Sexual behavior in response to testosterone in old long-term-castrated rhesus males

The sexual behavior of 20-year-old long-term-castrated and intact male rhesus macaques (Macaca mulatta) was observed. In the first experiment we compared the sexual behavior of males tested in 1980 with their performance in 1970 (before castration and sham castration) and in 1971 (1 year after the operation). In 1971 and 1980, the castrated males were tested while under testosterone propionate treatment. The castrated and intact males did not differ in any measures of sexual behavior over the 10-year period, but both groups showed a decline in the percentage of tests with intromissions and ejaculations; a decline in the rates of contacting, mounting, and intromitting; and an increase in the latencies to contact, intromit, and ejaculate. In a second experiment, the sexual performances of old castrated and intact males were compared to those of young intact males (8 to 12 years). The intromission rate and the percentage of tests with intromissions were significantly greater in young males than in old intact males, but did not differ from values for old castrated males. The old castrated and old intact males did not differ from each other in these measures. Young males had a higher percentage of tests with ejaculation than either group of old males. We have concluded that old long-term-castrated rhesus males retain the potential to display sexual behavior at levels comparable to those observed in old intact males.     

Sexual performance of old and young male rhesus macaques following treatment with GnRH

GnRH has been reported to facilitate sexual performance in a number of species. To determine whether the same was true for rhesus monkeys we measured sexual behavior and serum levels of testosterone (T) and luteinizing hormone (LH) following control tests and after treatment with two doses of GnRH. In the first experiment, old intact (N = 11) and old T-implanted, castrated (N = 4) rhesus macaques were examined. Mean intromission rate of old intact males was significantly lower following treatment with 100 micrograms of GnRH than following control injections. Other measures of sexual behavior did not differ across treatments. There were no significant treatment effects among the old castrated males. The failure to facilitate sexual performance may have been due to the age of the males and not to the species under study. Thus, in a second experiment the effects of GnRH were examined in young rhesus males. Again, there was no facilitation of sexual performance. This cannot be accounted for by a failure of GnRH to produce a physiological response. For both old and young intact males serum levels of LH and T increased significantly after treatment with both doses of GnRH. LH but not T levels increased significantly in the T-implanted males.     

The effect of human chorionic gonadotropin on serum levels of testosterone, estradiol, and sexual behavior in young and old rhesus males

Sexual behavior and serum levels of testosterone (T) and estradiol (E) were examined in five young and six old rhesus males (Macaca mulatta) before and after the injection of 500 and 1000 IU of HCG. The serum levels of T and E increased in both young and old males after injection of either dose of HCG. Serum levels of T were significantly higher in young than in old males in the period following the last injection of 1000 IU of HCG. Old males had significantly higher levels of serum E during treatment with 1000 IU of HCG, but serum E levels in the two groups did not differ before or after treatment. Serum levels of T and E did not differ between the young and old males when injected with 500 IU of HCG. HCG had no effect on sexual performance and the differences in levels of sexual performance between the young and old males were not eliminated.     

Adult sexual behavior deficits and altered hormone levels in male hamsters given steroids during development

Masculine sexual behavior and adult gonadotrophin and steroid hormone levels were assested in intact male hamsters (approximately 100 days old) which had received exogenous steroids on days 2–10 of postnatal life. Estradiol benzoate (EB), testosterone propionate (TP) or testosterone caused deficits in sexual behavior including elimination or decreases in ejaculatory capacity and intromission frequency. Androstenedione or progesterone had no effect on male sexual behavior. EB treatment caused increases in serum LH and FSH levels, normal serum androgen levels and reduced testis weight. TP neonatally administered resulted in decreased serum androgens and decreased testis weight but normal gonadotropin levels. Progesterone did not affect hormone levels or testis weight. Adult castration and TP replacement therapy in males treated neonatally with TP did not reinstate normal levels of ejaculation.     

