Behavioral and physiological evidence of sexual climax in the female stump-tailed macaque (Macaca arctoides).

Intense tonic/clonic uterine contractions and sudden increases in heart rate coincided with the behavioral homolog of a male ejaculatory response (minus seminal emission) in a normal female stump-tailed macaque engaged in homosexual mounting episodes. The behavioral patterns were also observed in four of ten females during 5 to 40 percent of heterosexual copulations. These observations demonstrate the existence of an orgasmic response in a nonhuman primate.

Anosmia in male rhesus monkeys does not alter copulatory activity with cycling females.

Three adult male rhesus monkeys were tested daily with intact adult female partners over the course of four or five mentstrual cycles. The males were made permanently anosmic by chemical ablation of the olfactory epithelium after the second or fourth cycle was completed. All males continued to display typical cycles of copulation with their partners after the anosmia procedures, with the shortest latencies to ejaculation occurring during the periovulatory phase of the partner's ovulatory cycle. Hence, female attractivity and cyclic copulatory performance of rhesus monkeys are not dependent upon olfactory signals.

Pentobarbital inhibition of progesterone-induced behavioral estrus in ovariectomized guinea pigs.

Administration of pentobarbital inhibits the facilitatory effects of progesterone on the release of gonadotropins. In this experiment facilitatory effects of progesterone on lordosis behavior in guinea pigs were examined with pentobarbital anesthesia. Two major animal groups were subjects: one was short-term ovariectomized (2 weeks) and the other was long-term ovariectomized (several months). All animals received estradiol benzoate (6.6 mug s.c.) followed by progesterone (0.4 mg s.c.) 40 h later. Lordosis behavior was induced by the manual stimulation method of Young et al.29 Sodium pentobarbital (30 mg/kg) was injected 8,4 or 2 h before, simultaneously or 1, 2, 6, or 7 h after progesterone. Animals which received pentobarbital slept for 4.5-5 h with subsequent drowsiness for an additional 0.5-1 h. Pentobarbital injections given 8 h before progesterone had no effect on latency to the first lordosis or on other parameters of estrous behavior. However, pentobarbital delayed the onset of heat in estrogen treated ovariectomized guinea pigs when given 4 h before, 2 h before, or simultaneously with progesterone. The delay was directly related to the length of time the animals remained asleep after the progesterone injection, since estrous behavior was invariably displayed with the latency of controls after the animal awoke. Moreover, in animals which were awake for 1-2 h immediately after the progesterone injection before receiving pentobarbital, the latency of recovery from anesthesia to the first display of lordosis was about 1-1.5 h shorter than in the other pentobarbital groups. In contrast to the latency effects of pentobarbital, the duration of heat was unaffected by the anesthetic for all groups mentioned. In animals which received pentobarbital after they were already in heat, pentobarbital injection terminated heat and abolished it completely, since lordosis behavior was not displayed in the hours after recovery from anesthesia. Gross hypothalamic uptake of progesterone was not influenced by pentobarbital administration. Thus, it is tentatively concluded that an incubation period is necessary for progesterone to mediate the display of estrous behavior in the guinea pig in addition to the time necessary for neural uptake. The way in which pentobarbital interferes with the period of progesterone incubation is not currently known.

The effect of estradiol and progesterone on the sexual behavior of ovariectomized mares.

