromission frequency and latency, anogenital grooming, and sniffing as compared to plain ghee treated control group. The present investigation has corroborated the ethnopharmacological claim of Kaamdevghrita for its aphrodisiac potential.

CONCLUSION

Kaamdev ghrita exhibited aphrodisiac activity which may be attributed to the presence of antioxidant herbs present in it. It is the first scientific report on validation of the traditional claim of Kaamdev ghrita for its aphrodisiac potential.

Evaluation of the in Vivo Aphrodisiac Activity of a Cyclotide Extract from Hybanthus enneaspermus

Hybanthus enneaspermus is an Indian folk medicinal herb that has been widely used as a libido enhancer. This plant belongs to the Violaceae plant family, which ubiquitously contains disulfide-rich cyclic peptides named cyclotides. Cyclotides are an expanding plant-derived peptide family with numerous interesting bioactivities, and their unusual stability against proteolysis has attracted much attention in drug design applications. Recently, H. enneaspermus has been reported to be a rich source of cyclotides, and hence, it was of interest to investigate whether cyclotides contribute to its aphrodisiac activity. In this study, we evaluated the in vivo aphrodisiac activity of the herbal powder, extract, and the most abundant cyclotide, hyen D, extracted from H. enneaspermus on rats in a single dose regimen. After dosing, the sexual behaviors of male rats were observed, recorded, analyzed, and compared with those of the vehicle group. The results show that the extract and hyen D significantly decreased the intromission latency of sexually naïve male rats and the extract improved a range of other measured sexual parameters. The results suggest that the extract could enhance libido as well as facilitate erectile function in male rats and that the cyclotide hyen D could contribute to the libido-enhancing activity of this ethnomedicinal herb.

Social Stimuli Induce Activation of Oxytocin Neurons Within the Paraventricular Nucleus of the Hypothalamus to Promote Social Behavior in Male Mice

Oxytocin (OT) is critical for the expression of social behavior across a wide array of species; however, the role of this system in the encoding of socially relevant information is not well understood. In the present study, we show that chemogenetic activation of OT neurons within the paraventricular nucleus of the hypothalamus (PVH) of male mice (OT-Ires-Cre) enhanced social investigation during a social choice test, while chemogenetic inhibition of these neurons abolished typical social preferences. These data suggest that activation of the OT system is necessary to direct behavior preferentially toward social stimuli. To determine whether the presence of a social stimulus is sufficient to induce activation of PVH-OT neurons, we performed the first definitive recording of OT neurons in awake mice using two-photon calcium imaging. These recordings demonstrate that social stimuli activate PVH-OT neurons and that these neurons differentially encode social and nonsocial stimuli, suggesting that PVH-OT neurons may act to convey social salience of environmental stimuli. Finally, an attenuation of social salience is associated with social disorders, such as autism. We therefore also examined possible OT system dysfunction in a mouse model of autism, Shank3b knock-out (KO) mice. Male Shank3b KO mice showed a marked reduction in PVH-OT neuron number and administration of an OT receptor agonist improved social deficits. Overall, these data suggest that the presence of a social stimulus induces activation of the PVH-OT neurons to promote adaptive social behavior responses.SIGNIFICANCE STATEMENT Although the oxytocin (OT) system is well known to regulate a diverse array of social behaviors, the mechanism in which OT acts to promote the appropriate social response is poorly understood. One hypothesis is that the presence of social conspecifics activates the OT system to generate an adaptive social response. Here, we selectively recorded from OT neurons in the paraventricular hypothalamic nucleus (PVH) to show that social stimulus exposure indeed induces activation of the OT system. We also show that activation of the OT system is necessary to promote social behavior and that mice with abnormal social behavior have reduced numbers of PVH-OT neurons. Finally, aberrant social behavior in these mice was rescued by administration of an OT receptor agonist.

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.

Evaluation of the aphrodisiac potential of a chemically characterized aqueous extract of Tamarindus indica pulp

ETHNOPHARMACOLOGICAL RELEVANCE

Tamarindus indica is an ingredient in the traditional aphrodisiac formulations in Africa and India. It is also a widely used food ingredient in other tropical countries.

AIM OF THE STUDY

The present study was aimed to evaluate the aphrodisiac potential and reproductive safety profile of aqueous extract of Tamarindus indica in male Wistar rats.

