Male Sexual Performance Research Articles

Pharmacological Features of Masculine Sexual Behavior in an Animal Model of Depression

BONILLA-JAIME, H., S. RETANA-MARQUEZ AND J. VELAZQUEZ-MOCTEZUMA. Pharmacological features of masculine sexual behavior in an animal model of depression. PHARMACOL BIOCHEM BEHAV 60(1) 39–45, 1998.—Neonatal treatment with clomipramine induces behavioral alterations during adulthood that resemble symptoms observed in human depression. Therefore, it has been proposed as an animal model of depression. Impairment of male sexual performance is one of the main effects of this treatment. Using this model of depression, we evaluated the effects of drugs that stimulate sexual performance by acting selectively on the adrenergic, serotonergic, or cholinergic system. Yohimbine, a selective antagonist of the alpha-2 receptors; 8-OH-DPAT, a selective agonist of the 5-HT 1A receptors; and oxotremorine, a muscarinic agonist, were administered to male rats neonatally treated with clomipramine that showed sexual behavior impairments. Yohimbine and oxotremorine induced only a slight improvement of sexual deficiencies. 8-OH-DPAT not only restored sexual behavior to normal levels, but induced facilitation in most of the copulatory parameters. These results suggest that neonatal treatment with clomipramine induces sexual deficits acting mainly on the adrenergic and cholinergic systems, while the serotoninergic system seems to be preserved.

Lack of Effect of Corticosterone Administration on Male Sexual Behavior of Rats

RETANA-MARQUEZ, S., H. BONILLA-JAIME AND J. VELAZQUEZ-MOCTEZUMA. Lack of effect of corticosterone administration on male sexual behavior of rats. PHYSIOL BEHAV 63(3) 367–370, 1998.—The increase in plasma levels of corticosteroids as part of the stress response has been associated with failure in the reproductive function in most vertebrate species, both in females and males. Recently, we have shown that male sexual performance in rats is readily affected by different stressors, both acutely and chronically applied. However, there are few reports that directly correlate the increase in corticosteroid levels with the behavioral effects of stress. In this study we investigated whether the administration of corticosterone, either acutely or chronically, could reproduce the effects of stress on male sexual behavior in the male rat. Four doses of corticosterone (0.5, 1, 2, and 4 mg) or the vehicle, were administered during four consecutive days to sexually experienced males. Male sexual behavior was assessed after the first and the fourth injection. After the last test, males were killed and levels of corticosterone and testosterone were measured by HPLC. We observed an increase in corticosterone plasma levels in a dose-dependent manner. None of the sexual behavior parameters, however, was modified. Plasma levels of testosterone were not modified by corticosterone administration. Both steroids were increased in response to sexual activity, though. These data show that, unlike amphibians and female mammals, corticosteroids do not alter sexual behavior in male rats and suggest that the effect of stress on male sexual behavior cannot be explained by increases in corticosterone.

Male sexual behavior is associated with LHRH neuron number in middle-aged rats

LHRH administration is reported to facilitate male sexual behavior. The aim of the present study was to investigate whether male sexual behavior is associated with the number of LHRH neurons in the forebrain in middle-aged rats. Male Long–Evans rats (18–19 months) were assigned to three groups on the basis of sexual performance: (1) group MEI consisted of rats showing complete copulatory patterns, including mounts, intromissions and ejaculations, (2) group MI was composed of rats showing mounts and intromissions, but no ejaculation and (3) group NC were non-copulators, i.e. they did not show any copulatory behavior. Young adult rats (4–5 months), displaying sexual behavior, were used as controls. Following the sexual behavior tests, the number of LHRH neurons in the medial septum (MS), organum vasculosum of the lamina terminalis (OVLT), preoptic area (POA) and anterior hypothalamus (AH) was determined by immunocytochemistry. No difference was seen in the total number of LHRH neurons in these combined brain areas between group MIE and young controls. In the three middle-aged groups, the total number of LHRH neurons was greatest in group MIE, less in group MI, and lowest in group NC. In general, a similar trend was seen separately in the MS, OVLT and POA. These results suggest that changes in the number of LHRH neurons in the forebrain, in most cases, are age-related, at least in the middle-aged rats, but they also seem to be associated with male sexual performance.

