Component Analysis of Male Sexual Behavior

Coenzyme Q10 enhances testicular functions and sexual behavior through regulating steroidogenic-related gene expression and inflammatory pathways of Japanese quail (Coturnix japonica) aganist cadmium

A progressively essential bird of high economic significance for meat production and commercial egg is the Japanese quail, and so more experiments are necessary to improve the productivity of these birds under stressful encounters. The current work was performed to define the influences of Coenzyme Q10 (CoQ10) on growth, sexual behavior, and testicular characteristics (size of the gonad, traits of spermatic features, levels of plasma testosterone, steroidogenic-related gene expression) of Japanese quail (Coturnix coturnix japonica) aganist cadmium (Cd) administration. Chicks of quail (n = 250), 14 days old of age were distributed into 4 groups: basal ration (Group 1), basal ration and CoQ10 at 100 mg/kg ration (Group 2), basal ration and Cd at 50 mg/kg ration (Group 3), and CoQ10 + Cd (Group 4). Several parameters relating to productive performance, such as weight of the body, weight gain, feed intake, and the conversion ratio of feed, were evaluated. Constant visual scanning of the quails was performed to observe their sexual behaviors. Sperm characteristics, plasma testosterone levels, and testicular inflammatory markers of interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) were also determined. Oxidative-antioxidant redox status in the testes was evaluated by analyzing MDA level, GPx, and SOD activities. Steroidogenic-related gene expression in the testes (CYP17A1, StAR, 3β-HSD, and Cyp19) was also examined. In addition, testicular apoptosis was assessed by monitoring the alterations in the local expression of stress-induced (HSP70), proteins of anti-apoptotic marker (Bcl-2), and pro-apoptotic markers (caspase-3 and Bax). Cd administration hurts body performance, sexual behavior, and testicular efficiency parameters. Interestingly, CoQ10 supplementation improved reproductive performance. Moreover, it significantly increases the % of birds exhibiting sexual behavior and enhances testicular functions, which were damaged by Cd administration, by enhancing plasma testosterone level, antioxidative enzyme activity, and sperm quality traits while reducing the MDA and pro-inflammatory markers. Furthermore, downregulation of pro-apoptotic factor expression, though it increased the expression of the anti-apoptotic protein, was recorded. Correspondingly, CoQ10 revealed a marked upregulation in the expression of steroidogenic-related genes. Conclusion: It is established that the consumption of CoQ10 in the ration of Japanese quail, following a Cd adminstration, improves productive performance, sexual behavior, and several testicular function parameters as a potent antioxidant.

Testosterone is essential for alpha(2)-adrenoceptor-induced antinociception in the trigeminal region of the male rat

Activation of the alpha(2)-adrenoceptor has been shown to produce antinociception. We have previously shown that the antinociceptive effect of clonidine, an alpha(2)-adrenoceptor agonist, is sex-specific and is abolished by exogenous estrogen in ovariectomized rats or high level of endogenous estrogen in proestrous females. Here, we investigated whether testosterone mediates the antinociceptive effect of clonidine in the trigeminal region of the male rat. Clonidine (7 microg/5 microl) was injected intracisternally through a PE-10 cannula implanted dorsal to the trigeminal region in orchidectomized (GDX) male Sprague-Dawley rats. In separate groups, testosterone propionate (250 microg/100 microl; GDX+T) or beta-estradiol benzoate (100 microg/100 microl; GDX+E) were injected subcutaneously 24 and 48 h respectively prior to the N-methyl-D-aspartic acid (NMDA)--or heat-evoked nociceptive test. NMDA-induced number of scratches or duration of scratching behavior did not change significantly in control groups with or without hormonal replacement. Clonidine significantly reduced both measures only in the GDX+T group but not in GDX or GDX+E group. Clonidine also significantly increased head withdrawal latency (HWL) in the GDX+T group, but not in GDX or GDX+E group. The antinociceptive effect of clonidine was reversed by yohimbine, an alpha(2)-adrenoceptor antagonist, in GDX+T group. We conclude that testosterone is required for the expression of antinociception produced by selective activation of the alpha(2)-adrenoceptor in the trigeminal region of the male rat. These findings further our understanding of sex-related differences in the modulation of nociception and may provide insight into development and administration of analgesic agents in young vs. aging men.

