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PubMed1975

Heterosexual copulatory patterns in stumptail macaques (Macaca arctoides) and in other macaque species.

A comparison of the mating behavior patterns of several macaque species reveals that the mating behavior of Macaca arctoides exhibits several unique features. The laboratory groups of stumptail monkeys observed had exceptionally long single-mount copulations characterized by a large number of pelvic thrusts, a slow thrusting rate, and an unusually salient male orgasmic pattern (characterized by body rigidity followed by body spasms and a typical facial expression and vocalization). The frequency with which the copulation culminates in ejaculation is unusually high, and copulating stumptails generally manifest "tieing" in a genital lock after ejaculation.

Animals↗
PubMed1977

Sexual behavior of captive orangutans.

Opposite-sex pairs of orangutans were tested for sexual behavior during the intermenstrual period of the female. The male orangutan was the primary initiator of sexual interactions and initiated copulation forcefully on a daily basis, irrespective of female resistance. However, although single copulations occurred daily, copulations beyond the first occurred most frequently during midcycle. Other evidence of cyclicity in behavior was the midcycle decrease in female avoidance of the male and increased grooming, proceptivity, and masturbation by the female. Comparative analysis suggests that differences in sexual cyclicity among the great ape species are related to interspecies differences in sexual assertiveness of males and females. Sexual activity in the cycle is relatively brief when the female controls mating, more prolonged when the male is in control. This finding in man's closest taxonomic affiliates suggests that similar social factors may also influence the distribution of sexual interactions in the human cycle.

Animals↗
PubMed1994

Sexual behavior, sexual swelling, and penile evolution in chimpanzees (Pan troglodytes).

Functional relationships between the penis, vagina, and cervix during copulation in the chimpanzee were studied. In 11 adult males, penile length during full erection ranged from 10.0-18.0 cm (mean +/- SD = 14.4 +/- 2.02). In 19 parous adult females examined during the early follicular phase of the cycle, or during lactation, vaginal depth (from the introitus to the os cervix) ranged from 9.8-16.5 cm (mean +/- SD = 12.6 +/- 1.69). However, when the sexual skin was maximally swollen, vaginal depth increased by up to 52% in some cases and ranged from 15.2-20.1 cm (mean +/- SD = 16.9 +/- 1.68). Under such conditions males vary in their ability to achieve maximal depth of intromission. Observations made on 6 females after natural matings revealed that in some cases males had deposited copulatory plugs in contact with the cervix, while in others plugs were lower down in the vagina. Direct observations under fluoroscopy using an artificial "penis" loaded with radio-opaque medium showed that the filiform tip can make contact with the os cervix. However, expulsion of radio-opaque medium under these conditions failed to demonstrate any immediate transfer of fluid through the cervix into the uterus. These studies indicate that, aside from its functions as a visual signal, the female chimpanzee's sexual skin swelling adds considerably to the distance males must negotiate during copulation to place spermatozoa at the cervical os. Evolution of the male's elongated, filiform penis may therefore be the result of sexual selection, to negotiate the long vagina of the female and to penetrate copulatory plugs deposited during previous copulations.

Animals↗
PubMed1995

Opioid antagonists and the sexual satiation phenomenon.

This study evaluates the effects of the IP injection of naloxone (0.3, 3 and 30 mg/kg) and naltrexone (0.2, 2 and 20 mg/kg) on the sexual satiation phenomenon. It was found that both antagonists exert a dose-based biphasic effect on the proportion of sexually exhausted rats displaying copulation. The intermediate doses of both opioid antagonists were more effective than the low and high doses in increasing the percentage of animals engaged in copulation. The analysis of the specific sexual behaviour parameters revealed that naloxone produces a slight inhibitory effect at the lowest dose, evidenced as an increase in the intromission number. The higher doses of this compound facilitated copulation reflected as a shortening of the ejaculation latency and the interintromission interval (III) and an increase in the copulatory rate. Naltrexone treatment had only facilitatory effects at the lower doses by reducing the III. The higher doses of naloxone (3 and 30 mg/kg) and the intermediate dose of naltrexone (2 mg/kg) decreased the spontaneous ambulatory behaviour of sexually satiated rats without impairing sexual behaviour execution. Data suggest a participation of the endogenous opioid systems in the sexual inhibition resulting from sexual exhaustion.

