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PubMed1982

Ovulatory function after tubal microsurgical procedures in the rabbit.

Ovulatory function as correlated with the production of corpora lutea was studied in 72 rabbits that were subjected to unilateral tubal microsurgical procedures. Isthmo-isthmic reanastomosis was performed in 11 rabbits, ampullo-isthmic reanastomosis in 10, and ampullo-ampullary reanastomosis in 11. In a second group of 40 animals, 20% to 100% of the isthmic portion (n=20) and 20% to 60% of the ampullary portion (n=20) were resected with reanastomosis. After natural copulation of the animals, without administration of gonadotropin, the numbers of corpora lutea on the operated and control side were counted. A slight but nonsignificant overall reduction in corpora lutea on the anastomosed side was observed. This showed no correlation to amount of tubal resection or proximity of the anastomosis to the ovary.

Animals↗
PubMed1983

Surgical alteration of the mesosalpinx and its influence upon ovarian ovulatory function in the rabbit.

Ovarian ovulatory function as correlated with the production of corpora lutea was studied in 58 rabbits that were subjected to unilateral surgical procedures. Initially, a resection of 50% of the isthmus and 50% (n = 8) or all (n = 8) of the corresponding mesosalpinx was performed. Next, 50% of the ampulla and 50% (n = 7) or all (n = 8) of the corresponding mesosalpinx was resected. Finally, a variable length, either one third, two thirds, or all, of the ampulla (n = 27) was dissected from the adjacent mesosalpinx. After natural copulation of the animals, without administration of gonadotropin, the numbers of corpora lutea on the operated and control sides were counted. A slight but nonsignificant overall reduction in corpora lutea on the operated side was observed. This showed no correlation either to the amount of mesosalpinx resected or the proximity of the surgical procedure to the ovary. Also, no correlation was observed with the length of dissected ampullary part.

Adnexa Uteri↗
PubMed1975

Effects of testosterone on the behaviour of the domestic chick. I. Effects present in males but not in females.

In male chicks, specific facilitation of male copulatory movements occurs at a lower dosage of testosterone oenanthate than does facilitation of approach to the test object, or of attack. The latter effects can be dissociated in other ways from the first; they may depend upon a single central change in visual responsiveness or persistence. Females show none of these changes, although they are capable of the behaviour patterns involved, and do show other behavioural effects of testosterone. On day 3 normal males copulate and attack more, and flee less than do females.

Age Factors↗
PubMed1978

Acute changes in plasma testosterone levels and their relation to measures of sexual behaviour in the male house mouse (Mus musculus).

There is an increasing amount of evidence, from several mammalian species, that plasma testosterone levels increase acutely when the male is exposed to sexual stimuli. Work reported here investigates whether such responses occur in male mice, and whether their incidence is related to measures of sexual behaviour. Close proximity of oestrous female mice was found to result in increased plasma testosterone levels in some strains within 15 min. Immediately after a sexual behaviour test, plasma testosterone levels were higher in males showing sexual responses. There were correlations between testosterone levels and mount latency, but none with ejaculation latency. Testosterone levels were greatest at the initiation of mounting responses, and declined during copulation, although not significantly.

Animals↗
PubMed1986

Anteromedial hypothalamic lesions block proceptivity but not receptivity in the female common marmoset (Callithrix jacchus).

The sexual behavior of 8, estradiol-treated, ovariectomized common marmosets was recorded prior to and after bilateral radiofrequency lesions of the hypothalamus. Lesions of the anterior hypothalamus, which extended to varying degrees into the medial hypothalamus, virtually abolished proceptive tongue-flicking and staring displays. Tongue-flicking during copulation also decreased, but the females did not show any significant increase in the number of mounts which they refused or terminated with the exception of one animal which had received more extensive damage to the medial hypothalamus. Significant increases in the frequencies of allogrooming and grooming invitations also occurred after the females had been lesioned. Sexual behavior was not significantly altered in 3 females which received sham lesions. These results provide the first direct evidence for a neuroanatomical distinction between hypothalamic mechanisms which regulate proceptivity and receptivity in primates.

