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PubMed1997

Male sexual behavior is associated with LHRH neuron number in middle-aged rats.

LHRH administration is reported to facilitate male sexual behavior. The aim of the present study was to investigate whether male sexual behavior is associated with the number of LHRH neurons in the forebrain in middle-aged rats. Male Long-Evans rats (18-19 months) were assigned to three groups on the basis of sexual performance: (1) group MEI consisted of rats showing complete copulatory patterns, including mounts, intromissions and ejaculations, (2) group MI was composed of rats showing mounts and intromissions, but no ejaculation and (3) group NC were non-copulators, i.e. they did not show any copulatory behavior. Young adult rats (4-5 months), displaying sexual behavior, were used as controls. Following the sexual behavior tests, the number of LHRH neurons in the medial septum (MS), organum vasculosum of the lamina terminalis (OVLT), preoptic area (POA) and anterior hypothalamus (AH) was determined by immunocytochemistry. No difference was seen in the total number of LHRH neurons in these combined brain areas between group MIE and young controls. In the three middle-aged groups, the total number of LHRH neurons was greatest in group MIE, less in group MI, and lowest in group NC. In general, a similar trend was seen separately in the MS, OVLT and POA. These results suggest that changes in the number of LHRH neurons in the forebrain, in most cases, are age-related, at least in the middle-aged rats, but they also seem to be associated with male sexual performance.

Animals↗
PubMed1997

Behavioral regulation of gonadotropin-releasing hormone production.

In vertebrates reproductive readiness requires coordination between the sexes. Behavioral interactions with potential mates can initiate the neuroendocrine events that are required for successful copulation, ovulation, and fertilization. Regardless of the efferent pathway used, their targets are the neurons that produce and secrete gonadotropin-releasing hormone (GnRH). Several excellent animal models are currently under use to study the relationship between behavior and GnRH. In the musk shrew (Suncus murinus) starting 15 h after mating, prior to ovulation, GnRH-ir cell numbers are elevated along with GnRH content in brain and estradiol in plasma. Immunoreactive GnRH cell numbers also change in brains of female musk shrews sacrificed during, and directly after, brief interactions with males. These rapid changes in GnRH-ir cells are not correlated with measurable increases in GnRH content or elevations in plasma concentrations of estradiol. To determine which aspect(s) of the behavioral interaction is salient for the change in GnRH-ir, studies have been conducted in which interactions with males and their sensory cues were restricted during a 1-h interaction. In this study, behavioral interactions with an awake male behind a screen barrier resulted in a decrease in the numbers of GnRH-ir cells in the forebrain. Further studies with this animal model will help determine how behavioral inputs stimulate processing and release of GnRH.

Animals↗
PubMed2003

Sexual exhaustion in White New Zealand male rabbits of different ages.

Sexual exhaustion was studied in hybrid White New Zealand rabbits of different ages, for this purpose six young rabbits from 6 to 12 months of age, and six adult rabbits of 14-20 months of age were selected. Sexually receptive females were taken to the male's cage, for a period of 4 min, if copulation was not performed, the observation was then considered finished. If the male mounted within this period of time, the mounted female was immediately replaced by another female and 4 min of exposure time to the male were reinitiated, and repetitions were conducted until the male that was being studied refused to mount a new female at which time the male was considered to be sexually exhausted. Young rabbits mounted and ejaculated 9-10 times before sexual exhaustion. Adult rabbits showed a fluctuation of between 6 and 8 mounts per ejaculations before refusing another mount. The statistical analysis with a Mann-Whitney U-test, showed that the Rank sum for group A was 57, while for group B was 21. The U-value was 0.0 and the adjusted Z -2.9943. A significant difference was observed between groups with a value of P=0.00275. In the present study it was demonstrated that there is an influence of age on sexual behavior of rabbits.

Aging↗
PubMedDate not supplied

Sexual and transovarian transmission of Crimean-Congo haemorrhagic fever virus in Hyalomma truncatum ticks.