Animals↗
PubMed1995

Effects of morphiceptin in the medial preoptic area on male sexual behavior.

Morphiceptin, a selective mu opioid agonist, injected into the medial preoptic area (MPOA), delayed the onset of copulation in male rats, but did not affect genital reflexes, sexual motivation or general motor activity. In a dose-dependent manner, morphiceptin (100 ng and 1000 ng) injected into the MPOA increased mount and intromission latencies. Similar injections of morphiceptin into the ventromedial hypothalamus had no effect on any parameter of copulation. The increase in copulatory latencies following the injection of the highest dose of morphiceptin was blocked by pretreatment with the opioid antagonist naloxone. In the X-maze task, morphiceptin had no effect on sexual motivation, as measured by the percentage of trials on which the male chose the female's chamber, but it increased the number of trials in which the subject did not select a chamber within 60 s and the latency to the female the first time he chose her chamber. Similar to the copulation task, the mount and intromission latencies were also increased in the X-maze, after the male reached the female. Morphiceptin in the MPOA had no effect on ex copula genital reflexes, tested in restrained supine males, or on motor activity, tested in a grid box. These results suggest that morphiceptin disrupts either the specific copulatory somatomotor pattern or a more general motivational component.

Analgesics↗
PubMed1976

Interactive effects of brain catecholamines and variations in sexual and non-sexual arousal on copulatory behavior of male rats.

In pargyline pretreated male rats, an intraventricular 6-hydroxydopamine procedure which resulted in subtotal brain catecholamine (CA) depletion produced a mild defict in copulatory behavior followed by rapid recovery. Challenges employed to study the behavioral capacities of these 'recovered' animals revealed: (1) a heightened sensitivity to acute treatment with the CA synthesis inhibitor alpha-methyl tyrosine (AMT) as reflected in a reinstatement and exaggeration of the original copulation deficit; (2) a greater dependence on the sexual eliciting properties of the female, since abolishing her soliciting behavior also reinstated and exaggerated the sexual dysfunction; and (3) a pattern of behavioral impairment indicating increased difficulty in both initiating sexual activity and maintaining copulatory performance. Furthermore, in males not copulating after 6-OHDA/AMT treatment, copulation could easily be induced by the simple application of a non-specific activating stimulus. On the basis of these data and parallel findings reported for other behaviors, we have concluded that: (1) both the initiation and maintenance of copulatory behavior in the male rat is the part dependent on normal functioning in one or more of the brain CA-containing systems; and (2) this copulatory deficit is symptomatic of a broader functional impairment reflecting reduced behavioral responsiveness to stimuli that normally elict appetitive or approach responses but not to stimuli requiring more automatic, inhibitory responses.

Animals↗
PubMed1995

Neurochemical correlates of sexual exhaustion and recovery as assessed by in vivo microdialysis.

The extracellular levels of the dopamine (DA) metabolites dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) and the serotonin metabolite 5-hydroxyindoleacetic acid (5-HIAA) in the medial preoptic area (MPOA) of male rats were monitored during unrestricted copulation, the ensuing state of sexual refractoriness and the resumption of mating activity. MPOA dialysates were collected from the same animal during four consecutive days. In the first day the subjects were allowed to copulate until reaching a satiation criterion. That was associated with a marked increase in the dialysate levels of the three metabolites assessed. During the next two days the animals remained sexually inactive when exposed to receptive females. Their basal levels of DOPAC and HVA were elevated, whereas those of 5-HIAA remained as low as in the first session. During the non-mating exposure to receptive females there were only minor changes in the three metabolites. By the fourth day, just before the animals resumed copulation, the basal levels of the DA metabolites, especially HVA, had decreased to values closer to those found in the first day. When they mated again to exhaustion the levels of DOPAC, HVA, and 5-HIAA increased as in the first session. The neurochemical changes found during the intervening state of sexual inactivity (i.e. increased levels of DA metabolites) are reminiscent of the effects of DA receptor blockers, which suggests a possible neurochemical mechanism for sexual refractoriness.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1995

Dopamine release in the medial preoptic area during male copulatory behavior in rats.