Testosterone is more effective than dihydrotestosterone plus estradiol in activating sexual behavior in old male rats

Sexual behavior declines in old male rats, and testosterone therapy does not restore the behavior to levels found in young males. If as a result of aging, old males have less capacity to aromatize or reduce testosterone, dihydrotestosterone plus estradiol treatment should be more effective than testosterone treatment in restoring sexual behavior in old castrated males. In a test of this hypothesis, the sexual behavior of old (24 months) castrated Fischer 344 males given injections of testosterone propionate (TP) or dihydrotestosterone propionate (DHTP) plus estradiol benzoate (EB) and that of old sham-operated males given injections of vehicle were observed. The DHTP/EB proved to be less effective overall than the TP in increasing sexual behavior in old castrated males. In a second experiment, young (3 months) and old (30 months) males were tested to verify that the reduced effectiveness of DHTP/EB treatment was age-related. Testosterone propionate and DHTP/EB were equally effective in restoring most measures of sexual behavior in young castrated males. In old castrated males, DHTP/EB treatment was no more or less effective than TP treatment in increasing these same measures. Neither hormone increased the behavior of old males to the level found in young males. Since DHTP/EB treatment is less effective than TP treatment in stimulating sexual behavior in old males, a reduced capacity to aromatize or reduce testosterone is not a likely explanation for decreased responsiveness to testosterone in old male rats.     

Age-related deficits in brain androgen binding and metabolism, testosterone, and sexual behavior of male rats

Brain androgen binding and metabolism, serum testosterone (T), and sexual behavior were measured in old and young male Fischer 344 rats. After completion of sexual behavior tests, blood was collected for T assay and brains were removed for simultaneous measurements of cytosolic (ARc) and nuclear (ARn) androgen receptors and aromatase activity (AA) in the preoptic area (POA), hypothalamus (HYP) and amygdala (AMG). In Experiment 1, old and young intact males were examined. None of the old males ejaculated in any of the tests of sexual behavior whereas all of the young males ejaculated. The old males had lower levels of serum T, lower levels of ARn in the POA and HYP and lower levels of AA in the POA. The ARc levels of the old and young males did not differ. Experiment 2 was designed to determine if the deficits in brain androgen binding and metabolism were due to low levels of T. Old and young T-treated gonadectomized (GX-T) males and young intact (I) males were examined. T levels were comparable in the young and old GX-T males and were higher in each of these groups than in the young I males. In sexual behavior tests, all of the young but only 25% of the old GX-T males ejaculated. Although ARn levels in the old GX-T males were lower than in the young GX-T males, they were comparable to the young I male levels. No age-related differences in T induction of AA were observed.(ABSTRACT TRUNCATED AT 250 WORDS)     

Correlation of diurnal changes in hormones with sexual behavior and age in male rhesus macaques

—We designed this study to determine whether the sexual behavior of male monkeys changes on a diurnal schedule that coincides with changes in the levels of hormones such as luteinizing hormone (LH), testosterone, estradiol, and cortisol, and whether these differences vary with age. Old (n=8) and young (n=8) males were bled and given sexual behavior tests eight times at 0900 and eight times at 2100. The old and young males did not differ in mean serum levels of testosterone, estradiol, cortisol, or LH. Testosterone and LH levels were lower at 0900 than at 2100 (p<0.01), and estradiol and cortisol levels were higher at 0900 than at 2100 (p<0.01). The young males had higher percentages of tests with erections, mounts, intromissions, and ejaculations than the old males (p<0.01). The rates contacting, mounting, and intromitting were higher at 0900 than at 2100 (p<0.05). We failed to confirm previously obtained correlations between hormone levels and sexual performance. This failure led us to conclude that any significant correlation between sexual behavior and hormone levels must be regarded as tentative unless repeated in successive independent studies.     

Relationships between the serum levels of soluble leptin receptor and free and bound leptin in non-pregnant women of reproductive age and women undergoing controlled ovarian hyperstimulation

BACKGROUND: The aim of this study was to investigate the relationships between the serum levels of soluble leptin receptor (SLEPR), and total, free and bound leptin, and the change in the serum SLEPR level during an IVF cycle. METHODS: Serum concentrations of leptin and SLEPR were measured in 50 Japanese women of reproductive age, and 20 patients participating in an IVF programme. The total leptin was fractionated into free and bound portions by gel filtration chromatography. RESULTS: The SLEPR level was negatively correlated with the body mass index (BMI) (r = -0.548, P < 0.0001), total leptin (r = -0.433, P < 0.0001), the percentage of free leptin (r = -0.732, P < 0.0001) and the absolute free leptin concentration (r = -0.506, P < 0.0001). The SLEPR level was positively correlated with the percentage of bound leptin (r = 0.730, P < 0.0001), whereas there was little variation in the absolute bound leptin concentration, regardless of the BMI or SLEPR concentration. During the IVF cycle, total and free leptin elevated during maximal ovarian stimulation, whereas there was no significant difference in the SLEPR concentration. CONCLUSIONS: The results demonstrate a skillful mechanism where a change in the serum SLEPR level regulates, in part, the biological activity of leptin in the circulation.     

