Restoration of sexual performance in old rhesus macaques paired with a preferred female partner

Experiments were undertaken to determine whether the decline in the ejaculation frequency of old male rhesus macaques is due to a decrease in physical capacity. In the first experiment, the capacity of old males to ejaculate in a series of biweekly tests was investigated. Six old (18–23 years) and six young (8– 12 years) male rhesus macaques were given 10-min tests of sexual behavior with nine different females chosen at random. The old males were also given 10-min tests with a preferred female, 1339. When the old males were tested with nine different females, their sexual performance (e.g., frequency of ejaculation) was significantly less than that of the young males, but their performance was comparable to that of young males in nine tests with female 1339. In a second experiment, the capacity of old males to show repeated ejaculations over a 3-hr period was tested. The same old and young males were given a 3-hr test with female 1339. The sexual performances (number of ejaculatory series completed and behavior displayed within each ejaculatory series) of the old males did not differ significantly from those of the young. Also, no significant differences in behavior were observed between young and old males during the first 10 min of the 3-hr tests. Our data show that the decline in the sexual performance of old rhesus males is not due to a decreased capacity to perform sexually or to physical debilitation.     

Female-female mounting among goats stimulates sexual performance in males

The hypothesis that female-female mounting is proceptivity in goats, in that male goats are aroused by the visual cues of this mounting behavior, was tested. Once a week, male goats were randomly selected and placed in a test pen in which they were allowed to observe one of six selected social or sexual stimulus conditions. The stimulus conditions were one familiar male with two estrous females (MEE); three estrous females that displayed female-female mounting (E(m)); three estrous females that did not mount (E(nm)); three non-estrous females (N(E)); three familiar males (M); and no animals in the pen (Empty). After 10 min, the stimulus animals were removed, and an estrous female was placed in the test pen with the male for a 20-min sexual performance test. During sexual performance tests, the frequencies and latencies of all sexual behaviors were recorded. This procedure was repeated so all males (n = 6) were tested once each test day, and all the stimulus conditions were presented each test day. This was repeated weekly until all males had been exposed to each stimulus condition. Viewing mounting behavior, whether male-female or female-female, increased the total number of sexual behaviors displayed, increased ejaculation frequency, and decreased latency to first mount and ejaculation, post-ejaculatory interval, and the interval between ejaculations. We conclude that male goats are aroused by the visual cues of mounting behavior, and that female-female mounting is proceptivity in goats.     

Copulatory behavior of sexually inexperienced male voles paired with proestrous females

The copulatory behavior in sexually inexperienced male voles aged 9-13 weeks old was observed under dim red illumination. Proestrous females were used as stimulus voles in copulatory behavior tests. A 30-min test session was recorded. All males showed at least one ejaculation within 30 min. In addition, the pattern of copulatory behavior in male voles was compared to that reported previously in male hamsters. The frequencies of mount, intromission and ejaculation in male voles were similar to that in male hamsters but there were significant differences in the latencies of mounting, intromission, ejaculation and post-ejaculation between the two species.     

Reversal of reproductive deficiency in the hpg male mouse by neonatal androgenization.

Some aspects of reproductive function in the GnRH-deficient hypogonadal (hpg) mutant mouse can be restored by transplanting normal fetal brain tissue containing GnRH cells into the central nervous system of adult hpg mice. However, hpg males showing physiological response to the graft fail to display sexual behavior and are infertile. We hypothesized that the reproductive deficit of these males is due to insufficient perinatal exposure to testicular androgens as a consequence of the GnRH deficiency. To test this hypothesis we androgenized hpg males by giving them neonatal injections of testosterone propionate (TP). Controls consisted of hpg males not androgenized neonatally and of normal males. All three groups received a TP implant in adulthood, and their copulatory behavior and reproductive capability were recorded. In addition, other hpg males, not androgenized neonatally, received fetal brain transplants containing GnRH neurons and were also tested for copulatory behavior and reproductive capability before and after receiving a TP implant. Three of 8 neonatally androgenized hpg males expressed the full repertoire of male sexual behavior, including intromission and ejaculation, and sired several litters. Three of 7 control hpg males that were not androgenized neonatally but received TP implants in adulthood also displayed mounting and intromission, but there was no evidence of ejaculation, and these males failed to impregnate normal females. Of the 8 hpg males that responded to a fetal transplant with testicular growth, only 1 displayed mounting behavior. However, when given a TP implant, 4 of 8 hpg males with grafts displayed mounting and intromissions.(ABSTRACT TRUNCATED AT 250 WORDS)     