Male Hyalomma truncatum ticks were inoculated with Crimean-Congo haemorrhagic fever (CCHF) virus, hypostomectomized and then allowed to mate with uninfected females feeding on a naive rabbit. After mating, CCHF virus was reisolated from 2 out of 3 males tested and from 4 of 6 mated, engorged females (titre greater than or equal to 2.2 log LD50/ml). Vertical transmission was then demonstrated by virus reisolation from a portion of 2 of the 6 batches of eggs laid by the positive females. From these 2 positive egg batches, 6 larvae pools were tested with successful virus reisolation from one. Attempts to reisolate CCHF virus from 15 nymph pools of this positive batch of larvae were unsuccessful. Virus reisolation from gonopore-closed female H. truncatum which cofed with preinfected males demonstrated transmission in the absence of copulation. Rabbits that served as bloodmeal sources seroconverted after infestation by infected male ticks. However, CCHF virus was not reisolated from 3 gonopore-closed, engorged females, nor from their eggs, after feeding with hypostomectomized preinfected males. Transmission of CCHF virus during mating or cofeeding of adult H. truncatum, and subsequent transovarial transmission, appear to represent additional mechanisms of infection in the tick population, and may contribute to the maintenance of transmission in nature.

Africa, Western↗
PubMed1999

The partner preference paradigm: a method to study sexual motivation and performance of female rats.

Sexual behavior of the female rat consists of initiative, as well as receptive components. Previous studies on female sexual behavior have focused on the reflexive response to a male's mount, i.e., the lordosis reflex, whereas the initiative and soliciting gestures that are exhibited by the female during copulation were ignored by most researchers. This bias led to a misconception of the female's role in the sexual act, according to which the female is passive and submissive, whereas the male rat is sexually dominant or even aggressive. In this paper, we describe a procedure, the partner preference paradigm, designed to investigate and quantify sexual motivation, initiation and solicitation in female rats. In this paradigm, the female can control the sexual act because the mobility of her sexual partner is limited. This setting enables to measure a variety of soliciting behaviors that reflect the active seeking of sexual contact by an estrous female. In addition, this paradigm enables the evaluation of the females' motivation to engage in a sexual act, by measuring the preference for a sexually appropriate over an indifferent partner. Moreover, the partner preference paradigm may be easily adopted for studies in male subjects, allowing the comparison of males' and females' responses to various experimental conditions.

Animals↗
PubMed2006

Peptidomics analysis of neuropeptides involved in copulatory behavior of the mollusk Lymnaea stagnalis.

Male copulation behavior in mollusks is controlled by an array of peptide messengers. In the present study, we have used a peptidomics approach employing liquid chromatography in conjunction with electrospray mass spectrometry to characterize peptides contained in the penial complex of the freshwater snail, Lymnaea stagnalis. In addition to the previously described peptides, we have identified a group of novel peptides that share the carboxyl termini of -FVRIamide. A cDNA cloning study revealed the organization of the precursor, which contains 20 peptide domains with the carboxyl termini of -F(X)RIamide which are flanked by many putative proteolytic sites including the KR and the less commonly occurring (G)K and (G)R sites. In addition, there are several monobasic R and dibasic RR and KK sites that may be used for processing. We then used MALDI-TOF/TOF-MS in a data-dependent mode, which selected all the molecular ion species with the predicted masses of the mature -F(X)RIamide peptides, and performed MS/MS analysis on these peptides. This approach allowed us to identify all the predicted -F(X)RIamide peptides. Immunocytochemistry showed the localization of -FVRIamide immunoreactive neurons in several central ganglia, and immunoreactive axons in the penial complex. Finally, application of synthetic -FVRIamide peptides to an in vitro posterior vas deferens preparation showed inhibitory effect on the spontaneous contraction/relaxation cycle of the vas deferens.