Sexual behavior and serum levels of prolactin, testosterone, and estradiol in young and old rhesus males.

It has been suggested that increased prolactin levels may contribute to decreased libido in aging male primates. To test this hypothesis, the association of sexual performance and serum prolactin levels was determined in young (10 year) and old (25.7 year) male rhesus macaques. Old males displayed significantly lower levels of sexual behavior than young males but their serum prolactin levels were not significantly higher. The correlation between prolactin levels and different measures of sexual behavior also were not significant for either old or young males. These data suggest that elevations in prolactin levels do not significantly contribute to the age-related decline in sexual performance in rhesus males.     

A higher burden of small low-density lipoprotein particles is associated with profound changes in the free androgen index in male adolescents

From a young age, males are at higher cardiovascular risk than females. Dyslipidemia, including a higher burden related to small low-density lipoproteins (LDL), plays an important role in precipitating atherosclerosis in both males and females. We investigated sex differences in atherogenic lipoprotein burden and the independent predictors of LDL particle size in children and adolescents. We measured the concentrations of total testosterone, sex hormone-binding globulin, estradiol, total cholesterol, triglyceride, LDL cholesterol, HDL cholesterol, and LDL particle size in 135 children and adolescents (67 boys, 68 girls). The free androgen index was significantly and negatively correlated with LDL particle size (r = -0.273, P = 0.026) in boys, but estrogen and LDL particle size were not related. In a stepwise multiple regression analysis adjusted for body mass index, age, and homeostasis model assessment for insulin resistance, free androgen index was still an independent predictor of LDL particle size in boys (R(2) = 0.075, P = 0.026). The prominent decrease in LDL particle size along with increased testosterone concentrations in males might explain why they are more likely to display atherogenic dyslipidemia from adolescence.     

显微镜下精索静脉结扎术对患者血清睾酮及性功能的影响

目的 评价显微镜下精索静脉结扎术对患者血清睾酮及性功能的影响。方法 选择2013年8月~2017年3月于核工业四一六医院泌尿外科接受显微镜下精索静脉结扎术且有规律性生活的患者为研究对象,在征得患者同意后,分别于术前和术后6个月完成国际勃起功能指数（IIEF-5）量表和中国早泄患者性功能评价表（CIPE-5）的评分,同时检测患者血清性激素水平。结果 72例患者符合研究标准并得到有效随访,患者手术前后总IIEF-5评分、CIPE评分、血清睾酮水平均显著改善,各组手术前后比较差异具有统计学意义（P<0.05）,且患者术后血清游离睾酮的改变与IIEF的改善呈显著正相关。结论 显微镜下精索静脉结扎术不仅可以改善患者血清睾酮水平,对患者勃起功能的改善同样显著。     

Estradiol in the male rat amygdala facilitates mounting but not ejaculation

Mating activates estrogen sensitive neurons in several regions of male rat brain, including the medial amygdala (MEA). Infusion of the aromatase inhibitor, Fadrozole, into the MEA reduced mating, presumably by inhibiting conversion of testosterone (T) to estradiol (E(2)). We investigated whether administering E(2) locally into the amygdala (AMG) would maintain sexual behavior in male rats given systemic Fadrozole to eliminate E(2) elsewhere in the brain. Gonadally intact male rats were divided into two matched groups, based on ejaculatory performance in weekly tests with receptive females. All males received 0.29 mg/kg/day sc Fadrozole and bilateral implants to AMG. E(2)-in-AMG males (N=6 experimentals) received implants tipped with a cured mixture of E(2) in Silastic Medical Adhesive, whereas Vehicle-in-AMG males (N=6 controls) received implants tipped with cured adhesive alone (without E(2)). In E(2)-in-AMG males, postoperative mount and intromission frequency did not differ significantly from pretreatment baseline levels, but ejaculation frequency declined significantly (P<.01). Conversely, in Vehicle-in-AMG males, postoperative mounts and intromissions (P<.01) and ejaculations (P<.01) declined significantly. Postoperative mount and intromission frequency of Vehicle-in-AMG males was significantly lower than that of E(2)-in-AMG males (P<.01), but ejaculation frequency did not differ significantly between groups. This suggests that E(2)-sensitive AMG neurons are important for sexual arousal but not ejaculatory performance.     