In vivo microdialysis was employed to measure the extracellular concentrations of dopamine (DA) in the medial preoptic area (MPOA) of rats during male sexual activity to look for a correlation with sexual activity. During copulation, the concentration of DA in the MPOA was significantly increased. A significant difference was detected in changes of DA between copulators and non-copulators. These findings were consistent with the assertion that DA neuron activity in the MPOA facilities male copulatory behavior.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1983

Menstrual cycle patterns of hormones and sexual behavior in gorillas.

Oppositely sexed pairs of gorillas were tested behaviorally during the menstrual cycle to determine the relationship between hormone concentrations of the female and the frequency of sexual activity by the pair. Five females were tested individually during two cycles with each of two males, but serum samples for hormone assay were obtained from each female only during the first cycle of testing. There was no clear relationship between hormones and behavior for the single cycle in which the serum samples were obtained, with the exception that no copulations occurred after the early luteal phase, when progesterone was greater than 5 ng/ml. Normalized behavioral data from all four test cycles for all pairs suggested that female-solicited copulations were restricted primarily to the periovulatory period. Male sexual initiative (by one of the males) accounted for most copulations temporally dissociated from the periovulatory period. Normalized hormone data for all of the females suggested that (1) attractivity was associated with estradiol concentrations during the follicular phase, (2) proceptivity with estradiol and testosterone at midcycle, whereas (3) receptivity was not associated with hormone patterns or cycle phase. The data suggest that hormones are one of several variables that contribute to the regulation of sexual behavior in gorillas.

Animals↗
PubMed1992

Erectile function and bulbospongiosus EMG activity in estrogen-maintained castrated rats vary with behavioral context.

Electromyographic (EMG) activity in the bulbospongiosus muscles (BS) was recorded to monitor potential castration-induced alterations in muscle activity during copulation and reflexive erections. EMG recordings were made from intact male rats and from castrated rats maintained from 7 to 50 days on estradiol benzoate (300 micrograms/day) or testosterone (200 micrograms/day). Despite a 40-50% postcastration reduction in the weight of the BS and accessory sexual glands in estrogen-treated rats, the pattern of EMG activity during copulation was similar across groups. In estradiol-treated males, the EMG burst frequency during mounts and burst duration during intromissions exceeded the parameters of intact males and of castrated males maintained on testosterone. Between intromissions, and following ejaculatory patterns, estrogen-treated males displayed spontaneous muscle bursts accompanied by visually confirmed erection of the glans penis, but these males quickly lost the capacity for reflexive erections. These data demonstrate that despite castration-induced atrophy of the penile muscles and, presumably, their spinal motor nuclei, the motor output to these muscles is maintained following androgen removal. The capacity for substantial penile erection is retained during copulation long after reflexive erections have diminished.

Androgens↗
PubMed1983

The effects of testosterone and its metabolites on sexual behavior and morphology in male and female Japanese quail.

Adult Japanese quail are sexually dimorphic. Even when implanted with testosterone (T), ovariectomized females fail to copulate and their cloacal glands are smaller than those of males. This may be due to a reduced capacity of the females to transform testosterone into active metabolites (estradiol-17 beta and 5 alpha-dihydrotestosterone). Indeed, in the male quail, estradiol-17 beta (E2) activates copulation whereas 5 alpha-dihydrotestosterone (5 alpha-DHT) activates crowing, strutting and the development of the cloacal gland. To test this hypothesis, we studied the effects of in vivo treatments of male and female quail with the different T-metabolites. Forty-one castrated male and female quail were implanted with subcutaneous silastic implants of T, 5 alpha-DHT, E2 and E2 in combination with 5 alpha-DHT. When implanted with these metabolites, females failed to copulate and their cloacal glands remained less developed than those of males. Sexual differences in behavior and morphology thus cannot be entirely explained by sexual dimorphism of the metabolism.