Masculine sexual behavior in male and female rats following perinatal manipulation of androgen: Effects of genital anesthetization and sexual experience

Androgenized females, Day 1 male castrates, normal males, and normal females were tested for mounting behavior as adults following TP administration (1 mg/day). Genital anesthetization was used to eliminate all intromission and ejaculation behavior. Results showed that sexually-naive normal males and androgenized females mounted significantly more then Day 1 male castrates, while the Day 1 male castrates mounted significantly more than normal females. Sexually-experienced normal males and androgenized females displayed a significant facilitation of mounting behavior as compared to the sexually-naive animals. Tests of masculine copulatory behavior without genital anesthetization also were conducted with androgenized females and normal males. In these tests, androgenized females were indistinguishable from normal males in all aspects of the complete masculine pattern. The present results provide evidence that during perinatal development androgen acts directly on neural systems which will later regulate adult masculine sexual behavior.     

Serial copulatory behavior of male hamsters and rats

The copulatory behavior of mammalian males is generally characterized by the male's repeated approaches to and mounting of the female. The mounting behavior can lead to intromission, and after several intromissions, an ejaculation occurs. Following ejaculation, the male refrains from sexual activity for a period of time, the so-called "post-ejaculatory interval (PEI)". Most mammals will return to copulate again. Both male hamsters and rats were used and each animal performed five series of copulations with a proestrous female. From the 1st to 5th series of copulations the hamsters showed a shorter PEI than the rats. In addition, the PEI of the hamsters showed no change after each ejaculation, while the rats gradually showed a significantly increased PEI during the five series of copulations.     

Sex differences in the inhibition by ATD of testosterone-activated mounting behavior in guinea pigs

Adult male and female guinea pigs from a genetically heterogeneous stock were gonadectomized and tested for mounting behavior before and during various treatments with testosterone cypionate (TC) alone or in combination with an aromatase inhibitor, 1,4,6-androstatriene-3,17-dione (ATD). ATD was implanted subdermally in Silastic capsules (either 1 or 2 in females; 2 or 3 in males). In females 2 capsules of ATD completely blocked the behavioral effects of TC, and 1 capsule was an effective blocker in 58% of the females. The blocking effect was reversed by injection of diethylstilbestrol. In males, there was no measurable effect of ATD on mounting activity even when 3 capsules were implanted. Moreover, the TC induction of higher components of male sexual behavior (intromission and ejaculation) was also not impaired by ATD. Results are interpreted as indicating that either the process of male sexual differentiation or the male genotype eliminates the requirement for aromatization in androgenic activation of sexual behavior.     

Sexual behavior and serum hormone levels in aging rhesus males: effects of environmental change

Old (N = 9) and middle-aged (N = 9) rhesus males (Macaca mulatta) that were housed in the same type of home cage and the same room for several years were moved to a new location in an adjacent building. Their sexual behavior and hormone levels in the weeks preceding the move were compared to those after the move. The hypothesis that the nonspecific sensory stimulation provided by the move would increase levels of sexual behavior was not supported by the data. To the contrary, the percentages of tests with contacts, mounts, and penile erections, and the rate of contacting the female, decreased significantly for both old and middle-aged males. The intromission rate of middle-aged, but not of old, males also decreased. In consonance with previous findings, middle-aged males displayed significantly higher levels of sexual activity than did old males. The differences were observed both before and after the move. Serum testosterone levels did not differ between middle-aged and old males, and the move did not produce significant changes in testosterone levels. Serum cortisol levels were significantly higher immediately after the move (1 hr) but returned to premove levels the following day.     