Male copulatory behavior induced in female rats by peripheral electric shock

Peripheral skin shock, like administration of testosterone propionate (TP), increased the display of male copulatory patterns in a limited number of ovariectomized female rats. Shock treatment alone led to moderate rates of mounting with thrusting and display of intromission patterns by 2 of the 3 responding females in this group. TP treatment alone resulted in fewer male responses than did shock treatment and failed to produce the intromission pattern. In a group in which both TP and shock were given, all females showed high rates of male mounting and all displayed the intromission pattern. Augmentation of nonspecific arousal by peripheral shock appears to facilitate the display of male sexual behavior in females as it does in males.     

Change of female partner and postejaculatory performance of young and old rhesus males

This study was undertaken to determine whether a change of female partner following ejaculation would reduce the postejaculatory interval (PEI). The male subjects were seven old (mean age 22.4 years) and five young (mean age 12.2 years) rhesus males (Macaca mulatta). The female subjects were four ovariectomized females rendered sexually receptive by treatment with estradiol benzoate. Introduction of a different female following ejaculation significantly reduced the PEI and latency to a second ejaculation in both young and old males. However, a different female did not reduce latencies to preejaculatory levels. The potential for enhanced sexual performance was retained in old rhesus males.     

Serum testosterone measurements

Serum testosterone and especially free testosterone is one of the parameters commonly used to evaluate androgen excess or deficiency. The authors equilibrated serum samples with 14C-labeled testosterone followed by an ammonium sulfate precipitation to compare the "apparent free testosterone concentration" with "total" serum testosterone concentration in the following populations: normal males and females; females presenting with gynecologic problems, particularly hirsutism and/or virilization; and males and females on maintenance hemodialysis. Total serum testosterone for each specimen was assayed with five different commercially available RIA kits encompassing a variety of technics: direct assay technics, assays utilizing extraction procedures prior to RIA; tritium-labeled tracer as well as iodine-labeled tracers. Clinical correlations improve strikingly when apparent free testosterone concentrations rather than total serum testosterone concentrations are used.     

Naltrexone effects on male sexual behavior, corticosterone, and testosterone in stressed male rats

Chronic physical or psychological stress disrupts male reproductive function. Studies in our laboratory have shown that stress by immersion in cold water (ICW) and by electrical foot shocks (EFS) has inhibitory effects on male sexual behavior; these effects do not seem to be mediated by an increase in corticosterone, nor by a decrease in testosterone. On the other hand, it is known that endogenous opioids are released in the brain in response to these same stressors; consequently, they could be participating in the impairment of sexual behavior, as well as in the changes in corticosterone and testosterone caused by stress. The aim of this study was to analyze the effects of the opioid antagonist naltrexone (NTX) on male sexual behavior, corticosterone, and testosterone in both stressed sexually experienced and naive male rats. Sexually experienced adult male rats were assigned to one of the following groups (n = 10 each): 1) control group, males without sexual evaluation; 2) control group, rats injected ip with saline, non-stressed; 3) control group, rats injected with NTX (3 mg/kg) non-stressed; 4) rats injected ip with saline, and stressed by EFS; 5) rats injected ip with NTX (1.5 mg/kg) and stressed by EFS; 6) rats injected ip with saline and stressed by ICW; 7) rats injected ip with NTX (1.5 mg/kg) and stressed by ICW; 8) rats injected ip with NTX (3 mg/kg) and stressed by ICW. Naive males were assigned to the same control groups but only stressed by ICW and the NTX dose used was 3 mg/kg. Injections were given 30 min before stress sessions. Stress was applied on 20 consecutive days. Male sexual behavior was assessed 15 min after EFS or 30 min after ICW, on days 1, 4, 8, 12, 15, and 20. Trunk blood was collected at the end of the experiments on day 20 of stress. Corticosterone and testosterone were evaluated by HPLC.Mount, intromission and ejaculation latencies were longer in control saline naive males compared to control saline sexually experienced males on the first day. NTX administration to control naive males caused a decrease in mount, intromission, and ejaculation latencies, as well as an increase in ejaculatory frequency/30 min, compared to control-saline only on day 1. Stressed naive males showed higher mount, intromission and ejaculation latencies, compared to control and stressed sexually experienced males, as well as comparable increase in corticosterone and decrease in testosterone plasma levels. NTX administration before exposure to stress prevented the modifications caused by stress in sexual parameters. Sexual behavior in control sexually-active males injected with saline or NTX was not modified. Saline stressed males showed the previously reported alterations in sexual behavior, as well as an increase in corticosterone and a decrease in testosterone plasma levels. Stressed males injected with NTX before exposure to stress showed no alterations in male sexual behavior. NTX in control non-stressed males did not modify corticosterone plasma levels, but did cause a significant increase in plasma testosterone. The increase in corticosterone and the decrease in testosterone due to stress, were attenuated with the opioid antagonist, both in naive and sexually experienced males. Prevention of ICW stress effects was more effective with higher doses of NTX (3 mg/kg). These data suggest that endogenous opioids could be participating in the effects caused by stress on male sexual behavior, corticosterone, and testosterone.     