MATERIALS AND METHODS

The aqueous extract was prepared by maceration of pulp followed by reduction of volume in rotavapor under heat followed by freeze drying. The prepared extract was characterized for contents of total phenol, flavonoid, and saponin. It was also subjected to phytoconstituent analysis using GCMS. Further, the extract was evaluated for acute toxicity study. The aphrodisiac and reproductive toxicity potential were evaluated in animals after grouping them in four with six animals each namely, normal control, standard (Sildenafil citrate, 4mg/kg p.o.) and extract of Tamarindus indica treated groups at two dose levels, 125 and 250mg/kg p.o. The study was conducted for 54 days with daily once dosing of extract and standard. Equal number of females was grouped without treatment for evaluation of parameters of sexual desire (mount frequency and intromission frequency) and parameters of sexual arousal (mount latency and intromission latency). These parameters were evaluated on day 14, 28, 42 and 54. Animals were sacrificed on day 54, testes were removed and studied for histopathological changes.

RESULTS

The extract showed 6.6mg gallic acid equivalent/g of total phenol, 2.3mg catechin equivalent/g of flavonoid and 11.6% saponin. Forty chemical constituents were identified by GCMS analysis. In acute toxicity study, the extract was found to be safe till 2000mg/kg p.o. Efficacy study showed significant (p<0.05) improvement in parameters of sexual desire (mount frequency and intromission frequency) and parameters of sexual arousal on all observed days except mount frequency for 125mg/kg on 42nd day and intromission frequency for both doses of tamarind compared to normal control. Improvements in these parameters were comparable to the standard drug. Histopathology study and sperm count suggested an increase in sperm production without any sign of toxicity in testis. Sperm motility significantly (p<0.05) increased in the treatment groups that received extract at 250mg/kg compared to normal control.

CONCLUSION

Aqueous extract of Tamarindus indica possessed aphrodisiac activity together with spermatogenic potential.

ICV galanin-like peptide stimulates non-contact erections but not touch-based erections in adult, sexually experienced male rats

Galanin-like peptide (GALP) is a neuropeptide transcribed only within the arcuate nucleus of the hypothalamus and is thought to be a mediator between energetics and reproductive function. Intracerebroventricular (ICV) injection of GALP is known to have effects on feeding, and to significantly increase gonadotropin releasing hormone- (GnRH-) mediated luteinizing hormone (LH) secretion. Furthermore, ICV GALP is known to stimulate fos production in the medial pre-optic area (mPOA) and to a lesser extent, the paraventricular nucleus (PVN). ICV injection of 5.0nmol GALP profoundly stimulates male rat sexual behavior. It is not known if GALP's effects on sex behavior are due to an increase in appetitive or mechanical (erectile) aspects of male sexual behavior. To determine this, sexually experienced male rats were cannulated in the lateral ventricle and injected with 5.0nmol GALP or vehicle. Immediately after injections, male rats were placed in an arena connected to a second arena via a tube with a fan. The second arena contained a steroid-primed female and her bedding. The male rat had olfactory but not visual or tactile contact with the female. We analyzed the amount of time the male rats spent investigating the air intake and the number of non-contact erections (NCEs) in a 30minute test. ICV GALP significantly (p<0.05) increased both the amount of time of olfactory investigations and NCEs compared to vehicle. In a second set of animals, we tested if ICV GALP could stimulate touch-based erections. GALP had no significant effect on touch-based erections compared to vehicle. These data suggest that GALP's activation of fos within the mPOA is indicative of its action to stimulate the appetitive aspects of male sexual behavior.

Aphrodisiac Activity of the Aqueous Crude Extract of Purple Corn ( Zea mays) in Male Rats

In the present study, the aphrodisiac properties of the purple corn (Zea mays) in male rats were analyzed. The aqueous crude extract of purple corn (at 25, 50, and 75 mg/kg) was administered to (a) copulating male rats and (b) anesthetized and spinal cord transected male rats. Behavioral parameters of copulatory behavior and parameters of the genital motor pattern of ejaculation previous to its inhibition, under the influence of the purple corn extract, are described. Administration of the aqueous crude extract of purple corn significantly facilitates the arousal and execution of male rat sexual behavior without significant influences on the ambulatory behavior. In addition, purple corn extract elicit a significant increase in the number of discharges of the ejaculatory motor patterns and in the total number of genital motor patterns evoked in spinal rats. The present findings show that the aqueous crude extract of purple corn possesses aphrodisiac activity.

