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PubMed2000

Mate choice in Drosophila melanogaster and D. sechellia: criteria and their variation depending on courtship song.

Courtship song is one of the most important male signals in Drosophila mating. A female D. melanogaster copulates more readily when given a conspecific type of courtship song. Female D. melanogaster accepted winged D. sechellia more than wingless ones in a no choice test. Copulation frequencies varied between strains and were significantly correlated with male mating propensity of D. sechellia. Females from three of five strains of D. sechellia accepted winged D. melanogaster less than wingless ones in no choice tests, suggesting that D. melanogaster songs reduce mating in D. sechellia females. Multiple choice tests showed that males prefer conspecifics. In female choice tests, D. melanogaster females copulated with winged heterospecific D. sechellia males more than with wingless conspecific D. melanogaster males in the confined condition, suggesting that song differences between D. melanogaster and D. sechellia affect D. melanogaster females less than the absence of courtship song. Copyright 2000 The Association for the Study of Animal Behaviour.

Journal Article↗
PubMed2001

Incipient sexual isolation in the nasuta-albomicans complex of Drosophila: no-choice experiments.

Drosophila nasuta nasuta and Drosophila nasuta albomicans are cross-fertile races of Drosophila. Hybridization between these races in the laboratory has given rise to new races (Cytoraces), among which karyotypic composition differs from one another and also from those of the parental races. In this study, we search for the evidence of incipient reproductive isolation among the parental races and four Cytoraces by assessing the fraction of no-matings, mating latency and copulation duration in all possible types of homo- and heterogamic crosses (N = 4184). In no-choice conditions, the latency time (time to initiation of copulation) is lower in homogamic crosses than in heterogamic crosses for both parental races and Cytoraces. Latency time and copulation duration are negatively correlated, whereas fraction of no matings is positively correlated with latency time. Thus these six closely related races of the nasuta-albomicans complex show the initiation of the earliest stages of pre-zygotic isolation, manifested as a tendency for matings to be initiated earlier and more often, and for a longer duration, among homogamic rather than heterogamic individuals

Animals↗
PubMed1981

Prostaglandins, clonidine and sexual receptivity in the guinea pig.

Prostaglandins E1 and F2 alpha suppressed lordosis in ovariectomized guinea pigs brought into estrus with estradiol benzoate and progesterone. Pretreatment with clonidine prevented this action of the prostaglandins, but if the animals were first given prostaglandin and allowed to go out of estrus, then clonidine did not restore lordosis. In a previous study it was found that the abbreviation of estrus induced by copulation was also blocked by clonidine, again only if it were given before the inhibitory treatment. These results suggest tht prostaglandin, perhaps released from the female reproductive tract, could mediate the inhibitory effect of copulation, and radioimmunoassays of prostaglandin F2 alpha and its principal metabolite PGFM revealed substantial elevations in the concentrations of these materials in trunk blood after copulation. We discuss the possibility that prostaglandins may suppress sexual receptivity by interfering with an alpha-adrenergic mechanism.

Animals↗
PubMed1986

Dopaminergic control of male sex behavior in rats: effects of an intracerebrally-infused agonist.

Systemically-administered dopaminergic drugs have been found to facilitate sexual behavior of men and male rats. The present experiments investigated the localization within the brain of dopaminergic effects on copulation of male rats. Apomorphine, a dopamine agonist, was microinfused into the medial preoptic area, caudate-putamen, nucleus accumbens, lateral septum and lateral ventricle. The lowest dose of apomorphine (0.2 microgram) infused into the ventricle reduced the number of ejaculations, slowed the rate of intromitting and decreased the percentage of mounts on which the male gained vaginal intromission. The higher two doses (0.5 and 2.0 micrograms) infused into the medial preoptic area and, in some cases, the ventricle, increased the number of ejaculations and the percentage of mounts with vaginal intromission, increased the rate of intromitting and decreased the latency to ejaculate and the postejaculatory interval before resuming copulation. Infusions into the caudate-putamen and lateral septum were without effect. Those into nucleus accumbens produced only a slight dose-related decrease in latency to begin copulating. The copulatory impairments associated with infusions of the lowest dose into the ventricle may have resulted from stimulation of autoreceptors, or from preferential stimulation by low doses of an undetermined area. The facilitative effects of the two higher doses into the medial preoptic area and lateral ventricle may have been due to stimulation of dopaminergic postsynaptic receptors.