Hormones and sexual behavior in relationship to aging in male rats.

To determine if the age-related decline in male sex behavior is correlated with hormonal factors, a longitudinal study was conducted. Sexually experienced males were given mating tests every 2 months from 7 through 27 months of age. To study possible relationships between changes in behavior and alterations in hormone levels, blood samples were taken before and after these bimonthly tests. At 23 months, cross-sectional studies were also conducted comparing results to those obtained in 5-month-old males. Significant changes in mating behavior first appeared at 11 months; mount latency, intromission latency, ejaculation latency, postejaculatory interval, and intercopulatory interval were increased. Similarly, detectable decreases in testosterone (T) also occurred at this age. A significant decline in luteinizing hormone (LH) was not seen until 19 months. Correlational analyses revealed small (r less than or equal to -0.29) but significant negative correlations between T and parameters of mating behavior with age. When each age was examined separately, no significant correlations appeared. Plasma T was not predictive of behavioral performance. At 23 months, cross-sectional studies revealed deficits in mounting and penile reflex behavior but ejaculatory reflex capacity was unimpaired. At 28 months, males were decapitated. Only T levels showed a significant effect of age; estradiol, prolactin, and LH were unaffected when compared to 5-month-old males. The data suggest that although there are small and significant negative correlations between circulating testosterone and parameters of mating behavior with advancing age, it is unlikely that the observed decline in testosterone is the primary cause of the age-induced behavioral deficits. It is likely that the major causal factor(s) involves non-hormone-dependent changes within the CNS.     

Prenatal stress reduces fertility of male offspring in mice, without affecting their adult testosterone levels

The male offspring of mice stressed by crowding during the final third of pregnancy showed reductions in sexual behavior and fertility. When paired with receptive females, their latencies to mount and to achieve intromission and ejaculation were greater than controls, and 30% of them failed to ejaculate in the 100-min test. When housed continuously for 4 days with females, 31% of them failed to impregnate their partners, compared with 4% of controls. The sexual receptivity of the untreated females paired with prenatally stressed males was not affected. Resting testosterone levels of prenatally stressed males did not differ from those of controls, and the pattern of rise and fall of testosterone during a 60-min interaction with a female showed only minor differences. The results suggest a central, rather than peripheral, mediation of the behavioral effects of prenatal stress.     

Effects of Eurycoma longifolia Jack (Tongkat Ali) on the initiation of sexual performance of inexperienced castrated male rats.

We studied the effects of Eurycoma longifolia Jack, commonly known as Tongkat Ali in Malaysia, on the initiation of sexual performance and the weights of sexual accessories in inexperienced castrated male rats. The doses of 200, 400 and 800 mg/kg body weight, which were extracted from E. longifolia Jack, were orally administered to the rats twice daily for 10 days prior to the tests and continued throughout the test period. Testosterone was used as a positive control after injecting 15 mg/kg daily subcutaneously for 32 days. Results showed that E. longifolia Jack produced a dose-dependent increase in sexual performance of the treated animals, but the E. longifolia Jack groups showed lower sexual performance in mounting, intromission and ejaculation than the testosterone group. Further results also showed that E. longifolia Jack promoted the growth of both ventral prostate and seminal vesicles as compared with the control, but the growth of sexual accessories at 800 mg/kg of butanol, methanol, water and chloroform fractions of E. longifolia Jack was less than that of testosterone treated group. The present study therefore gives further evidence of the folkuse of E. longifolia as an aphrodisiac.     