Anti-sexual and anxiogenic behavioral consequences of corticotropin-releasing factor overexpression are centrally mediated.

Corticotropin-releasing factor (CRF) acts as a neurotransmitter in brain to promote behavioral responses such as flight and immobility, which have adaptive value in the context of exposure to environmental stressors. CRF also suppresses behavioral repertoires such as mating, which are incompatible with such threat-related coping responses. In this study, we employed transgenic (Tg) mice which overexpress CRF in brain and exhibit a constitutive and persistent phenotype of emotionality in order to determine the consequences of long-term CRF excess on indices of reproductive success, male sexual performance and female sexual receptivity. Sexual performance of CRF Tg males was relatively intact, whereas female receptivity was masked in CRF Tg mice by active rejection of sexually experienced male counterparts. This impairment in social interaction was only partially normalized by the serotonin antagonist, methysergide, which enhanced olfactory exploration of the still non-receptive CRF Tg females. Moreover, the anxiogenic-like character of CRF Tg mice is likely to be centrally mediated, since attenuation of hypercorticosteronemia by adrenalectomy did not alter either impaired sexual receptivity or fear-like behavior in an animal model of anxiety. Thus, overexpression of CRF in the brain results in a variety of adverse consequences including diminished social interactions.

Effect of kidney transplantation and cyclosporine treatment on male sexual performance and hormonal profile: A prospective study

Effect of kidney transplantation and cyclosporine treatment on male sexual performance and hormonal profile: A prospective study

Exposure to a recently mated male increases ram sexual performance

Previous studies reported that male sheep sexual performance does not improve following the observation of heterosexual behavior, which is in contrast to male cattle, goats, pigs and horses. The purpose of this study was to investigate the possibility that exposure to a recently mated ram may enhance ram sexual performance. Eight sexually experienced rams (1 year of age) were assigned to either mated ram stimulus (MRS) or non-mated ram stimulus (NMRS) conditions in a switchback design. The rams in the MRS condition were briefly (10 min) exposed to a penmate who had mated an ewe immediately beforehand. The males in the NMRS condition were exposed to a penmate who had been placed in an empty pen. The rams were allowed to freely investigate their respective stimulus penmate and then each male was placed with an estrous ewe for 15 min. The frequencies of anogenital sniffs, leg kicks, flehmen lip curls, mount attempts, mounts and ejaculations were recorded. Ejaculatory latencies were also recorded. Mean courtship (anogenital sniffs and leg kicks) and mounting (mount attempts and mounts) behavior frequencies were higher for the MRS condition ( P = 0.010 for both). Similarly, the individual mean frequencies of anogenital sniffs, leg kicks, mount attempts and mounts were higher when males interacted with a ram which had just mated ( P = 0.046; 0.016; 0.048; 0.029, respectively). Mean flehmen lip curl and ejaculation frequencies were not different between the two conditions ( P = 0.900 and 0.700). These data suggest that an odor cue associated with the ewe or mating, perse, was emitted by the penmate which was allowed to mate. This cue then enhanced the sexual performance of rams in the MRS condition.

Hormonal and behavioral responses of male hamsters to females and female odors: Roles of olfaction, the vomeronasal system, and sexual experience

Removal of the vomeronasal organ eliminated androgen surges in male hamsters in response to female vaginal secretions in both sexually experienced and sexually naive males; lesions of the olfactory mucosa had no effect on such responses. Both lesions led to deficits in behavioral responses to vaginal secretions. In response to interactions with estrous females, in contrast, lesions of either system alone had no influence on androgen surges in males (either sexually experienced or naive). Lesions of both systems, however, eliminated androgen surges in sexually naive males but not sexually experienced males. These dual lesions eliminated male mating behavior, while lesions of either system alone had little influence on mating. There were no significant correlations in any experiment between level of behavioral responses and degree of change in androgen levels. Thus, we conclude that the vomeronasal system mediates androgen surges in response to female odors but is not necessary for such responses to females themselves. In sexually naive males the vomeronasal and olfactory systems together are necessary for androgen responses to females. Behavioral responses were influenced by lesions and by sexual experience. Lesions of both systems increased the latency to investigate vaginal secretions, and sexual experience decreased the latency and increased the duration of investigation. Lesions and experience also influenced male sexual performance.