Neuroanatomical dichotomy of sexual behaviors in rodents: a special emphasis on brain serotonin

Much of the social behavior in which rodents engage is related to reproduction, such as maintaining a breeding territory, seeking mates, mating, and caring for their young. Rodents belong to the internally fertilizing species that require sexual behavior for reproduction. The dyadic, heterosexual patterns of most mammalian species are sexually dimorphic, but they also share mutual components in both sexes: sexual attraction is reciprocal, sexual initiative is assumed, appetitive behavior is engaged in, and mating involves consummatory and postconsummatory phases in females as well as in males. Serotonin, a phylogenetically ancient molecule, is the most widely distributed neurotransmitter in the brain and its signaling pathways are essential for numerous functions including sexual behavior. Since the late 1960s, brain serotonergic neurotransmission has been considered to exert an inhibitory influence on the neural mechanisms mediating sexual behavior. This contention was based mainly on the observations that a decrease in central serotonergic activity facilitated the elicitation of sexual behavior, whereas an increase in central serotonergic activity attenuated it. However, the discovery of over 14 types of serotonin receptors has added numerous layers of complexity to the study of serotonin and sexual behavior. Evidence shows that, upon activation, certain receptor subtypes facilitate, whereas some others suppress, sexual behavior, as well as sexual arousal and motivation. Furthermore, the role of these receptors has been shown to be different in the male and female sexes. The use of serotonergic pharmacological interventions, mouse strains with genetic polymorphisms causing alterations in the levels of brain serotonin, and animal models with genetic manipulations of various serotonin effectors has helped delineate the fundamental role of this neurotransmitter in the regulation of sexual behavior. This review aims to examine the basics of the components of female and male sexual behavior and the participation of the serotonin system in the modulation of these behaviors, with emphasis on rodents.

Anatomy and physiology of genital organs - men

Male sexual functions involve a number of organs and structures in genitalia whose role is to produce fertilizing gametes and to allow female-partner insemination. The testes belong to the reproductive and endocrine systems as they synthesize spermatozoa and androgens, and are under finely regulated hormonal control by the hypothalamopituitary axis. Sexual responses are controlled by a complex and coordinated interplay of both the somatic and the autonomic nervous system in multiple components of the brain, spinal cord, and relevant peripheral organs. Erectile bodies are an essential element of the penis and engorgement of the penis with blood leads to penile tumescence. Blood engorgement is due to relaxation of smooth-muscle cells of erectile tissue and endothelium of the penile arteries. The penis gains additional rigidity when the ischiocavernosus muscles contract. Stimuli from peripheral and/or central origins activate particular spinal nuclei, causing penile erection. Ejaculation consists of two phases, emission and expulsion, which correspond, respectively, to secretion of the different components of the semen by sex glands and forceful expulsion of semen due to rhythmic contractions of the bulbospongiosus muscle. A spinal generator of ejaculation integrates genital stimuli and sexual cues and, when the excitatory threshold is reached, triggers ejaculation by orchestrating the activation of autonomic and somatic pathways commanding the peripheral events of ejaculation.

Genetic determinants of selective serotonin reuptake inhibitor related sexual dysfunction

Sexual dysfunction is a troubling obstacle for individuals being treated for depression and can be caused by both depressive symptoms as well as antidepressant drugs. Selective serotonin reuptake inhibitors (SSRIs) represent a class of antidepressants commonly associated with sexual dysfunction, even after symptomatic improvement. Candidate gene studies have identified associations between sexual dysfunction and altered SSRI pharmacokinetics or to the neurotransmitter systems affected by depression and SSRI treatment. The multifactorial nature of this phenotype and study heterogeneity are currently limitations to the translation of these findings to clinical use. Larger, prospective studies of genetic-guided antidepressant selection may help to clarify the clinical utility of pharmacogenetics in minimizing sexual side effects.

Review: neuroestrogen regulation of socio-sexual behavior of males

It is thought that estrogen (neuroestrogen) synthesized by the action of aromatase in the brain from testosterone activates male socio-sexual behaviors, such as aggression and sexual behavior in birds. We recently found that gonadotropin-inhibitory hormone (GnIH), a hypothalamic neuropeptide, inhibits socio-sexual behaviors of male quail by directly activating aromatase and increasing neuroestrogen synthesis in the preoptic area (POA). The POA is thought to be the most critical site of aromatization and neuroestrogen action for the regulation of socio-sexual behavior of male birds. We concluded that GnIH inhibits socio-sexual behaviors of male quail by increasing neuroestrogen concentration beyond its optimal concentration in the brain for expression of socio-sexual behavior. On the other hand, it has been reported that dopamine and glutamate, which stimulate male socio-sexual behavior in birds and mammals, inhibit the activity of aromatase in the POA. Multiple studies also report that the activity of aromatase or neuroestrogen is negatively correlated with changes in male socio-sexual behavior in fish, birds, and mammals including humans. Here, we review previous studies that investigated the role of neuroestrogen in the regulation of male socio-sexual behavior and reconsider the hypothesis that neuroestrogen activates male socio-sexual behavior in vertebrates. It is considered that basal concentration of neuroestrogen is required for the maintenance of male socio-sexual behavior but higher concentration of neuroestrogen may inhibit male socio-sexual behavior.