Animals↗
PubMed1988

Neuron activity of the ventromedial hypothalamus and the medial preoptic area of the female monkey during sexual behavior.

To elucidate the neural mechanisms of the sexual behavior of the female monkey, single neuron activity of the ventromedial hypothalamus (VMH) and the medial preoptic area (MPOA) was recorded during sexual behavior with a male partner. Copulation was initiated when either the male's touch elicited passive presenting ('receptive presenting') or when the female's active presenting ('proceptive presenting') evoked mounting from the male. Proceptive presenting with no mating acts evoked activity changes in about 40% of cells in the VMH (mainly excitation) and MPOA (mainly inhibition). When the male's mating acts were manifested, 56% of VMH cells and 87% of MPOA cells showed firing changes during presenting, with the proportion of MPOA cells which showed excitation significantly increased. Progress of mating acts of the male partner (e.g. increases in the rate and/or number of thrusting), enhanced activity changes in about 40% of VMH and 70% of MPOA cells tested. The findings suggest that VMH and MPOA cells are involved in the control of sexual behavior in different ways: excitation of the VMH and inhibition of MPOA are related to execution of presenting, while excitation of MPOA is related to sexual intercourse with a male partner; and mating acts of a male partner modulate activity of both VMH and MPOA neurons of the female.

Animals↗
PubMed1990

Correlation of dopamine release in the nucleus accumbens with masculine sexual behavior in rats.

Extracellular dopamine (DA) and 3,4-dihydroxyphenylacetic acid (DOPAC) in the nucleus accumbens (N. Acc.) were measured by in vivo microdialysis during male sexual activity. DA and DOPAC were significantly increased during copulation, but not during mild tail pinch. These results are consistent with studies showing increases in N. Acc. DA associated with positively reinforcing environmental stimuli.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1993

Sexual stimulation activates c-fos within estrogen-concentrating regions of the female rat forebrain.

Regions of the brain that concentrate estrogen and progesterone are thought to regulate female sexual behavior by altering gene expression and neural sensitivity to afferent stimulation. We used immunocytochemistry and in situ hybridization to examine c-fos gene expression within estrogen-concentrating regions of the forebrain following various types of sexual stimulation with or without hormone treatment. Ovariectomized rats received injections of estradiol benzoate 48 h and progesterone 4 h before testing. Control rats that had been ovariectomized at least 5 months before testing did not receive hormone treatment. Rats were then either placed into bilevel testing chambers with sexually vigorous males, received manual stimulation of the flanks, received vaginocervical stimulation with a glass rod, or were left in their home cages. Copulation with intromission and ejaculation in hormone-treated rats, or stimulation of the vaginal cervix in both hormone-treated and control rats, produced a dramatic induction of c-fos mRNA and Fos-like immunoreactivity in estrogen-concentrating regions, such as the lateral septum, medial preoptic area, bed nucleus of the stria terminalis, paraventricular nucleus of the hypothalamus, ventromedial hypothalamus, lateral habenula, and medial amygdala, in addition to regions that do not readily concentrate estrogen, such as the neocortex, thalamus, and striatum. Mechanical stimulation of the flanks produced a smaller induction of Fos in these rats, whereas hormone treatment alone had no effect. These data demonstrate that afferent sensory stimulation, but not estrogen or progesterone, regulates c-fos gene expression within different estrogen-concentrating and non-concentrating regions of the female rat forebrain.

Animals↗
PubMed1994

Estradiol and progesterone influence the response of ventromedial hypothalamic neurons to tactile stimuli associated with female reproduction.