Thiazide diuretics and male sexual dysfunction

AbstractThe associations that have been noted between the clinical use of the thiazide diuretics and impairment of male sexual performance remain enigmatic. Recent studies are reviewed, in which aspects of the male sexual dysfunction in hypertensive men following treatment with thiazide diuretics were examined. The data are interpreted in light of previously published studies on the subject to suggest that penile erectile defects and decrements in sexual activities are specifically related to thiazide administration. A rodent model of thiazideinduced male sexual dysfunction is introduced that documents dose‐related impairment, by hydrochlorothiazide, of penile erectile reflexes and male copulatory performance. The etiology of thiazide‐induced male sexual dysfunction is hypothesized to result from alterations in sodium excretion that alter afferent renal nerve input to hypothalamic areas regulating male sexual responses.

The effects of intrathecal administration of the dopamine agonist apomorphine on penile reflexes and copulation in the male rat.

Relatively high doses of systemically administered apomorphine inhibit penile reflexes. It is possible that these inhibitory effects are due, at least in part, to actions of apomorphine on the lumbosacral spinal cord. The present experiments examined this possibility by injecting apomorphine (10 and 50 micrograms/5.0 microliters vehicle) into the lumbosacral subarachnoid space through chronic, indwelling cannulae. Such injections impaired ex copula penile reflexes, slowed the rate of copulation, and decreased the number of intromissions preceding ejaculation. These results suggest that lumbosacral cord dopamine receptors may normally regulate male sexual performance.

Cognitions and sexual expression in the aging.

This study investigated the relation of cognitions to sexual expression in aging couples where the male had undergone transurethral prostatectomy. Cognitive factors explored were sexual efficacy expectations, value of sex, sexual attitudes, and sexual knowledge. Sexual expression was defined in terms of the following three dimensions: couple sexual frequency, desired sexual frequency, and quality of sexual functioning. Subjects consisted of 32 married couples whose ages ranged from 50 to 77 years. In this sample of sexually active couples, the cognitive variables most highly correlated with all the dimensions of sexual expression were efficacy expectations for the male's sexual performance and individual sexual drive. High sexual efficacy expectations predicted high couple sexual frequency and good male and female sexual functioning. High individual sexual drive predicted high actual and desired couple sexual interaction. In general, it was the male partner's sexual confidence and drive that was highly related to couple sexual expression.

Male Sexual Behavior

This article considers causes of variability in male sexual performance and identifies management techniques that can be used to improve the reproductive success and efficacy of our captive animal populations.

Inhibitory influence of corticotropin releasing factor on components of sexual behaviour in the male rat

Acute microinfusions of ovine corticotropine releasing factor (CRF) into the third cerebral ventricle (III vent.) of sexually experienced male rats produced a dose-dependent suppression of masculine sexual behaviour. This inhibition of male sexual performance induced by CRF could be reversed by simultaneous infusions of naloxone, the opiate receptor antagonist, which when infused without CRF facilitated copulatory performance. These findings suggest that CRF can exert drastic effects on male reproductive behaviour through mechanisms which involve the activation of opioid pathways within the central nervous system. This CRF-linked neurochemical signal may mediate some of the well-known deleterious effects of stressful and noxious stimuli on reproductive function.

Suppression of mating behaviour in the male rat by intracerebroventricular infusions of N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine

Acute microinfusions of N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) into the third cerebral ventricle (III V) of sexually experienced male rats produced a dose-related suppression of masculine sexual behaviour. This inhibition of male sexual performance could be reversed by simultaneous infusions of small doses of pargyline. Three analogues of MPTP, namely, 4-phenyl-1,2,3,6-tetrahydropyrididine, 4-cyano-4-phenylpiperidine and 4-hydroxy-4-phenylpiperidine had no significant effects on any of the parameters of male sexual behaviour. These findings suggest that MPTP may have potent effects on the mechanisms regulating male sexual behaviour in the rat by acting on sites around the third ventricle (arcuate and periventricular hypothalamic nuclei) where there are high MPTP receptor densities and thus provide further evidence for MPTP in neuroendocrine regulation. These responses depend upon the unique structural properties of the MPTP molecule.