Clinical neuroanatomy and neurotransmitter-mediated regulation of penile erection

Erectile dysfunction (ED) has an adverse impact on men's quality of life. Penile erection, which is regulated by nerves that are innervated into the erectile tissue, can be affected by functional or anatomical trauma of the perineal region, including specific structures of the penis, causing ED. Penile erection is neurologically controlled by the autonomic nervous system. Therefore, it is of utmost importance to understand the neurogenic structure of the erectile tissue and the types of neurotransmitters involved in the penile erection process. Here, we highlight the basic clinical anatomy and erectile function of the penis. Understanding the clinical connotation of the relationship between penile erectile structure and function may provide fresh insights for identifying the main mechanisms involved in ED and help develop surgical techniques for the treatment of ED.

Role of acetylcholine in control of sexual behavior of male and female mammals

The results of studies using systemic or central applications of cholinergic drugs suggest that acetylcholine makes important contributions to the neurochemical control of male- and female-typical reproductive behaviors. In males, cholinergic control seems largely specific to some elements or aspects of copulatory behavior that can vary significantly across species. Synapses in or near the medial preoptic area represent part of this mechanism, but the entire system appears to extend more widely, perhaps especially to one or more structures flanking some part of the lateral ventricle. In females, the lordosis response that essentially defines sexual receptivity is clearly responsive to cholinergic drugs. The same seems likely to be true of other elements of female sexual behavior, but additional studies will be needed to confirm this. Changes in cholinergic activity may help to mediate estrogenic effects on female sexual behavior. However, estrogen exposure can increase or decrease cholinergic effects, suggesting a relationship that is complex and requires further analysis. Also presently unclear is the localization of the cholinergic effects on female sexual responses. Though periventricular sites again have been implicated, their identity is presently unknown. This review discusses these and other aspects of the central cholinergic systems affecting male and female sexual behaviors.

A rare symptom in posttraumatic stress disorder: Spontaneous ejaculation

Patient: Male, 25

Final Diagnosis: Post Traumatic Stress Disorder

Symptoms: Insomnia • nightmares • spontaneous ejaculation

Medication: Paroxentine

Clinical Procedure: —

Specialty: Psychiatry

Testosterone levels and sexual function disorders in depressive female patients: effects of antidepressant treatment

INTRODUCTION

Women suffer from depression more frequently than men, which indicates that sex hormones might be involved in the etiology of this disease.

AIMS

The purpose of this study was to assess the relationship between testosterone and depression pathophysiology in depressive women along with sexual function. We also investigated whether antidepressant treatment causes any change in levels of this hormone or in sexual function.

METHODS

Premenopausal female patients aged 25-46 years (n = 52) with diagnosed major depression were included in this study as the patient group, and 25- to 46-year-old premenopausal women without depression (n = 30) were included as the control group.

MAIN OUTCOME MEASURES

Serum testosterone and sex hormone-binding globulin (SHBG) levels were measured twice, before and after the antidepressant treatment. Bioavailable testosterone (cBT) levels were calculated using the assay results for total testosterone (TT), SHBG, and albumin according to the formulas of Vermeulen et al. Depression severity was measured using the 17-item Hamilton Depression Rating Scale, and sexual function was evaluated with the Arizona Sexual Experience Scale.

RESULTS

The mean TT and cBT levels significantly increased in the patient group after the antidepressant treatment (P < 0.001). Pre-treatment TT and cBT levels were significantly lower in the patient group than in the control group (P < 0.001). Similar results were obtained for post-treatment serum TT and cBT levels in the patient and control groups (P > 0.05). There were no significant differences among the groups in terms of SHBG level.

CONCLUSION

The low testosterone levels in depressed women compared with women in the control group and the elevated levels post-pharmacotherapy suggest that testosterone may be involved in depression.