Sex-specific modulation of spinal nociception by alpha2-adrenoceptors: differential regulation by estrogen and testosterone

Sex-related differences in antinociception produced by the activation of alpha(2)-adrenoceptors (alpha(2)-ARs) have been reported, however, the precise role of gonadal steroids is still unknown. Hence, we hypothesized that estrogen and testosterone modulate antinociceptive effects of clonidine (an alpha(2)-AR agonist) on N-methyl-D-aspartate- (NMDA) and heat-induced spinal nociception. We also investigated whether estrogen or testosterone alters the expression of alpha(2A)-adrenoceptors in the spinal cord. Sprague-Dawley (SD) rats were implanted with PE10 cannulae in the intrathecal space of the lumbosacral spinal cord and divided into male, proestrous and diestrous female, ovariectomized (OVX), estradiol-treated OVX (OVX+E), castrated male (GDX), testosterone (GDX+T) and estradiol-treated castrated male (GDX+E) groups. Clonidine dose-dependently inhibited NMDA-induced scratching behavior in the male and OVX groups but to a significantly lesser extent in the OVX+E group. It also increased the tail withdrawal latency in the male, OVX, diestrous and GDX+T groups but not in the OVX+E, proestrous, GDX and GDX+E groups. Levels of alpha(2A)-AR mRNA were significantly higher in the OVX, estradiol-treated OVX, GDX and GDX+E animals. In contrast, alpha(2A)-AR protein levels were higher in estradiol-treated OVX, GDX, GDX+T and GDX+E animals as compared with the male. Indeed, no correlations were observed between changes in the mRNA or protein levels of alpha(2A)-AR and behavioral observations. These results support our hypothesis that sex-related differences in alpha(2)-AR-mediated modulation of spinal nociception are gonadal hormone-dependent: estrogen attenuates antinociceptive effects in females whereas testosterone is required for the expression of antinociception in males. In addition, results also revealed that the mechanism of action of gonadal hormones may not involve a global alternation in expression of alpha(2A)-AR in the spinal cord. Estrogen-induced attenuation of alpha(2)-AR-mediated inhibition of nociception could contribute to the higher prevalence of pain syndromes in women.

Only self-paced mating is rewarding in rats of both sexes

When rats are mated in a traditional mating chamber (with one male and one female) in which the male dictates the pace of the copulatory sequence, males develop a reward state as evaluated by conditioned place preference (CPP). In this mating situation no reward state is induced in females. However, when female rats are able to control (pace) the rate of sexual stimulation, thereby reducing the aversive consequences associated with mating, a clear CPP is observed. In the present study the CPP paradigm was used to determine whether if the reinforced state induced by coital interactions in male rats can be maintained when females pace the sexual interaction. Adult male and female rats were mated in one of two different conditions: (1) where subjects were able to pace their coital interactions or (2) where subjects were not able to pace their sexual contacts. The results showed that when males had control over the sexual interaction they developed a clear place preference while males that mated with females that paced their coital contacts did not develop CPP. Similarly, only females that were able to pace their sexual contacts developed place preference. These results suggest that coital interactions in males, as well as in females, can induce a reward state only when they are able to control the sexual interaction. Under seminatural conditions sexual behavior in rats is highly promiscuous, they mate in groups and repeatedly change partners in the middle of copulation. This behavioral sequence allows both, male and female to control the rate of sexual interaction, assuring the induction of a reward state outlasting the actual performance of coital responses.

Sexual motivation--an inquiry into events determining the occurrence of sexual behavior