Female-typical sexual behavior of rhesus and defeminization by androgens given prenatally

Adult rhesus monkeys were observed in standardized tests for female-typical sexual and related social responses. In the first experiment reported, 7 castrated males and 5 spayed females were paired with each of 4 intact males on two occasions following intramuscular injection with estradiol benzoate (EB) (6 micrograms/kg X 14 days) and on two other occasions without such treatment. In tests without EB, males and females did not behave differently toward the intact male partners, and all responses were displayed at low frequencies. In tests with EB, females showed reliably higher frequencies than males of approaching, sitting close to, grooming, and soliciting, and they presented to a higher proportion of the male partner's sexual contacts. EB reliably increased the frequency of display of all of these same five responses in females but not in castrated males. The intact male partners displayed reliably fewer approaches, sexual contacts, mounts, intromissions, and ejaculations to castrated males than to spayed females regardless of estrogenization. In a second experiment 10 intact adult pseudohermaphroditic females and 6 intact control females were tested following EB injections with each of the same 4 intact males. Pseudohermaphrodites were experimentally produced by injecting pregnant females with either testosterone propionate (TP) or dihydrotestosterone propionate (DHTP). Pseudohermaphrodites, regardless of type of androgen used in their production, showed reliably fewer solicits than controls to male partners. Moreover, they displayed most of the other responses at lower average frequencies than controls. Frequencies of intromission and ejaculation by intact male partners were reliably lower with pseudohermaphrodites than with control females, but frequencies of approach, sexual contact, and mount were not reliably different. We conclude that in this testing and measurement situation male and female rhesus monkeys differ markedly in the degree of expression of female-typical sexual behaviors, and genotypic males are behaviorally less responsive to estrogens than females. Exposing genotypic females to androgens during fetal life decreases the expression of female-typical, estrogen-influenced responses, and the effect is most pronounced on those soliciting responses that subserve proceptivity.     

The reproductive--endocrine response of adult rams to sexual encounters with estrual ewes is season dependent

An experiment was conducted with four adult, sexually inexperienced Finnish Landrace rams during the ovine nonbreeding (July) and breeding (October) seasons to determine the influence of components of the rams' mating behavior on the secretion of luteinizing hormone (LH), follicle-stimulating hormone (FSH), prolactin (PRL), and testosterone. On four occasions in both seasons, blood was collected by jugular venipuncture at 20-min intervals during an 8-hr period while rams were (1) separated from, (2) observing with minimal direct physical contact, (3) mounting without intromission, or (4) mating estrous-induced ewes. In comparison with separation periods, mating activity in July was associated with increased mean LH (P less than 0.05) and testosterone levels and number of LH peaks, while in October, obvious increases were detected in only baseline LH levels (P less than 0.05). Circulating LH and testosterone levels either did not change (July) or were depressed (October) during the mounting and observation periods. FSH levels generally remained unaffected by engagement in the various sexual activities. Although a clear relationship between type of sexual activity and mean PRL levels was not observed in July, activities which appeared to involve the most physical exertion tended to be associated with much higher circulating PRL levels in October. These data suggest (1) the act of ejaculation is important in the induction of increases in LH and testosterone secretion that occur in rams in response to mating activity during the nonbreeding season and (2) excessively stressful sexual activities during the breeding season may alter the pattern of secretion of some reproductive hormones.     

Effect of age on the copulatory behavior of the male rat]

Fifteen male SPF Wistar-Imamichi rats, aged 10, 27 and 44 weeks, that had been raised in the authors' laboratory, were used for the observation of copulatory behavior. Each male was given the opportunity to mate with a proestrous female. During a two hour period, standard measures of copulatory behavior, e.g., mounting, intromission and ejaculation, were documented by a video recording. The following results were obtained; the number of ejaculations in 10-week-old rats, over a two hour period, was 6 to 8. Males showed a subsequent post-ejaculatory interval. The males aged 27 weeks performed 3 to 4 times during the first hour, and then refrained from sexual activity. The copulatory behavior in males aged 44 weeks declined, as compared with that of their 10 and 27 weeks old counterparts.     