Amino Acid Sequence↗
PubMed2001

Effects of age and experience on mating activity in the sibling species Drosophila pavani and Drosophila gaucha.

The effects of age and experience on sexual activity and on intra- and interspecific discrimination were studied in two sibling species of the mesophragmatica group, Drosophila pavani and Drosophila gaucha. Sexual activity of a total of 2970 individual couples of the same or of both species was observed at two ages: 10 days, ("young inexperienced") and 18-20 days ("old," either "inexperienced" or "experienced," if either the male or the female had copulated previously). In the 1186 (39.97%) pairs that mated, the latency to copula and duration of copula were registered. Age has a different effect in both species: "young" Drosophila pavani and "old" Drosophila gaucha females are less receptive to males of either species of the corresponding age. The receptivity of females is also reflected in heterospecific matings, as Drosophila gaucha males increase their mating activity with age. In both species, female receptivity decreases with experience, whereas mating activity of males increases with experience, especially that of Drosophila gaucha toward heterospecific females. Drosophila pavani females take longer to mate than those of Drosophila gaucha. In both species "old" males tend to mate faster, whereas experience increases the latency to mating in females and decreases it in males. Both species differ significantly in the duration of copula. It is longer in Drosophila pavani than in Drosophila gaucha and is determined mainly by the male. The duration of copula increases with age, especially in Drosophila pavani females, whereas it is reduced in males of the same species.

Aging↗
PubMed1991

A synthesized (biosocial) theory of rape.

Features of contemporary theories of rape are integrated with information on neurohormonal variables to formulate a synthesized theory of rape. It consists of four propositions: (a) Rape is motivated by two largely unlearned drives (a sex drive and a drive to possess and control). (b) Natural selection has favored men who more readily learn forced copulatory tactics than women and women who are more inclined than men to resist forced copulations. (c) The tendency to use forced copulatory tactics is largely a function of the strength of an individual's sex drive plus estimates of the probability of success minus the probability of being punished, divided by sensitivity to aversive stimuli. (d) Genes that have evolved primarily on the Y chromosome affect neurohormonal functioning in ways that alter the strength of the sex drive and sensitivity to aversive stimuli and thereby affect individual probabilities of committing rape.

Aggression↗
PubMed1992

Effects of unilateral hypothalamic manipulations on the sexual behaviors of rats.

Four experiments that assessed the contributions of each side of the hypothalamus to the control of sexual behavior found the following. (a) Exposing the left, but not the right, ventromedial nucleus to estrogen neonatally defeminized sexual behavior in female rats. This asymmetry did not reverse as sexual differentiation progressed. (b) Unilateral cuts lateral to the medial preoptic area disrupted mounting in females that had mounted regularly before surgery, when given testosterone. The deficits were greater when the cuts were on the left side, but a third of the females with unilateral cuts showed severe deficits regardless of the side. (c) Comparable cuts did not impair masculine sexual behavior in gonadally intact males. In fact, left-side cuts seemed to accelerate copulation in males. (d) Unilateral lesions of the ventromedial nucleus disrupted lordosis in female rats in an essentially all-or-none fashion. This effect did not vary with side.

Animals↗
PubMed1995

Opioids and sexual behavior of male rats: involvement of the medial preoptic area.

Local infusion of beta-endorphin (beta-END) into the medial preoptic area (MPOA) dose-dependently impaired the gating of the copulatory response and the execution of the sexual performance of sexually experienced, intact male rats. Local naloxone treatment prevented the impairment of the sexual response by beta-END, but failed to facilitate unimpaired copulation. Local infusion into the MPOA of equimolar doses of alpha-endorphin, dynorphin-A-(1-17) or met-enkephalin were less effective than beta-END. It is suggested that endogenous opioid systems in the MPOA are normally quiescent, and increased activity may be related to disrupted or inhibited male sexual behavior.