For the individual engaged in it, sexual behavior has no finality or purpose other than its own execution. Data are presented showing that the execution of sexual reflexes can promote learning, i.e. it functions as reinforcement. Furthermore, positive affect is generated. Based on these principles, a model of sexual motivation has been elaborated. The conceptual framework is the incentive motivation theory previously proposed by Bindra D, A motivational view of learning, performance, and behavior modification, Psychol Rev 1974: 81:199-213; A Theory of Intelligent Behavior, New York: Wiley, 1976; How adaptive behavior is produced: a perceptual-motivational alternative to response reinforcement, Behav Brain Sci 1978; 1:41-52. Although the model is intended for application to most mammals, the rat is used as example. Essentially, sexual approach behaviors are activated by appropriate incentives (conditioned in the male, unconditioned in the female). Approach is, in the inexperienced male, followed by the execution of copulatory reflexes as a consequence of accidentally obtained tactile stimulation of the perineal region. In the female, copulatory acts are activated by tactile stimulation of the flanks and hinds provided by the mounting male. The role of conditioning for the execution of copulatory reflexes and for the acquisition of incentive value of neutral stimuli is analyzed. It is also shown that the incentive properties of sexual acts are not substantially different from those of other incentives. Sexual exhaustion is suggested to be either a case of negative alliesthesia or of stimulus habituation and the Coolidge effect is, in consequence, an example of dishabituation. Studies in women and men support this proposal. It is emphasized that sexual behavior is best understood as being entirely mechanistic albeit not deterministic.

Neuropeptide Y (NPY) levels in alcoholic and food restricted male rats: implications for site selective function

Neuropeptide Y (NPY) has been implicated in the control of ingestive, cardiovascular, and reproductive function. Blood pressure and sexual function were examined in Long-Evans rats receiving 6% ethanol-containing or calorically matched liquid diets, or rat chow ad lib. After 12 weeks of exposure, rats were sacrificed and plasma hormone levels and NPY content of microdissected brain regions were determined. Neither long-term alcohol ingestion nor caloric restriction were associated with major decrements in copulatory behavior. Long-term alcohol ingestion was associated with decrements in erectile function ex copula. Long-term alcohol ingestion was also associated with: (i) a moderate degree of hypertension; (ii) a failure to gain weight; (iii) decrements in circulating levels of LH, testosterone, and ACTH (but not progesterone); and (iv) increased corticosterone levels. Long-term alcohol ingesting and calorically-restricted rats exhibited alterations in daily feeding patterns. These physiological changes in response to long-term alcohol ingestion or caloric restriction were associated with neural site-selective differences in NPY content. Elevated NPY in the paraventricular nucleus was associated with voluntary (as in alcohol ingestion) or involuntary (as in caloric restriction) reductions in food intake. Differences in NPY in the suprachiasmatic and ventromedial nuclei were associated with the differences in feeding patterns. The decrements in hormone levels were associated with higher levels of NPY in the median eminence and in the arcuate nucleus.

The inhibitory effects of propranolol on genital reflexes in male rats

We have previously reported that propranolol adversely affects sexual behavior in male rats. To elucidate whether the effects of propranolol might involve decrements in ability, we examined two components of sexual function ex copula--ejaculatory reflex capacity and erectile reflexes. In the first study, we examined the effects of various doses of (+/-)-propranolol (1.25-10 mg/kg) administered subcutaneously. Marked inhibition was observed, evidenced by increases in the latency to ex copula ejaculation and to initial erection and decrements in the number of seminal emissions and in the number of erectile reflexes. Analyses of dose-response relationships indicated that the degree of inhibition increased with increasing dose. In the second study, we evaluated the stereo-selectivity of the responses. Both (+)- and (-)-propranolol (1.25 mg/kg) significantly inhibited ejaculatory reflex potential, and although (+)- and (-)-propranolol significantly inhibited erectile reflexes, (-)-propranolol had a greater effect. The data are interpreted to indicate that a) propranolol-induced sexual dysfunction involves both motivational and ability aspects; and b) propranolol-induced inhibition of genital reflexes may be due, at least in part, to mechanisms other than beta-adrenoceptor blockade.

The inhibition of sexual behavior in male rats by propranolol is stereoselective

We have previously reported that administration of racemic mixtures of propranolol was associated with a marked inhibition of mating behavior in male rats. To compare the effects of (+)-propranolol, (-)-propranolol, and (+/-)-propranolol in sexually experienced males, rats ejaculating in four or more mating tests were divided into three groups (N = 16 per group) such that no differences in parameters of copulatory behavior were evidence in preexperimental tests. No major effect of propranolol on parameters of behavior associated with initiation of sexual behavior was evident. In contrast, other measures of behavior were profoundly modified. The ejaculatory threshold, indicated by the number of intromissions preceding ejaculation, was increased after (+)- and (+/-)-propranolol, but not (-)-propranolol. The number of mounts without intromission preceding ejaculation was increased only after (+/-)-propranolol. A decrease in copulatory efficacy was evident after (-)- or (+/-)-propranolol, but not after (+)-propranolol. Increases in ejaculation latency, intercopulatory interval, and postejaculatory interval were observed after (-)- and (+/-)-propranolol, but not after (+)-propranolol. In summary, the present data indicate that the (-) isomer of propranolol is the active form necessary for the inhibitory effects of propranolol on male sexual function. We suggest that this inhibition is due to specific receptor-mediated mechanisms, involving beta-adrenoceptors and 5-HT1A receptor interactions.