Animals↗
PubMed1995

Dopamine release in the nucleus accumbens during sexual behavior in prenatally stressed adult male rats.

In vivo microdialysis experiments were performed on the nucleus accumbens (NAc) during observation of sexual behavior (including motivation and copulation) to determine if there were any changes in NAc dopamine (DA) transmission in prenatally stressed (PS) adult male rats. Approximate 37% of control males and 83% of PS males did not exhibit copulation during the sexual behavior tests and no significant changes in NAc DA release were seen during exposure to estrous females. In contrast, both control and PS males that displayed copulatory behavior showed a marked increase in NAc DA release when presented with a sexually receptive female behind a screen and this increased further during actual copulation. The increase in DA release in copulatory PS males was not significantly different from that in sexually active control males. In addition, a similar extent in DA release induced by high potassium perfusate was observed in all rats. These results suggest that prenatal stress may result in a deficit in DA neurotransmission in the NAc and this deficit may possibly cause impaired male sexual behavior in rats.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1995

Co-localized neuropeptides conopressin and ALA-PRO-GLY-TRP-NH2 have antagonistic effects on the vas deferens of Lymnaea.

We examined functional aspects of co-localization of neuropeptides involved in the regulation of male copulation behaviour in the simultaneous hermaphrodite snail Lymnaea stagnalis. The copulation behaviour is controlled by several types of peptidergic neurons that include a cluster of neurons in the anterior lobe of the right cerebral ganglion. All anterior lobe neurons express the gene encoding Ala-Pro-Gly-Trp-NH2 (APGWamide), and a subset of neurons also express the vasopressin-related conopressin gene. Immunocytochemical and peptide chemical experiments show that both APGWamide and conopressin are transported to the penis complex and the vas deferens via the penis nerve. Co-localization of the two peptides was also observed in some, but not all, axon bundles that run along the vas deferens. APGWamide and conopressin were structurally identified from the penis complex with vas deferens. Conopressin excites the vas deferens in vitro, whereas APGWamide inhibits the excitatory effects of conopressin, both in a dose-dependent fashion. We propose that the antagonistic effects of these peptides on the vas deferens underlie its peristalsis. Thus, these peptides play an important role in the control of ejaculation of semen during copulation.

Amino Acid Sequence↗
PubMed1984

Individual analysis of age-associated changes in reproductive activity and lifespan of Drosophila virilis.

In the TK strain of Drosophila virilis, age-associated changes in reproductive activities (copulating activity and fertility in males and egg-laying activity in females) and lifespan were examined in individual flies. The mean lifespan of individually aged flies was about 11 weeks for both males and females. Copulating activity was maximum in two-week old males, then decreased gradually and finally ended at the age of 13 weeks at which about half of males were still surviving. Females also had a peak in egg-laying activity at the age of two weeks while no eggs were laid by females older than ten weeks, although more than half of females were alive at the stage. Analyses of the relationship between reproductive activity and lifespan of individual flies revealed that shorter lived males exhibited a higher copulating activity in the early stage of their lives than longer lived males. In males whose lifespan was less than ten weeks the reproductive period increased with the lifespan while the post-reproductive period was almost constant (one to two weeks). In males living longer than ten weeks, the reproductive period remained constant (about eight weeks) while the post-reproductive period increased in parallel with the total lifespan. Similar tendencies were also observed in the egg-laying activity of female flies.

Aging↗
PubMed2005

Fertility assurance and breeding synchrony.

Extrapair fertilizations are an important factor in reproduction of many bird species. It has been suggested that pursuit of extrapair fertilizations provides a selective pressure capable of affecting the "ecological" attributes of some bird species. It is known that in some cases the pursuit of extrapair copulations is motivated by fertility assurance. That is, there are populations in which (i) some males and females cannot produce viable offspring, and (ii) there is no pre-copulatory way to choose a compatible mate. In such situations individuals mate for "economic" reasons and attempt to secure reproduction by copulating with multiple partners. Here we formulate and analyze a simple game theoretical model addressing the interplay between environmental constraints and the pursuit of fertility assurance via extrapair copulations in determining breeding synchrony. Our results indicate that breeding synchrony in such cases is determined by the magnitude of the costs (due to environmental constraints) of breeding asynchronously versus the worth of the attendant increase in extrapair opportunities.