Animals↗
PubMed1995

Increased extracellular dopamine in the nucleus accumbens and striatum of the female rat during paced copulatory behavior.

Five groups of ovariectomized rats were tested during in vivo microdialysis, and concentrations of dopamine (DA) and its metabolites were determined in dialysate. In striatum, DA increased more in hormone-primed ovariectomized female rats pacing copulation than in those engaging in sex that could not pace, those that were hormone primed but tested without a male present, or oil-treated groups (p < .02). Administration of estrogen before microdialysis resulted in enhanced striatal DA in response to a male rat relative to the animals tested without a male (p < .06). Female rats that were pacing sexual behavior also exhibited a greater increase in accumbens DA than did the no-male, estrogen-primed, or oil-treated groups (p < .015). Nonpacing animals displayed a significant decrease in DA from accumbens 30 min after introduction of the male rat (p < .05) but otherwise were not different from pacing animals. Estrogen-treated animals also had an enhanced increase in accumbens DA compared with oil-treated rats (p < .05). These data suggest that DA release in the striatum and accumbens is dependent on the context in which sexual behavior occurs and that estrogen may in part modulate these dopaminergic responses.

Animals↗
PubMed2000

Dopamine release in the medial preoptic area of female rats in response to hormonal manipulation and sexual activity.

Dopamine (DA) is responsive to hormonal manipulations and has been implicated in the regulation of female rat sexual behavior. In the present studies, extracellular DA levels were assessed in the medial preoptic area (MPOA) of ovariectomized female rats in response to exogenous ovarian hormones and during sexual activity. In female rats primed with a low dose of estradiol benzoate (2 microg), but not with a higher dose (20 microg), a 500-microg progesterone injection increased extracellular DA and facilitated copulatory behavior. Extracellular DA levels in the MPOA were further augmented during sexual interactions with a male rat in a nonpacing copulatory chamber by either perineal or vaginal stimulation. However, in a pacing chamber, DA efflux did not increase, although the metabolites rose significantly during copulation. Together, these findings suggest that extracellular DA in the MPOA responds to the hormonal state of the female rat and may contribute to her expression of sexual behavior.

Animals↗
PubMed2000

Female presence during postejaculatory interval facilitates penile erection and 22-kHz vocalization in male rats.

During the postejaculatory interval (PEI), male rats exhibit prolonged immobility, 22-kHz vocalization, and penile erections. To test whether females modulate these behaviors, females were removed after the first or second ejaculation or left in the test chamber. Female presence during the PEI delayed exploratory behavior and facilitated vocalization and erection. Female stimulation of vocalization is consistent with the hypothesis that vocalization has a communicative function, not just a thermoregulatory one. The timing of the effect of females on erection suggests that males are sexually arousable well before they resume copulation. Therefore, erection may be better than vocalization as an indicator of the male's sexual refractoriness. The findings also challenge the conventional view that the PEI comprises absolute and relative sexual refractory periods marked, respectively, by the presence and absence of 22-kHz vocalization.

Animals↗
PubMed1983

Learned aversions to copulatory behaviors in male rats.

When male rats received an injection of lithium chloride immediately after an encounter with an estrous female, the vigor of subsequent copulatory responding was initially unaffected. After 5 to 10 such pairings, however, male rats displayed an aversion to copulatory behaviors; they ceased to copulate entirely. These aversions persisted when the rats were tested in a novel environment and extinguished after four nonreinforced trials. This multiple-trial adaptation of the conditioned taste aversion paradigm provides a new approach to the aversive control of sexual behavior.

Animals↗
PubMed1983

Gonadal hormone activation of male courtship ultrasonic vocalizations and male copulatory behavior in castrated male deer mice (Peromyscus maniculatus bairdi).