Stimulation of the vagina and cervix, provided by the male during copulation or manually with a probe, causes many behavioral and endocrine changes associated with female reproduction in rats. Previously, we found that vaginal-cervical stimulation (VCS), by mating or manual probing, increases the expression of Fos-immunoreactivity (Fos-IR) in discrete populations of neurons in the preoptic area, mediobasal hypothalamus and midbrain, suggesting that these neurons respond to VCS. The purpose of the present study was to determine if hormonal priming would increase the number of Fos-IR cells following VCS. Contrary to our hypothesis, in Experiment 1 priming animals with a behaviorally effective dose of 17 beta-estradiol benzoate followed 48 h later by progesterone caused a trend towards a decrease in the number of VCS-induced Fos-IR cells in the ventromedial hypothalamus. In Experiment 2, which was done to confirm this decrease in VCS-induced Fos-IR neurons by hormones, this effect was found to be statistically significant. Furthermore, this hormone-induced decrease in VCS-responsive cells was localized to the ventromedial nucleus of the hypothalamus, an area rich in estrogen and progestin receptors. No effects of hormone treatment on VCS-induced Fos-IR were observed in any other brain regions analyzed. These findings suggest that steroid hormones may elicit some of their effects on female reproductive behavior and physiology by altering the responsiveness of ventromedial nucleus neurons to vaginal-cervical stimulation.

Animals↗
PubMed1994

Endogenous opioids and sexual motivation and performance during the light phase of the diurnal cycle.

The sexual motivation and performance of sexually experienced male rats were tested during the light phase of the diurnal cycle after treatment with saline or 1 mg.kg-1 naloxone in a bilevel testing box. The sexual motivation during the light phase, as assessed by the increase in anticipatory level changes prior to introduction of a receptive female on subsequent weekly sessions, was comparable to that during the dark phase. Opioid blockade reduced the increase of level changes, suggesting that endogenous opioids are involved in sexual motivation. The sexual performance was impaired during the light phase. Naloxone treatment failed to affect the sexual performance, other than that the post ejaculatory refractory period was increased. This increased latency to re-initiate copulation may be an expression of the reduced sexual motivation. It is concluded that endogenous opioids are not involved in the regulation of the impaired sexual performance during the light phase of the diurnal cycle. In contrast, the sexual motivation, which displays no marked diurnal variation, may be stimulated by endogenous opioids.

Animals↗
PubMed1994

The medial preoptic area is involved in both sexual arousal and performance in male rats: re-evaluation of neuron activity in freely moving animals.

A total of 74 single unit activities was recorded from the medial preoptic-anterior hypothalamic continuum (MPOA) during free copulatory behavior of male rats. Forty-six units (62.2%) showed changed activities during at least one phase of male copulatory movements; 26 units (35.1%) increased in the firing rate during pelvic thrusting; 32 units (43.2%) increased in activity during backward jumping immediately after intromission; only one unit (1.4%) showed decreased firing rate during thrusting and backward jumping; 12 units (16.2%) increased in activity during pursuit of a female; 19 units (25.7%) were suppressed during genital grooming. Furthermore, 67 units (90.5%) showed a significant change in activity throughout a series of copulatory behavior. From the introduction of a female up to ejaculation, relatively large number of units increased in the firing rate above the value during pre-introduction adaptation period. During postejaculatory interval, however, most units decreased in activity below the level during copulation. These results strongly suggest that the MPOA is involved in both sexual arousal and performance in male rats.

Animals↗
PubMed1995

Lesions of the medial prefrontal cortex and sexual behavior in the male rat.

Lesions of the cerebral cortex near the midline in the frontal region appearing to destroy most of the cingulate cortex and adjacent prefrontal areas had profound effects on male rat sexual behavior. At the first postoperative tests, one week after the lesion, the mount and intromission latencies were extremely long (> 60 min). They continued elevated at every fortnightly test until postlesion week 13, when they were no longer different from controls. However, the proportion of animals that intromitted or ejaculated was reduced at this time. The lesion had a slight effect on the number of intromissions and on the intromission ratio, but did not reliably modify other parameters of sexual behavior in those males that copulated after operation. These data suggest that the medial prefrontal cortex is important for the initiation of sexual behaviour but less so for its execution. It is proposed that the elaboration and/or interpretation of environmental stimuli are rendered deficient by the lesion. Consequently, sexual behavior is activated only with difficulty. This coincides with the arousal hypothesis proposed by Beach [8]. There appears to exist a spontaneous recovery of the mechanisms responsible for the activation of sex behavior because the lesioned group was not different from the sham or intact groups 13 weeks postlesion. Remaining cortical tissue or other brain structures may compensate for the initial deficiencies. However, the lesion's effect on intromission behavior did not diminish with time. This could suggest that possible motor deficiencies produced by the lesion are irreversible.