Effects of pre- and postpubertal social experience on sexual and social behavior in male and female brown lemmings (Lemmus sibiricus).

The effects of prepubertal social contact and postpubertal mating experience on sexual behavior were examined in male and female brown lemmings (Lemmus sibiricus). Subjects of both sexes were either isolated at weaning (18 days) or then housed with siblings for another 10 days before being isolated. Before testing for sexual behavior at the age of 75 days, half of each group of males received a series of exposures to estrous females and half of each group of females was housed with a stud male. The results of mating tests indicated that whereas prior sexual experience facilitated subsequent copulatory behavior in both sexes, prepubertal interactions subsequently facilitated contact social and sexual behavior in males but did not increase the behavioral scores of females, which engaged in high levels of sexual behavior regardless of prepubertal experience. The effect of prior copulatory activity on male sexual performance could not be attributed to increasing age (i.e., maturational processes) because the behavior of males tested once but at different ages did not differ appreciably. Prepubertal social interaction appeared to predispose males to benefit from sexual experience later in life.

Food conditioning, castration, testosterone administration and sexual behavior in the male rat

Chronically food-deprived male rats, when paired with a female rat in heat, were rewarded by receiving a food pellet following each intromission. Following castration there was a rapid decline in all aspects of male sexual behavior: after 3 weeks all sex behavior had stopped. There were no differences between the conditioned males and their yoked controls. Substitution with two doses of testosterone (through silastic implants) restored sexual behavior, but equally so in the conditioned and the control animals. Removal of the testosterone implant again caused a very rapid decline in sexual behavior, no differences between experimental and yoked control males. These results suggest that food, as a non-sexual stimulus, does not cause hungry male rats to continue to copulate for prolonged periods following castration. Furthermore, the combination of chronic food deprivation plus castration do summate with each other in the very rapid decline and cessation of male sexual performance.

Effect of maintenance hemodialysis on male sexual performance.

Prior studies have suggested that male patients with uremia suffer from sexual dysfunction that worsens when they are placed on maintenance hemodialysis. The authors report a prospective study of the effect of maintenance hemodialysis on male sexual functioning using nocturnal penile tumescence (NPT) measures and detailed sexual histories. Twenty men already on maintenance hemodialysis and 23 men with advanced renal failure who began maintenance hemodialysis within 4 months of entering the study were followed at 4-month intervals for 1-year and 6-month intervals for the following 18 months. Sexual performance as assessed by NPT, frequency of intercourse, and complaints of erectile failure remained remarkably stable over time for both groups. When renal failure patients moved to maintenance hemodialysis, their frequency of intercourse increased significantly despite stability of NPT. These results suggest not only that maintenance hemodialysis does not worsen sexual functioning, but that adaptation to a sexual deficit is possible after starting hemodialysis.

Sexual behavior in male rhesus monkeys elicited by electrical stimulation of preoptic and hypothalamic areas

Electrical stimulation of the preoptic area, lateral hypothalamus or dorsomedial nucleus of the hypothalamus (DMH) has produced sexual behavioral responses in 11 male rhesus monkeys. At a short latency following the onset of each train of stimulation, the stimulated males would mount estrogen-treated, receptive females. Quantitative measures of the elicited sexual behavior, in 4 males, were applied to describe differences between the effects of preoptic and DMH stimulation on male sexual performance. As compared to spontaneous sexual activity, stimulation of the DMH produced mounts of longer duration, with more thrusts per mount, higher thrusting rates and a greater number of ejaculations per test session; refractory periods between successive ejaculatory episodes were shortened as a result of stimulation-induced mounting behavior. Preoptic stimulation also induced mounts of longer than normal duration characterized by a slightly increased number of thrusts per mount. In contrast to DMH stimulus effects, however, thrusting rate was decreased significantly by preoptic stimulation and ejaculation did not occur even after multiple stimulus-induced mounts. Penile erections were elicited by stimulation of the anterior hypothalamus, ventromedial nucleus and the posterior hypothalamus in socially isolated or restrained males; however, stimulation of these same sites was ineffective for provoking sexual behavioral responses when tests were performed while the males were paired with receptive females.