The influence of testosterone (T), a 5 alpha-reduced metabolite of T, dihydrotestosterone, and an aromatized metabolite of T, estradiol, on 35-kHz ultrasonic calling and male copulatory behavior by male deer mice (Peromyscus maniculatus bairdi) was examined. Daily treatment with testosterone propionate (TP), dihydrotestosterone propionate (DHTP), or estradiol benzoate (EB) restored male ultrasonic calling in long-term castrated males. Both TP and DHTP restored male copulatory behavior, but EB was ineffective in facilitating copulation. Synergism of EB and DHTP action was observed; when subthreshold doses of EB (1 microgram/day) and DHTP (50 micrograms/day) were administered in combination, male ultrasonic calling and male copulatory behavior were activated. In relation to other comparative findings, these results indicate that the degree to which male sexual behavior is facilitated by 5 alpha-reduced androgens and/or estrogens is influenced by the species and the particular pattern of masculine behavior under consideration.

Animals↗
PubMed1984

Hormonal modulation of genital reflexes in male and masculinized female dogs.

When testosterone propionate (TP) is administered to adult, neonatally castrated male dogs and to adult females with masculinized genitalia produced by prenatal and neonatal exposure to androgen, both types of animals are unsuccessful in their attempts to copulate with receptive females. They mount and thrust vigorously but do not achieve intromission and establish a copulatory "lock." The deficit could be due to incomplete "organization" of neuromuscular mechanisms mediating erection or to the fact that the penis of such dogs are abnormally short. In this experiment, neonatally castrated males and genitally masculinized females were tested before and after TP treatment for responses to manual stimulation of the genitalia. An additional experimental group consisted of males castrated as adults, and there was a control group of normal males. After a series of TP injections, neonatally castrated males, adult castrates, and genitally masculinized females exhibited complete and strong erectile and ejaculatory reflexes. Erect penis lengths of neonatally castrated males and masculinized females were significantly shorter than those of normal males or of males castrated as adults. It is tentatively concluded that the failure of males castrated at birth, and of genitally masculinized females, to insert and lock when mounting receptive females is due to incomplete penile development and not to incomplete "organization" of spinal reflex mechanisms. However, because artificial stimulation was employed, results of this study do not prove that central nervous system mechanisms necessary for insertion and locking in copula were normally developed.

Androgens↗
PubMed1989

Sexual-discrimination learning in male Japanese quail (Coturnix coturnix japonica).

We investigated how male Japanese quail (Coturnix coturnix japonica) learn through extensive social and sexual experience to discriminate between male and female conspecifics. Opportunity for heterosexual copulation was important for this learning, but even extensive copulatory opportunity was not sufficient to produce a sexual discrimination; subjects also required exposure to other males. Exposure to females after copulatory opportunity did not produce a sexual discrimination but facilitated its acquisition. Time or exposure to only the visual features of male birds (provided by taxidermic models) after copulatory opportunity did not result in differential responding to male and female conspecifics. Finally, presenting stimulus birds one at a time proved to be a more sensitive test of sexual-discrimination learning than presenting two stimulus birds at the same time. The results indicate that sexual-discrimination learning is similar to conventional associative learning.

Animals↗
PubMed1990

Effects of male pre-ejaculatory vocalizations on female receptive behavior in the rat (Rattus norvegicus).

Both male and female rats (Rattus norvegicus) emit ultrasounds during copulation. Bursts of ultrasounds from males that occur as ejaculation approaches are lower in frequency, longer in duration, and louder than those that appear earlier in the ejaculatory series. We attempted to determine if these pre-ejaculatory calls affect female sexual behavior. The behavior of females paired with devocalized males was compared with that of females paired with intact males, and in a second experiment tape-recorded vocalizations were played to females paired with devocalized males. Females were less receptive when paired with devocalized males; they were less likely to remain stationary when males attempted to mount. Playback of both types of calls restored female immobility toward control levels, although pre-ejaculatory calls were more effective than mating ones. Pre-ejaculatory calls restored running and training levels somewhat toward control level but to a lesser extent than female immobility.

Animals↗