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.     

Hormone-dependent aggression in male rats is proportional to serum testosterone concentration but sexual behavior is not

Male hooded rats were castrated and implanted with Silastic capsules (1.57 mm i.d.; 3.18 mm o.d.) having a testosterone-filled space 0, 7, 22, 60, or 90 mm long. All animals were returned to their original group cages for a three-week period to allow hormone concentrations and behavioral tendencies to stabilize. Each male was then housed with an intact female in a large cage. Aggression by the male toward an unfamiliar male was tested at weekly intervals for three weeks. Sexual behavior with an estrogen/progesterone-primed ovariectomized female was tested on each of the subsequent two weeks. Serum testosterone was measured during the following week. The frequency of aggression was correlated with serum testosterone concentration up to the normal level and did not increase with higher serum testosterone concentrations. In contrast, sexual behavior was virtually absent in animals with no testosterone replacement and normal in all other groups. These results demonstrate a clear dissociation in the dependence of hormone-dependent aggression and sexual behavior on serum testosterone concentration. In a male cohabiting with a female, sexual experience activates hormone-dependent aggression toward an unfamiliar male but the level of aggression that develops depends on the serum testosterone concentration in the resident male.     

Neonatal androgen influences sexual motivation but not the masculine copulatory motor pattern in the rat

Masculine sexual responses displayed by female rats, were compared to those of males. Twenty-five percent of females mounted and 19% showed intromission behavior, but none of them displayed the ejaculation pattern. Masculine sexual behavior was displayed in all stages of the estrous cycle. Accelerometric and spectrum frequency analysis of electrical signals generated by pelvic movements during mounting and intromission showed that these patterns were identical in both sexes excepting that mount duration in females was longer than in males. Neonatal androgenization of females increased the display of intromission patterns. Treatment of ovariectomized rats, androgenized or not, with either estradiol benzoate or testosterone propionate stimulated masculine sexual behavior. The ejaculatory pattern was only displayed by neonatally androgenized females. Mounting and intromission motor patterns of females under steroid treatment, and ejaculations of neonatally androgenized females, were similar to those of males. The results show that the organization of the movements involved in masculine sexual behavior in rats are identical in both sexes, thus suggesting that the neural circuits controlling these behaviors could be identical. Neonatal or postpubertal androgen in the rat influences the frequency with which male-like responses are displayed, but not their temporal (frequency, rhythm) or dynamic (acceleration, vigour) characteristics.     

Effects of prenatal antiandrogen treatment on masculinization and defeminization of guinea pigs.

Gonadectomized (gdx) guinea pigs which had received the antiandrogen flutamide prenatally were tested for female-typical and male-typical sexual behavior in adulthood. In tests for lordosis behavior, gdx males and females were injected with estradiol benzoate and progesterone. Prenatally flutamide-treated females showed a longer mean lordosis response than control females. This was true whether they were given either a high or a low dose of EB. No male ever showed a lordosis response. In tests for male-typical sexual behavior, gdx adult males were treated with testosterone propionate and tested with stimulus females. The prenatally flutamide-treated males showed significantly decreased levels of ejaculation, a lower intromission rate and a decreased percentage of mounts which included pelvic thrusts, when compared to control males. Mount rate and rate of pericopulatory behavior did not differ between the flutamide and control males. The fact that prenatal administration of flutamide increased female-typical behavior in adult females suggests that the female guinea pig is normally partially defeminized by androgens in utero. The male guinea pig appears to be resilient to attempts to block defeminization with prenatal antiandrogens. However, some aspects of masculinization can be blocked.