Daily treatment (5 days) with estradiol resulted in increased levels (p less than 0.05) of proceptive behavior in ovariectomized as compared to control mares (N = 8 per treatment) within 4 hr of injection and for the 4 subsequent days. Ejaculations occurred more often (p less than 0.05) in estrogen-treated mares on days 2-5, but the number of precopulatory investigations by the stallions was not altered. Progesterone treatment resulted in an absence of sexual behavior except in one mare on Day 1. Control mares exhibited varying levels of sexual interest. The concurrent administration of estradiol and progesterone produced a biphasic effect on proximity-related behaviors. Proximity behaviors were initially (Day 1) greater and subsequently less in the group treated with both hormones than in the group treated with estradiol alone. Injections of free estradiol resulted in a shorter latency to effect for two measures of proceptivity than did injections of estradiol benzoate. A dose response test for progesterone showed no effect with 0, 1, or 10 mg, but 100 mg was inhibitory (p less than 0.05). These results demonstrated that within 4 hr estradiol stimulated, while progesterone inhibited estrous behavior in ovariectomized mares and that concurrent administration of estradiol and progesterone produced a biphasic effect, first enhancing, then suppressing some aspects of the estrous response. The relatively short latency to action of all treatments and the biphasic effect of concurrent estradiol and progesterone may be attributable to low level, endogenous hormones.

Effect of amygaloid lesions on gonadal maturation in male and female ferrets.

Two experiments were performed to determine whether the amygdala is involved in theregulation of gonadal maturation in the ferret. In an experiment with prepuberal males it was found that testicular and epididymal wieghts, seminiferous tubule diameters, Leydid cell number, and ratings of spermatogenic development were the samein animals autopsied 4 wk after either the placement of a platinum-elctrode lesion in the amygdala or a sham operation. Testosterone concentrations both in testis and in blood tended to be lower, and body growth was significantly retarded in males with amygdaloid lesions. In a second experiment with prepuberal females it was found that the first estrus occurred significantly earlier in ferrets that had received amygdaloidlesions than in sham-operated controls. Neither body growth nor fertility of femaleswas affected. These findings suggest that the amygdala exerts an inhibitory influence on the hypothalamic mechanism which controls the secretion of gonadotropins required for initial estrus in female ferrets, but not for the initail masturation of the testes in males.

Peer and maternal influences on the expression of foot-clasp mounting by juvenile male rhesus monkeys.

The display of adultlike foot-clasp mounts by male rhesus monkeys occurs during the 1st year of life in animals reared with their mothers in social groups where peer interaction is possible 24 hr per day. In contrast, this form of mount is rarely displayed if infants are separated from their mothers at 3 months of age and allowed daily .5-hr periods for peer interaction. To distinguish between maternal and peer access-time influences upon the development of this response, we housed rhesus monkeys with their mothers and allowed either .5-hr or 24-hr daily access to peers in the presence of their mothers during the 1st year of life. Male infants restricted to .5-hr periods with peers rarely or never foot-clasp-mounted peers, although 3 of 6 males foot-clasp-mounted their mothers. In contrast, males given 24-hr access to peers regularly mounted peers using the foot-clasp mount. Males from the 2 groups did not differ in total frequencies of all mount types displayed, only in the display of foot-clasp mounts. After maternal separation at the end of the 1st year, rearing effects on the display of mounting persisted into the 2nd year. Males that received 24-hr daily peer access during the 1st year continued to foot-clasp-mount peers whereas .5-hr males failed to do so, indicating that the experience of mounting one's mother with the adult posture was not sufficient to support peer-oriented foot-clasp mounting at a later age. In addition to deficits in peer-oriented foot-clasp mounting. .5-hr infants displayed higher frequencies of threat and withdrawal behaviors to peers and presented to peers less frequently than did infants from the 24-hr rearing condition. These results contradict a motor deficiency hypothesis to account for the rare display of foot-clasp mounts to peers by males receiving .5-hr daily access to peers during the 1st year of life. Instead, data support the view that .5-hr animals either failed to develop positive response patterns necessary for the execution of the foot-clasp mount, or learned negative patterns of social interaction that prevented the display of this cooperative behavior.

Assessment of the sexual behavior of pregnant mares.