Animals↗
PubMed2005

Cost of reproduction in Callosobruchus maculatus: effects of mating on male longevity and the effect of male mating status on female longevity.

One of the most studied life-history trade-offs is that resulting from the cost of reproduction: a trade-off arises when reproduction diverts limited resources from other life-history traits. We examine the cost of reproduction in male, and the effect of male mating status on female Callosobruchus maculatus seed beetles. Cost of reproduction for male C. maculatus was manifested as reduced longevity. There was also a positive relationship between male body size and male longevity. Females mated to males that had already copulated twice did not live as long as females mated to males that had copulated once or not at all. The third copulation of males also lasted longer than the two previous ones. We conclude that even though the cost of reproduction for males has been studied much less than that in females, there is growing evidence that male reproductive effort is more complex than has traditionally been thought.

Analysis of Variance↗
PubMed2004

The role of oxytocin and the paraventricular nucleus in the sexual behaviour of male mammals.

The paraventricular nucleus of the hypothalamus contains the cell bodies of a group of oxytocinergic neurons projecting to extrahypothalamic brain areas and to the spinal cord, which are involved in the control of erectile function and copulation. In male rats, these neurons can be activated by dopamine, excitatory amino acids, nitric oxide (NO), hexarelin analogue peptides and oxytocin itself to induce penile erection and facilitate copulation, while their inhibition by gamma-aminobutyric acid (GABA) and GABA agonists and by opioid peptides and opiate-like drugs inhibits sexual responses. The activation of paraventricular oxytocinergic neurons by dopamine, oxytocin, excitatory amino acids and hexarelin analogue peptides is apparently mediated by the activation of nitric oxide (NO) synthase. NO in turn activates, by a mechanism that is as yet unidentified, the release of oxytocin from oxytocinergic neurons in extrahypothalamic brain areas. Paraventricular oxytocinergic neurons and mechanisms similar to those reported above are also involved in the expression of penile erection in physiological contexts, namely, when penile erection is induced in the male by the presence of an inaccessible receptive female, which is considered a model for psychogenic impotence in man, as well as during copulation. These findings show that paraventricular oxytocinergic neurons projecting to extrahypothalamic brain areas and to the spinal cord and the paraventricular nucleus play an important role in the control of erectile function and male sexual behaviour in mammals.

Animals↗
PubMed2005

Hormonal responses to different sexually related conditions in male rats.

Plasma levels of corticosterone (C) and testosterone (T) increase after sexual activity in males of several species. However, the physiological significance of these increases has not been elucidated. In the present study, hormonal response to different conditions linked to sexual activity was assessed. In the first experiment, plasma levels of C and T were assessed both in sexually experienced and naive male rats after the following conditions: (A) control group, without sexual stimulation; (B) males exposed to ovariectomized females; (C) males exposed to intact, non-receptive females; (D) males exposed to receptive females with the vagina obstructed, to avoid intromission; (E) males exposed to receptive females: but separated by a grid that prevents physical contact; (F) males exposed to receptive females during 30 min. In a second experiment, experienced male rats were allowed to repeatedly copulate until reaching the criteria for sexual exhaustion, and 24 h later, they were allowed to copulate. Once sexually related conditions ended, males were killed and their blood was obtained. C and T plasma levels were assessed by HPLC with ultraviolet (UV) detection. Results indicate that T did not increase significantly in naive male in any sexual condition, while in the experienced males, significant increases were observed with the mere presence of a receptive female and also after ejaculation. These increases were significantly larger in experienced males. On the other hand, C also increased in all sexual conditions, both in experienced and naive rats; however, the increase observed was larger in experienced males. Regarding sexual satiety, both C and T increased after copulating ad libitum to satiety. T increased almost three-fold compared to control, while C increased two-fold. No significant changes were observed in either one of the steroids 24 h after sexual exhaustion, even though males remained with a receptive female during an hour. These results show that sexual experience has an important influence on the hormonal response to sexual activity. C rises could be directly related to sexual arousal involved in the different sexual conditions, while T rises seem to have a direct relationship with both the motivation and execution aspects of masculine sexual behavior.