Sexual experience affects reproductive behavior and preoptic androgen receptors in male mice

Reproductive behavior in male rodents is made up of anticipatory and consummatory elements which are regulated in the brain by sensory systems, reward circuits and hormone signaling. Gonadal steroids play a key role in the regulation of male sexual behavior via steroid receptors in the hypothalamus and preoptic area. Typical patterns of male reproductive behavior have been characterized, however these are not fixed but are modulated by adult experience. We assessed the effects of repeated sexual experience on male reproductive behavior of C57BL/6 mice; including measures of olfactory investigation of females, mounting, intromission and ejaculation. The effects of sexual experience on the number of cells expressing either androgen receptor (AR) or estrogen receptor alpha (ERα) in the primary brain nuclei regulating male sexual behavior was also measured. Sexually experienced male mice engaged in less sniffing of females before initiating sexual behavior and exhibited shorter latencies to mount and intromit, increased frequency of intromission, and increased duration of intromission relative to mounting. No changes in numbers of ERα-positive cells were observed, however sexually experienced males had increased numbers of AR-positive cells in the medial preoptic area (MPOA); the primary regulatory nucleus for male sexual behavior. These results indicate that sexual experience results in a qualitative change in male reproductive behavior in mice that is associated with increased testosterone sensitivity in the MPOA and that this nucleus may play a key integrative role in mediating the effects of sexual experience on male behavior.     

Aphrodisiac activity of Butea frondosa Koen. ex Roxb. extract in male rats.

In the present study, the aphrodisiac activity of Butea frondonsa Koen. ex Roxb (Papillionaceae) bark extract was investigated. The extract (400 mg/kg body wt./day) was administered orally by gavage for 28 days. Mount latency (ML), intromission latency (IL), ejaculation latency (EL), mounting frequency (MF), intromission frequency (IF), ejaculation frequency (EF) and post-ejaculatory interval (PEI) were the parameters observed before and during the sexual behavior study at day 0, 7, 10, 14, 21, and 28. The extract reduced significantly ML, IL, EL and PEI (p < 0.05). The extract also increased significantly MF, IF and EF (p < 0.05). These effects were observed in sexually active and inactive male rats.     

Sexual performance of twin ram lambs and the effect of number and sex of contemporary siblings

The objectives of this investigation were to determine the degree of correspondence in the sexual performance of twin male sheep and to compare the sexual performance of ram lambs born co-twin to another male (M-M), co-twin to a female (M-F) and as single (S) offspring. Individual ram lambs (N=117), including 13 M-M twin sets, were exposed to four estrous ewes for 30 min at 7-day intervals over a 4-week period at 8 to 9 months of age.Frequencies of ejaculation (serving capacity) and mounts without ejaculation were recorded. M-M males averaged 2.9 ejaculations and 13.1 mounts per test. Individuals within 9 of the 13 M-M twin sets (69%) differed by an average of 0.5 or fewer ejaculations per test. Although variability within M-M twin sets was very low, variability between the 13 M-M twin sets was also low (coefficient of variation=10.6%). Consequently, frequencies of both ejaculation and mounting (without ejaculation) within the 13 twin sets were not correlated (P=0.50 and P=0.10, respectively). When the progeny of individual sires were compared, mounting frequencies were correlated (P<0.02) but not ejaculation rates (P=0.72). M-M, M-F and S ram lambs did not differ for either ejaculation frequency (P=0.26) or mounts without ejaculation (P=0.98). It was concluded that the sexual performance of related individuals is likely to be very similar and that the number and sex of contemporary siblings does not necessarily influence rates of mounting and ejaculation.     