Animals↗
PubMed1983

The initiation of spermiogenesis in the nematode Caenorhabditis elegans.

Spermiogenesis in nematodes involves the activation of sessile spherical spermatids to motile bipolar amoeboid spermatozoa. In Caenorhabditis elegans males spermiogenesis is normally induced by copulation. Spermatids transferred to hermaphrodites as well as some of those left behind in the male become spermatozoa a few minutes after mating. Spermiogenesis can also be induced in vitro by the ionophore monensin (G.A. Nelson and S. Ward, 1980, Cell 19, 457-464) and by weak bases such as triethanolamine. Both triethanolamine and monensin cause a rapid increase in intracellular pH from 7.1 to 7.5 or 8.0. This pH increase precedes the subsequent morphological events of spermiogenesis. Triethanolamine or monensin must be present throughout spermiogenesis for all cells to form pseudopods, but once pseudopods are formed the inducers are unnecessary for subsequent motility. The pH induced spermiogenesis is inhibited by drugs that block mitochondria or glycolysis. Protease treatment can also induce spermiogenesis without increasing intracellular pH, apparently bypassing the pH-dependent steps in activation and the requirement for glycolysis. These results show that the initiation of spermiogenesis in C. elegans, like some steps in egg activation and the initiation of sea urchin sperm motility, can be induced by an increase in intracellular pH, but this pH change can be bypassed by proteolysis.

Animals↗
PubMed1995

Induction of mating behavior by apomorphine in sexually sated rats.

We have tested the hypothesis, suggested by our previous neurochemical studies, that the inhibition of sexual behavior that follows unrestricted mating could be caused by a blockade of dopaminergic transmission. Male rats were allowed to copulate until they reached a satiety criterion. The following day, after verification that they were sexually inactive, the animals were injected with the dopamine agonist, apomorphine, at doses of 80, 200, and 500 micrograms/kg body weight and their behavior with receptive females was recorded. A bell-shaped dose-response curve was found, with the 200 micrograms/kg dose having the maximal stimulatory effects on mating. Whereas these findings seem to support the above hypothesis, it should be noted that apomorphine treatments were unable to restore fully the copulatory pattern shown by sexually rested animals. This could be due to several factors including the interference of apomorphine-induced stereotypies, and/or the involvement of additional transmitter systems in the mechanisms of sexual satiety.

Animals↗
PubMed1985

Schistosoma mansoni, S. japonicum, and S. haematobium: permeability to acidic amino acids and effect of separated and unseparated adults.

Permeability of the tegument of male and female Schistosoma mansoni was measured in vitro and a comparison was made between copulating and separated worms. In unpaired (separated) schistosomes, a carrier-mediated (selective) transport system for acidic amino acids was demonstrated. Males and females exhibited similar uptake rates for aspartate and glutamate. Half-saturation constants for aspartate (males, 0.035 +/- 0.008 mM; females, 0.026 +/- 0.006 mM) and glutamate (males, 0.010 +/- 0.007 mM; females, 0.015 +/- 0.004 mM) were determined for separated worms only. Time-course studies provided estimates of aspartate influx rates in males (7.3 pmol min-1 worm-1) and females (2.3 pmol min-1 worm-1). The most dramatic observation, however, was that, in copula, neither male nor female schistosomes took up acidic amino acids, but may have excluded these compounds. Thus, this ouabain-insensitive, mediated mechanism was operational only when the worms were unmated. In S. japonicum, no uptake of glutamate was observed in either mated or separated males and females. In S. haematobium, saturable uptake of aspartate was apparent in both mated and unmated males and females, indicating that species-specific differences in uptake of acidic amino acids existed. These studies indicate the need for cautious interpretation of data obtained from in vitro analyses of separated male and female mansonian schistosomes, and that such conditions may not reflect in vivo or in copula function.