Neuropeptides and central control of sexual behaviour from the past to the present: a review

Of the numerous neuropeptides identified in the central nervous system, only a few are involved in the control of sexual behaviour. Among these, the most studied are oxytocin, adrenocorticotropin, α-melanocyte stimulating hormone and opioid peptides. While opioid peptides inhibit sexual performance, the others facilitate sexual behaviour in most of the species studied so far (rats, mice, monkeys and humans). However, evidence for a sexual role of gonadotropin-releasing hormone, corticotropin releasing factor, neuropeptide Y, galanin and galanin-like peptide, cholecystokinin, substance P, vasoactive intestinal peptide, vasopressin, angiotensin II, hypocretins/orexins and VGF-derived peptides are also available. Corticotropin releasing factor, neuropeptide Y, cholecystokinin, vasopressin and angiotensin II inhibit, while substance P, vasoactive intestinal peptide, hypocretins/orexins and some VGF-derived peptide facilitate sexual behaviour. Neuropeptides influence sexual behaviour by acting mainly in the hypothalamic nuclei (i.e., lateral hypothalamus, paraventricular nucleus, ventromedial nucleus, arcuate nucleus), in the medial preoptic area and in the spinal cord. However, it is often unclear whether neuropeptides influence the anticipatory phase (sexual arousal and/or motivation) or the consummatory phase (performance) of sexual behaviour, except in a few cases (e.g., opioid peptides and oxytocin). Unfortunately, scarce information has been added in the last 15 years on the neural mechanisms by which neuropeptides influence sexual behaviour, most studied neuropeptides apart. This may be due to a decreased interest of researchers on neuropeptides and sexual behaviour or on sexual behaviour in general. Such a decrease may be related to the discovery of orally effective, locally acting type V phosphodiesterase inhibitors for the therapy of erectile dysfunction.

The effect of amantadine on clomipramine induced sexual dysfunction in male rats

OBJECTIVE

Several studies have reported that Clomipramine has the ability to suppress male rat sexual behavior. Literature indicates that the activation of brain D(2) receptors causes facilitation of penile erection, and a number of reports have indicated dopamine's involvement in sexual function. Hence this study was undertaken to investigate the effect of Amantadine, a dopamine agonists on the Clomipramine induced sexual dysfunction.

METHODS

The study subjects involved a total of 48 males and 48 females, 4 months old Sprague-Dawley albino rats, all housed in a group of six males and females separately in plexi glass cages in an acclimatized colony room (25±0.5(0)C) maintained on a 12/12 hr light/dark cycle. The male rats were randomly divided into four groups of 12 male rats each. Group I served as controls. Group II, III, and IV were treated with Amantadine (9 mg/kg body weight, p.o) 30 min, prior to the treatment with 13.5 mg/kg, 27 mg/Kg and 54 mg/Kg bodyweight p.o of Clomipramine respectively for 60 days. The control group received vehicle 1 ml / kg p.o. The sexual behavior of the male rats was observed to determine the following parameters: mount latency, intromission latency, ejaculation latency, post ejaculatory pause, and intromission frequency. As well as the sexual behavior; serum testosterone and histopathology of the testes were also investigated in this study.

RESULTS

The results indicate that Amantadine in all aspects failed to antagonize Clomipramine induced sexual dysfunction in male rats. Even the sexual competence of male rats treated with ½ therapeutic dose (TD) of Clomipramine failed to regain their sexual competence in the presence of Amantadine. Testicular damage and decline in testosterone levels continued in the presence of Amantadine.

CONCLUSION

Overall, the results suggest that Amantadine could not be a safe antidote to antagonize Clomipramine induced sexual dysfunction.

Spilanthes acmella ethanolic flower extract: LC-MS alkylamide profiling and its effects on sexual behavior in male rats