Studies on reproductive behaviour in primates

Sexual interaction between oppositely sexed pairs of rhesus monkeys depends upon a multiplicity of factors, but important among these is (1) the state of female receptivity and related to this, but independent of it, (2) female attractiveness as a sexual stimulus to the male. Female receptivity. Ovarian hormones appear to influence female proceptive behaviour (behaviour shown by the female which is likely to initiate copulatory or mounting activity in the male) and not unreceptiveness, as evidenced by changes in the female monkey’s active participation in sexual interactions during the follicular and especially mid-cycle periods. Ovariectomy reduces this proceptive behaviour but fails in the short term to induce unreceptiveness, which only becomes apparent following adrenalectomy. Adrenal androgens are important for full receptive behaviour in the female primate since adrenalectomised females become less unreceptive and more proceptive following administration of either subcutaneous testosterone or by implants of testosterone localized in the anterior hypothalamus. Thus, while the ovarian hormones are primarily involved in the female’s proceptive behaviour, adrenal’androgens are important for receptive behaviour and, in their absence, elements of unreceptive behaviour occur. Female attractiveness. The female primate will permit the male to mount throughout her menstrual cycle, and changes in the sexual interaction which occur during the menstrual cycle are strongly influenced by changes in the stimulus value of the female. Olfactory cues have been shown to be of importance in communicating the sexual attractiveness of the female rhesus monkey, oestrogen enhancing attractiveness and progesterone diminishing attractiveness. However, the behavioural response of males to odour cues concerning female attractiveness varies among individuals and, in a social context, past experiences and partner preferences readily modify the kind of behavioural response obtained. In this respect, the olfactory system appears to have a dual role in sexual interactions being concerned with both male sexual arousal and performance, and this, in turn, may be subserved by separate neural pathways between the olfactory bulbs and anterior hypothalamus. NESTING BEHAVIOUR OF THE DOMESTIC HEN D.G.M. WOOD-GUSH and M.J. GENTLE ARC Poultry Research Centre, West Mains Road, Edinburgh (Great Britain)

Chapter 26. The Cannabinoids: Therapeutic Potentials

A review of the therapeutic potentials of the cannabinoids is presented. With respect to the antifertility aspects of cannabinoids, 2 mg delta 9-THC suppressed luteinizing hormone secretion in rats and 2 and 3 mg/kg resulted in a deterioation of male sexual performance. A new chapter in marijuana research was opened in 1964 with the identification of delta 9-tetrahydrocannabinol as the active ingredient. Antiedema, analgesic, antipyretic, antiinflammatory, antifertility, antiepileptic, anticonvulsant, antihypertensive, cardiotonic, pulmonary, and antidepressant effects along with potentiation of barbiturates and analgesics are reviewed leading one to the conclusion that marijuana is "a drug for all reasons". During the past decade many investigators have pursued the possibility of modification of the delta 9 structure to delineate activities. 1 compound, Abbott 40656, SP106, a water-soluble benzopyran derivative is presently under Phase 1 clinical evaluation as a sedative-hypnotic.

Ejaculation by male rhesus as a function of the female partner

Nine adult male rhesus monkeys were given eight 10-min tests of sexual behavior with eight ovariectomized female rhesus pretreated with estradiol benzoate. Males differed significantly in the number of tests during which they ejaculated, and females differed in the frequency with which specific males ejaculated when tested with them. With phylogenetic increase in neocortex, pair compatibility may be as important as hormonal stimulation in regulating male sexual performance. If this is correct, the problem of understanding the determinants of primate sexual behavior becomes more formidable.