Animals↗
PubMed2003

Permanent changes in sexual behavior induced by medial preoptic area kindling-like stimulation.

Kindling is a model of neuronal plasticity in which repeated electrical stimulation of certain brain areas leads to the progressive development of motor seizures. We have previously shown that medial preoptic area (MPOA) kindling induces sexual behavior in non-copulating male rats. In the present experiment, we found that previously non-copulating male rats display sexual behavior even 8 months after kindling stimulation had ceased. In addition, elicitation of an afterdischarge (AD) or stimulation until an intermediate stage was sufficient to induce sexual behavior in previously non-copulating male rats. These results suggest that kindling like stimulation, without seizure development, can induce permanent behavioral changes.

Animals↗
PubMed1997

Behavioral interactions have rapid effects on immunoreactivity of prohormone and gonadotropin-releasing hormone peptide.

The nervous system responds to both internal and external cues, integrating these signals to coordinate behavior and physiology. Mating interactions can promote dramatic changes in neuroendocrine cells which trigger successful copulation, ovulation, fertilization, and pregnancy. The neurons that transduce behavioral cues into neuroendocrine signals are distributed in a loose continuum along the medial ventral forebrain where they produce and secrete gonadotropin-releasing hormone (GnRH). In the past we have reported changes in GnRH-immunoreactive (GnRH-ir) cell numbers in brains of female musk shrews sacrificed during, and after, brief mating interactions. The purpose of the current study was twofold: first to determine which aspect of intracellular GnRH production is stimulated by behavioral interactions; second, to characterize the specific aspects of the social exchange that trigger GnRH production. We report that 1 h after copulation the production of proGnRH protein is stimulated. Non-copulatory behavioral interactions resulted in a rapid decrease in the numbers of neurons containing GnRH-ir peptide. This change was accompanied by an increase in the GnRH-ir fibers in the median eminence, but no surge in luteinizing hormone. These data suggest that behavioral interactions stimulate release of mature GnRH peptide from cell bodies followed by accumulation of available GnRH in cell terminals. Copulation triggers increased production of proGnRH in cell bodies. The data highlight the usefulness of behavioral paradigms for the examination of the dynamics of neuropeptide production.

Animals↗
PubMed2000

Anaesthetising Drosophila for behavioural studies.

The detrimental effect of anaesthesia by chilling or CO(2) on the mating behaviour of Drosophila melanogaster was investigated. Both agents significantly increased copulation latency, even when flies were given 20 h to recover from anaesthesia. CO(2) anaesthesia increased copulation latency more than anaesthesia by chilling. Delivery of a mechanical shock to the flies immediately before testing also increased copulation latency. These experiments demonstrate the sensitivity of insect behaviour to disruption by anaesthesia or rough handling. It is preferable to avoid anaesthetising flies that are to be used in behavioural studies.

Journal Article↗
PubMed1998

Effects of fadrozole on sexual displays and reproductive activity in the female canary.

We used fadrozole, a potent inhibitor of the aromatization of androgens to estrogens, to investigate the influence of estradiol on copulation solicitation displays (CSD) and reproductive activity in female canaries (Serinus canaria). Systemic injections of fadrozole during 10 consecutive days were effective in reducing plasma estradiol concentrations in adult female canaries submitted to photostimulation. Fadrozole provides a powerful tool for limiting an individual's exposure to estradiol, and the results of this study emphasize the influence of estradiol secretion in the regulation of behavioral transitions along the reproductive cycle of the female canary. When females were injected at the beginning of photostimulation, the emergence of copulation solicitation displays in response to conspecific songs was delayed. When females were injected later, after they were sexually active, the fadrozole treatment did not affect sexual displays. These results are consistent with the hypothesis that a threshold level of estradiol is critical to activate the neural circuitry mediating the copulation solicitation displays response in the female canary. They also suggest that the magnitude of sexual response is not related in a dose-dependent manner to estrogen concentrations observed during the period of sexual responsiveness. When females were injected at the beginning of photostimulation, egg-laying was delayed; when females were injected later, after they were sexually active, the fadrozole treatment dramatically reduced egg-laying and prevented incubation.