Animals↗
PubMed1990

Circulating estradiol and the activation of male and female copulatory behavior in Japanese quail (Coturnix japonica).

Previous experiments using systemic and preoptic area (POA) hormone treatments have shown that aromatization of testosterone (T) to estrogen (E) is essential for activation of male-typical copulatory behavior in castrated male Japanese quail (Coturnix japonica). Two experiments were conducted to determine whether circulating estrogen levels characteristic of normal intact males are high enough to activate male-typical or female-typical copulatory behavior. In Experiment 1, blood samples were drawn every 4 hr from groups of sexually active male quail housed under a 16L:8D light-dark cycle, and assayed for estradiol (E2) concentration. The mean +/- SEM serum E2 was 54.2 +/- 3.6 pg/ml, and no daily cycle in serum E2 was seen. The males were then tested for sexual behavior; 88% mounted females, and 23% crouched when mounted by males. In Experiment 2, 51 males were castrated and implanted with Silastic tubes containing estradiol benzoate (EB) and/or cholesterol designed to produce five different levels of serum E2, then tested for male- and female-typical copulatory behavior and bled. The serum E2 in EB-implanted quail which mounted (253 +/- 30 pg/ml) was significantly higher than that of intact quail in Experiment 1, and only 10.2% of intact males had serum E2 as high as the minimum associated with mounting in EB-implanted males. These results show that serum E2 levels in intact males are not high enough to support male-typical copulation, and that aromatization in the POA to produce locally high E2 levels may be required. In addition, it was found that the threshold serum E2 to elevate receptivity significantly was 3.6 times the intact male level, and only slightly higher than serum E2 reported for intact females. Thus the lack of receptivity in intact males is probably due to insufficient circulating E2, and the male is not defeminized with respect to sensitivity to E2 for activation of receptivity.

Animals↗
PubMed1978

Effects of ovariectomy and estradiol replacement therapy upon the sexual and aggressive behavior of the greater galago (Galago crassicaudatus crassicaudatus).

The effects of ovariectomy and estradiol treatment upon sexual and aggressive behavior were studied in a prosimian primate, the greater galago. Ovariectomized galagos were sexually unreceptive and frequently aggressive, but retained their sexual attractiveness to males. When females were treated with estradiol monobenzoate, however, their aggression and refusals of males' mounting attempts decreased markedly. Although males mounted these females, they usually failed to copulate, possibly because the females did not perform certain postural adjustments which assist males to intromit. Estradiol benzoate alone, even in large does, does not fully restore patterns of mating behavior in ovariectomized female greater galagos. These observations on a prosimian primate are in striking contrast to the results of similar work on Old World monkeys and chimpanzees.

Aggression↗
PubMed1983

Female sexual behavior displayed by androgenized female rhesus macaques.

Adult, prenatally androgenized female rhesus macaques (female pseudohermaphrodites) that had been ovariectomized were treated with estradiol benzoate (20 micrograms/day) and paired with males at weekly intervals for 4 weeks beginning on Day 12 of injection. Their sexual behavior was compared to that of a control group of females. The sexual behavior of the males toward the two groups of genetic females (control females with normal female genitalia and hermaphrodites with well-formed male genitalia) was also observed. Females and hermaphrodites were equally receptive to male invitations to copulate. Although there were some differences in the specific components of proceptive behavior displayed by the two groups, the overall differences were negligible. Earlier studies had shown that infant and juvenile hermaphrodites resemble males in patterns of play and sexual behavior. When treated with testosterone as adults and paired with receptive females, they displayed mounting patterns typical of males--one of seven hermaphrodites achieved intromission and ejaculated. It has now been demonstrated that when treated with estrogen and paired with males, they responded as females. Hence, the capacity to behave sexually as males is not incompatible with the capacity to respond sexually as females under certain hormonal and environmental conditions.

Aggression↗