Prepubertal testosterone treatment of neonatally gonadectomized male rats: defeminization and masculinization of behavioral and endocrine function in adulthood

Testosterone (T) administered well after the neonatal "critical" period to females at a dose approximating male levels permanently defeminizes reproductive function (see companion publication). To obtain comparable data for the male, neonatally gonadectomized (NeoGx) males received T filled or empty Silastic capsules during days 15-30 of age and were studied in adulthood. Compared to controls, the T treatment resulted in reduced lordosis and proceptive behaviors, increased mounting and intromission behaviors without differences in penile reflexes or size, and reduced plasma FSH and LH surges. Twenty of twenty-three sham-NeoGx males, but only one NeoGx male, showed ejaculatory behavior despite equivalence in penile reflexes and size after detaching a frenulum when present on the penis. These results show that T can still act on neural substrates well beyond the neonatal period to defeminize and masculinize endocrine and behavioral function in the male rat. A comparison with effects in females indicates a sex difference, the male appearing to be more sensitive to these actions of T.

Aging-induced decrements in neuropeptide Y: the retention of ejaculatory behavior is associated with site-selective differences

Neuropeptide Y (NPY) has been implicated in the control of reproductive and cardiovascular function. We observed an age-related decrease in the number of males copulating to ejaculation and a moderate systolic hypertension in middle-aged (16- to 17-month-old) rats. NPY content was examined in microdissected brain nuclei in 5 groups of rats: 2 groups of young rats, 1 heterosexually naive and the other ejaculating in 3 successive mating test; 3 groups of middle-aged rats, 1 heterosexually naive, 1 group that had extensive sexual experience but failed to ejaculate in tests at 16.5 months of age, and the third continuing to ejaculate at 16.5 months of age. NPY levels were found to vary depending on the brain area, the age of the animals, and the maintenance of ejaculatory behavior. In sexually naive middle-aged males, NPY levels were uniformly lower than in younger males. There were no differences in NPY levels of young animals, regardless of sexual experience. In the medial preoptic area, the group that retained ejaculatory behavior through 16.5 months of age, had higher levels of NPY than those observed in young sexually experienced rats. In sexually experienced rats that were no longer ejaculating at 16.5 months of age levels were lower than all other groups except the sexually naive middle-aged group. In the hypothalamic arcuate nucleus, levels were equivalent in the young groups and in the middle-aged rats that retained ejaculatory behavior, being greater than in the middle-aged rats that were no longer ejaculating or were sexually naive.(ABSTRACT TRUNCATED AT 250 WORDS)

Stimulatory effects of quinelorane on yawning and penile erection in the rat

Quinelorane, a highly selective D2 dopamine agonist, was assessed for its ability to induce the penile erection/stretch-yawn syndrome. Quinelorane (0.1-100 micrograms/kg s.c.) or saline vehicle was administered to adult male Sprague-Dawley rats just prior to a 30 min. observation period. Significant dose-related increases in erections were observed in the drug treated animals at 3-100 micrograms/kg. Yawning was also increased at 3-100 micrograms/kg, with highest levels occurring at 10 micrograms/kg. Defecation was stimulated between 10 and 100 micrograms/kg. The stimulatory effects of 30 micrograms/kg of quinelorane on erection, yawning and defecation were blocked by haloperidol (0.1-0.3 mg/kg) but not by domperidone (0.1-1.0 mg/kg). No significant effects of quinelorane on seminal emission were observed. These findings indicate that in addition to its stimulatory effects on sexual activity, quinelorane also acts on D2 receptors in the central nervous system to stimulate erection in the penile erection/stretch-yawn model.