Pregnant mares (N = 12) were observed with a stallion from early gestation until parturition for sexual behavior. Observations were conducted for 20 min per day for 5 days each month from September until July. No mares exhibited full estrus and no intromissions or ejaculations occurred at any time during the study. Social interactions such as male approach and female/female mutual grooming occurred with greater mean frequency or duration in some months of spring and fall than in winter months. (P less than 0.05). None of the recorded behaviors differed by month of gestation. In a comparison of the behavior of diestrous and pregnant mares in harem groups, no estrous behavior occurred and no differences in social interactions were found. Although progesterone may be sufficient to cause the absence of sexual behavior in diestrous mares, another estrous-inhibiting substance may be present during pregnancy at times of high estrogen and low progesterone.

Social influence on the display of sexually dimorphic behavior in rhesus monkeys: isosexual rearing.

Groups containing 5 or 6 infant rhesus monkeys and their mothers were formed when the infants were approximately 3 months old by random assignment from an available pool. There were 33 males and 38 females assigned to groups containing infants of both sexes (heterosexual groups); 15 males and 15 females were assigned to groups containing only infants of the same sex (isosexual groups). The social behavior of subjects in each group was observed and recorded during six 50-day periods from 3 months of age to 3 1/2 years of age. Two sexually dimorphic patterns, mounting and presenting, were recorded for each subject as indices of protosexual (i.e., patterns eventually used in adult mating behavior) development. In addition, rough play, a dimorphic response that is not protosexual, was also recorded. Both males and females in the isosexual condition were characterized by a partial inversion of the manifestation of protosexual behavior. Isosexual males showed statistically less foot-clasp mounting and more presenting than heterosexual males. Conversely, isosexually reared females showed statistically more mounting and less presenting than heterosexual females. The effect of rearing animals in same-sex groups was greater on heterotypical than on homotypical protosexual behavior. Among isosexual males, presenting responses deviated from the heterosexual male standard to a greater extent than did mounting. Among isosexual females, mounting behavior deviated from the heterosexual female standard more than presenting. Results suggested that presenting behavior by males was more easily augmented by isosexual rearing conditions than was mounting by females. At no time during the experiments did isosexual females mount at frequencies or at group proportions that were indistinguishable from those of heterosexually reared males. In contrast, males reared isosexually showed average frequencies of presenting that equaled or exceeded means for females reared heterosexually. While mounting and presenting were both modified by same-sex rearing, rough-and-tumble-play frequencies were not influenced markedly in either sex. However, isosexual males did show statistically higher frequencies of rough play than heterosexual males during the final period of observation (3 to 3 1/2 years of age), and isosexual females showed less rough play than heterosexually reared females during the first year of life. Results support the conclusion that isosexual conditions can have a selective effect on the developmental expression of protosexual responses without altering the probability of display of other sexually dimorphic social behavior.(ABSTRACT TRUNCATED AT 400 WORDS)

Multiple ejaculations during prolonged sexual tests and lack of resultant serum testosterone increases in Male Stumptail Macaques (M. arctoides).

The sexual behavior of four male and four female adult stumptail macaques was observed in standardized 3-hr heterosexual pair tests. The males achieved from 11 to 19 ejaculations during a single test, thus apparently exceeding any other primate studied under laboratory conditions for the ability to display multiple ejaculatory patterns in relatively short periods of time. The stage of the menstrual cycle was not found to be related to the performance of the male or female, although this variable was not analyzed in depth. Progressive increases in the interejaculatory interval (IEI) occurred for all four males for the initial two to four ejaculations of the series, and then either a plateau or a transient decrease in this measure occurred. Since the data varied considerably for IEI as well as for other quantitative measures of sexual behavior for a given pair, individual data rather than group averages are presented. Blood samples drawn immediately before and after behavioral testing as well as at comparable intervals 1 week prior to behavioral testing were analyzed for testosterone concentration by radioimmunoassay for each male. Serum testosterone values were not found to be influenced by multiple ejaculations. Instead, decreased levels of serum testosterone were encountered on the second blood sample of the day for most males, regardless of whether sexual behavior occurred. The possibility that the decreases were related to stress effects of handling is discussed. Because of this complication, it could be only tentatively concluded that repeated copulation to ejaculation over a 3-hr period did not result in appreciable changes in testosterone levels.