Animals↗
PubMed1997

Collection of semen and artificial insemination of alpacas.

Semen collection and artificial insemination have not yet been fully developed in the alpaca. Thus, we collected semen from 7 males using a modified artificial vagina placed inside a dummy. Forty adult female alpacas, previously induced to ovulate with hCG, were artificially inseminated with fresh undiluted semen by laparoscopy or by cervix. The Chisquare test was used to determine differences in the fertility rate of the 2 insemination methods. The mean duration of copulation, semen volume, sperm concentration and the percentages of live spermatozoa and normal spermatozoa were 21.6 min, 1.9 ml. 147,500/mm(3), 69.6% and 75.9%, respectively. There were 6.7% abnormal heads, 12.3% abnormal tails and 3.8% cytoplasmic droplets. The consistency of semen was viscous and formed a coagulum. The pH was 7.2, and the semen was milky white in color. The duration of copulation was comparable to natural copulation, and semen characteristics reflected those of the natural ejaculate. The percentage of pregnancy was 68%, with no differences due to method of semen deposition (laparoscopy, 67%; cervix, 73%).

Journal Article↗
PubMed2000

Mating behavior of bucks and does in goat operations under range conditions.

The objectives of this study were to characterize the mating capacity of bucks under range condition and assess the effect of mating frequency on flock fertility. Two adjacent flocks of crossbred goats (Criolloxdairy breeds; n=70 does, 5 bucks and 141 does, 4 bucks) were used in this study. The mating period was 16 and 20 days for each flock, respectively, in January and February, 1996. Mating activity of bucks and does was recorded day and night during the first 11 days of the breeding period. The combined data of both flocks showed a strong relationship between number of goats in estrus and the average services of bucks (r=0.95; P<0.01). With an excess of estrous does, bucks on average copulated 9.1 times daily during the first 11 days of the mating period. Considering both flocks combined, does copulated on average 4+/-1.8 times through the estrus period, and they did so with an average of 2.2+/-1.3 different bucks. Sexual activity of bucks was greatest from sunset to midday. Number of services from different bucks did not affect pregnancy rate (81.4% for goats serviced by 1-2 bucks and 77.8% for goats serviced by 3-4 different bucks; chi(2)=0.25; P7 services, respectively; chi(2)=0.67; P0.05). Mean+/-S.D. daily liveweight loss of bucks during the entire mating period was 547+/-197 g. It was concluded that, with buck percentages higher than 3%, the number of ejaculations of bucks is linearly and positively related to number of females in estrus. Also, these findings indicate that neither number of copulations nor number of services from different bucks affected kidding rates.

Journal Article↗
PubMed2003

Estrous odors and sexually conditioned neutral odors activate separate neural pathways in the male rat.

Olfactory stimuli play important roles in sexual behavior. Previous studies have demonstrated that both estrous odors and initially neutral odors paired with copulation influence the sexual behavior of male rats. The present study examines the pattern of neural activation as revealed by Fos immunoreactivity (Fos-IR) following exposure to bedding scented with either a neutral odor (almond) paired previously with copulation, estrous odors or no odor. Following exposure to estrous odors Fos-IR increased in the accessory olfactory bulb, medial amygdala, medial bed nucleus of the stria terminalis, medial preoptic area, ventromedial hypothalamus, ventral tegmental area, and both the nucleus accumbens core and shell. Conversely, following exposure to the sexually conditioned odor Fos-IR increased in the piriform cortex, basolateral amygdala, nucleus accumbens core, and the anterior portion of the lateral hypothalamic area. In addition, following exposure to almond odor Fos-IR increased in the main olfactory bulb independent of its pairing with copulation. These patterns of Fos-IR following exposure to estrous or sexually conditioned odors were not influenced by either the addition or omission of the other type of odor. These findings demonstrate that estrous and sexually conditioned odors are processed by distinct neural pathways and converge in the nucleus accumbens core, suggesting that this structure has a unique role in processing sexual stimuli of both pheromonal and olfactory natures.

Animals↗