Animals↗
PubMed1986

Preoptic and midbrain control of sexual motivation.

In a testing arena where a male rat can choose to spend time (and mate with) a sexually receptive female or choose a non-receptive female, a sexually motivated male will prefer the sexually receptive female and a decrease in preference for the receptive female can be said to reflect a decrease in sexual motivation. We have used a preference test to study the effects of castration and brain damage on sexual motivation. In neurologically intact males castration virtually eliminates copulation and decreases preference for a receptive female; copulation and preference are restored by replacement therapy with testosterone. Lesions of the medial preoptic area (MPOA) and lesions of the dorsolateral tegmentum (DLT) of the midbrain abolish copulation and decrease preference for a sexually receptive female. In lesioned males preference declines even further as testing is extended over a span of several months and is not affected by either castration or replacement therapy with testosterone. It seems likely that, at least in part, castration and brain damage decrease mating by decreasing sexual motivation. The MPOA and DLT are connected by axons running through the medial forebrain bundle, and we speculate that sex hormones may work on cells in the MPOA to increase sexual motivation and behavior, perhaps by altering the activity of axons projecting to the DLT which are principally involved in the mediation of sexual reward or "pleasure".

Animals↗
PubMed1986

Effect of flutamide (an antiandrogen) and diethylstilbestrol on the reproductive behavior of Japanese quail.

Three experiments were conducted in order to investigate the role of brain androgen and estrogen receptors in sex hormone activated male reproductive behavior in Japanese quail. In Experiment 1, castrated male quail were injected with oil, testosterone propionate (TP), flutamide (FLUT), an androgen antagonist, or TP+FLUT. Males given TP+FLUT, compared with birds receiving TP alone, strutted much less and had smaller proctodeal (foam) glands. Copulation was reduced by FLUT only on the last test day and only on one measure (number of head grabs + mounts). These results suggest that binding of testosterone or one of its metabolites to an androgen receptor is part of the mechanism of TP activated strutting, and therefore that central nervous system androgen receptors are involved in a male reproductive behavior pattern. In Experiment 2, castrated male quail were injected with oil, with 50 micrograms estradiol benzoate (EB), or with 25, 50 or 100 micrograms diethylstilbestrol (DES), a synthetic estrogen that does not bind to androgen receptors. EB but not DES activated copulation to a significant extent. In Experiment 3 male and female quail with photically regressed gonads were given intraperitoneal Silastic implants of DES, estradiol (E) or cholesterol. DES was highly effective at activating male-typical copulation in males and receptivity in both sexes. Thus hormonal interaction with estrogen receptors alone is sufficient for the activation of male-typical as well as female-typical copulatory behavior in this species.

Anilides↗
PubMed1988

Behavioral aspects of puberty in group-living stumptail monkeys (Macaca arctoides).

Behavioral changes before and around the time of puberty were studied in a longitudinal manner in male and female stumptail monkeys. Around the time of testicular descent (mean age: 3.3 years) males started to become more aggressive towards adult males. Within two years following testicular descent males rose in rank with the support of others and reached stable (sub)top positions in the dominance hierarchy. In the female rank-stabilization took place gradually between one year before and two years after first ovulation (mean age: 3.7 years). Copulatory activity began about two (in females) to two-and-a-half years (in males) before reproductive capacity was attained. Female copulatory activity began to rise about six months before first ovulation, when they started to copulate with adult males. In males copulatory frequency rose sharply between six and twelve months prior to testicular descent. Until a few months after testicular descent males could copulate openly in the group without interruption; from about 1 year following testicular descent virtually all copulations had to take place surreptitiously to avoid interruption by higher ranking adult males. It is postulated that this decreasing tolerance of adults may contribute to the process of peripheralization and migration of young adult males which occur in free ranging macaque groups.

Aggression↗
PubMed1990

The effect of time of day on sperm competition and male reproductive success in laboratory rats.