Sexual deprivation and its influence on testosterone levels and sexual behavior of old and middle-aged rhesus males

After approximately 6 mo without access to a receptive female, eight old (19 to 25 yr) and eight middle-aged (9 to 15 yr) males were given nine daily 10-min tests of sexual behavior with receptive females. Three ovariectomized, estrogen-primed females served as partners. Blood samples were taken from the males at 0900 and 2100 h on 2 consecutive days before and after the series of nine behavioral tests. Serum levels of testosterone (T) were measured by means of radioimmunoassay. There were no significant differences between serum T levels after 6 mo of sexual deprivation and after the nine tests of sexual behavior, nor did serum T levels differ between middle-aged and old males. Serum T levels were significantly higher in the 2100-h samples than in the 0900-h samples for both groups. The nocturnal increases in serum T, both absolute amounts and percentages of increase, did not differ between middle-aged and old males. Repeated daily testing had little effect on the major components of male sexual behavior. Middle-aged males outperformed old males; middle-aged males had higher rates of contracting the female, mounting and intromitting. They ejaculated earlier and had a greater percentage of tests with ejaculations than did old males.     

Effects of aqueous extract of Alpinia calcarata rhizomes on reproductive competence of male rats

This study examined the effects of rhizomes of Alpinia calcarata Roscoe (Zingiberaceae) on male sexual competence and fertility, using a hot water extract (HWE) and rats. Different doses of HWE (150, 250 and 500 mg/kg) were orally administrated to male rats and their sexual behaviour was monitored (for 15 min) 3 h later using receptive females. Fertility was determined in a separate group (with the highest dose) using a noncompetitive copulation test. In the sexual behaviour study, the HWE impaired the number of rats ejaculating and markedly prolonged the latency for ejaculation. Further, the number of rats mounting and intromitting, and the latencies for mounting and intromission were inhibited. Collectively, these observations indicate a strong aphrodisiac action. The other parameters remained unchanged indicating non-impairment in libido, sexual arousability, sexual vigour and sexual performance or penile erectile ability. However, a slight impairment was evident in sexual motivation (with the highest dose) in a partner preference test. In the fertility test, HWE induced profound oligozoospermia but fertility was uninhibited. The highest dose of HWE also elevated the serum testosterone level and the number of spontaneous penile erections rapidly and markedly. Further, the HWE was nontoxic. It is concluded that A. calcarata rhizomes possess a strong and safe oral aphrodisiac activity.     

Male Post‐Ejaculatory Mounting in the Ring‐Tailed Lemur (Lemur catta): A Behavior Solicited by Females?

Male mate guarding can take many forms but often involves aggression toward male conspecifics and continued proximity with a female. This study describes a previously undocumented behavior in a promiscuous primate, the ring‐tailed lemur: post‐ejaculatory (PE) mounting. PE mounting was documented across eight mating seasons in a ring‐tailed lemur colony on St. Catherines Island (SCI), USA. During PE mounting, a male remounts a female following ejaculation and clasps her midsection as if to mate again, but copulation does not occur; males showing this behavior typically lack erections, and their mounts show an absence of penile intromission and rhythmic thrusting. Male PE mounting was more common among males mating earlier in the queue, and when PE mounting occurred, it accompanied mate guarding. Four non‐mutually exclusive hypotheses to explain PE mounting were evaluated as follows: (1) gaining additional copulations, (2) prevention of re‐mating, (3) lengthening sperm residence time, and (4) re‐mounting as a function of female proceptivity. Male PE mounting did not aid males in gaining additional copulations nor did PE mounting prevent females from mating with new males. Equivocal support was found for Hypothesis 3: although there was much overlap in copulatory plug residence times for males who did and did not show PE mounting, one‐third of males who practiced PE mounting had plug residence times of 2 h or more, much longer than that of males who did not show PE mounting. PE mounting may therefore be related to increased plug residence time, which may provide an advantage to males in sperm competition. Strong evidence was found in support of Hypothesis 4: males overwhelmingly performed PE mounts in response to continued female sexual presentations, suggesting that females can solicit this male behavior. Females consequently exercise an even greater degree of control over males than was previously realized in this ‘female dominant’ primate.