According to Indian Systems of Medicine, Spilanthes acmella (L.) Murr. (Family - Asteraceae), is considered effective in the treatment of sexual deficiencies especially due to ageing. In the present study, characterization of ethanolic extracts of the Spilanthes acmella flower and its effect on general mating pattern, penile erection and serum hormone levels of normal male Wistar albino rats were investigated and compared with sildenafil citrate. In vitro nitric oxide release was also investigated in human corpus cavernosum cell line. As N-alkylamides are a promising group, their profiling was performed using a gradient reversed phase high performance liquid chromatography/electrospray ionization ion trap mass spectrometry (HPLC/ESI-MS) method on an embedded polar column. MS(1) and MS(2) fragmentation data were used for identification purposes. For assessment of sexual behavior, animals were divided into five groups of eight male rats. The extracts (50, 100 and 150mg/kgbodyweight/day) and sildenafil citrate (5mg/kgbodyweight/day) (positive control) were administered orally for 28 days. The behavioral and sexual parameters were observed at days 0, 15, 28 and after a lapse of 7 and 14 days of discontinuance of drug treatment. Five N-isobutylamides, one 2-methylbutylamide and one 2-phenylethylamide were identified. The orally administered extract had a dose dependent positive effect on mounting frequency, intromission frequency and ejaculation frequency and the most significant effects (p<0.05) were observed at 150mg/kg treatment, even after a lapse of 7 and 14 days of discontinuance of drug treatment. A dose dependent effect was also observed on the FSH, LH and testosterone serum levels. With 150mg/kg of ethanolic extract the values for FSH, LH and testosterone were 3.10±0.25mlU/ml, 6.87±0.18mlU/ml and 3.72±0.12ng/ml, respectively. In vitro nitric oxide release was 21.7±2.9μM, which was significantly higher compared to the control group (p<0.01). Sildenafil citrate exhibited also a significant effect on NO release, but no effect on hormone levels of rats was observed. The aphrodisiac potential of an ethanolic Spilanthes acmella extract was demonstrated in vitro and in vivo. N-Alkylamides might attribute to the improved sexual potential. Study lends support to the traditional utilization of S. acmella as a sexual stimulating agent.

Nepeta cataria L. var. citriodora (Becker) increases penile erection in rats

ETHNOPHARMACOLOGICAL RELEVANCE

Nepeta cataria (NC), catnip, induces pleasure in cats and humans.

AIM OF THE STUDY

Because sexual behavior is involved in pleasure, the effect of NC on sexual behavior and penile erection was evaluated in male rats that were acutely fed chow enriched with 10% NC leaves. Further, yawning was monitored because we previously demonstrated that NC modifies dopaminergic-related behaviors and that sexual behavior is closely linked with the dopaminergic system. The general activity and the motor coordination were examined to investigate the possible motor and emotional interferences of the sexual performance.

MATERIAL AND METHODS

Male rats of the NC group received for a 4h period the chow enriched with 10% NC leaves while the control groups received regular chow. Fifteen min after the end of the 4h period of NC feeding the sexual behavior, apomorphine-induced penile erection and motor coordination were observed; the general activity in the open field was assessed 0, 15, 30 and 60 min after treatment.

RESULTS

NC treatment increased male rat's penile erection. A slightly facilitation on male rat sexual behavior and a decreased in general activity of NC treated rats were observed. No effects on motor coordination and yawning episodes were detected by the NC treatment.

CONCLUSIONS

It was suggested that NC increases penile erection and slightly improves male rat sexual behavior by an action on dopaminergic systems.

Mechanisms of penile erection and basis for pharmacological treatment of erectile dysfunction

Erection is basically a spinal reflex that can be initiated by recruitment of penile afferents, both autonomic and somatic, and supraspinal influences from visual, olfactory, and imaginary stimuli. Several central transmitters are involved in the erectile control. Dopamine, acetylcholine, nitric oxide (NO), and peptides, such as oxytocin and adrenocorticotropin/α-melanocyte-stimulating hormone, have a facilitatory role, whereas serotonin may be either facilitatory or inhibitory, and enkephalins are inhibitory. The balance between contractant and relaxant factors controls the degree of contraction of the smooth muscle of the corpora cavernosa (CC) and determines the functional state of the penis. Noradrenaline contracts both CC and penile vessels via stimulation of α₁-adrenoceptors. Neurogenic NO is considered the most important factor for relaxation of penile vessels and CC. The role of other mediators, released from nerves or endothelium, has not been definitely established. Erectile dysfunction (ED), defined as the "inability to achieve or maintain an erection adequate for sexual satisfaction," may have multiple causes and can be classified as psychogenic, vasculogenic or organic, neurologic, and endocrinologic. Many patients with ED respond well to the pharmacological treatments that are currently available, but there are still groups of patients in whom the response is unsatisfactory. The drugs used are able to substitute, partially or completely, the malfunctioning endogenous mechanisms that control penile erection. Most drugs have a direct action on penile tissue facilitating penile smooth muscle relaxation, including oral phosphodiesterase inhibitors and intracavernosal injections of prostaglandin E₁. Irrespective of the underlying cause, these drugs are effective in the majority of cases. Drugs with a central site of action have so far not been very successful. There is a need for therapeutic alternatives. This requires identification of new therapeutic targets and design of new approaches. Research in the field is expanding, and several promising new targets for future drugs have been identified.