The study was designed to test the hypothesis that siring success of male rats depends on when during the receptivity period the matings occur. In Experiment 1, females were mated with pairs of males differing in coat colour genetic marker. The males copulated with the female successively, either about 1 hour apart at dusk (schedule AA) or about 1 hour apart around midnight (BB) or one at dusk and the other around midnight (AB). The males mating first had lesser siring success under the schedule AB than under the other two schedules. In Experiment 2, females were mated under the same regimen as in Experiment 1. One male of each competing pair had its spermatozoa labeled by 3H-thymidine. The proportions of spermatozoa of the labeled males were identified in samples from uterine horns and oviducts. Balanced contributions of both males were recorded in uterus in all groups. No definitive conclusion concerning oviductal sperm composition could be reached. In both experiments, night-mating males copulated more quickly. It is suggested that copulation at about midnight is advantageous in intermale reproductive competition and that the function of the diurnal variation in the speed of male sexual behaviour might be clarified on this ground.

Animals↗
PubMed1991

Inhibition of infanticide in male Swiss mice: behavioral polymorphism in response to multiple mediating factors.

The socio-sexual factors mediating the inhibition of pup-killing in previously infanticidal Swiss Webster male mice (Mus domesticus) were examined. As reported in other studies, postmating co-habitation (i.e., physical contact) with a female during pregnancy suppress pup-killing but the present experiments also showed that several factors are implicated in this phenomenon, namely: 1) Postcopulatory sensory contact (i.e., behind a wire-mesh partition) with the pregnant mate was sufficient to inhibit infanticide virtually in all the subjects. Copulation seems to function as a "primer," but cues, most likely of an olfactory nature, emitted by pregnant mate induce paternal behavior in the stud male. In fact, either copulation followed by sensory contact with a nonpregnant mate (abortion was induced) or sensory contact without copulation with a pregnant female did not suppress pup-killing in the majority of cases. 2) Mating, per se, is capable of inhibiting infanticide in a minority of males. 3) Physical contact with a parturient female (impregnated by another male) at the time of pup delivery inhibited infanticide in approximately 40-50% of males. The data essentially show that, in a house mouse population, there is a behavioral polymorphism in response to the coexisting multiple mechanisms which mediate the inhibition of infanticide.

Animals↗
PubMed1994

Effects of chronically high doses of the anabolic androgenic steroid, testosterone, on intermale aggression and sexual behavior in male rats.

To determine if chronic exposure to high doses of anabolic androgenic steroids (AAS) increase aggression and sexual activity in gonadally intact rats, we administered SC injections of testosterone propionate (TP: 1 mg) or propylene glycol (PG: as a vehicle control) three times per week for 10 consecutive weeks. Weekly tests for male copulation were conducted by pairing each male with a sexually receptive female in a glass arena and recording various parameters of copulation. Chronic treatment with TP did not alter any parameter of male copulation including ejaculation and post ejaculatory interval. Sexually experienced males were tested once per week for intermale aggression in a neutral environment. For aggression tests, each experimental animal was placed into an arena with an opponent male for 15 min. The opponent, a gonadally intact male, was used only for the purpose of the aggression test. Frequencies of dominance, submissive, threat, and fight postures, as well as approaches were scored for each animal. TP-treated males did not differ in body weight from PG-treated males, suggesting that the increased aggression was not due to increased body mass. The results of this study show that chronic exposure to the anabolic androgenic steroid, testosterone, potentiates male aggressive response patterns but does not alter male sexual behavior or body weight.

Aggression↗
PubMed1981

Copulatory behavior and sexual reflexes of male rats treated with naloxone.

Two experiments explored a potential role for endogenous opiates in the regulation of sexual behavior of male rats. Specifically, we questioned whether such opiates regulated the refractory period following ejaculation during copulation, or the latency period for the evocation of penile reflexes (erections, cups, and flips) from supine males. Animals were injected IP with 15-45 mg/kg naloxone hydrochloride 30 min prior to the start of reflex testing, and with 7.5-45 mg/kg naloxone hydrochloride 30 min before testing for copulation. Naloxone resulted in a small but reliable decrease in the number of penile flips. Reflex latency and other measures of penile reflexes were unaffected. At all doses used, naloxone significantly prolonged the postejaculatory refractory period, and there were no other effects on copulation.

Animals↗