Consequence Of Copulation Research Articles

Endogenous opioids mediate the sexual inhibition but not the drug hypersensitivity induced by sexual satiation in male rats.

Ejaculation promotes endogenous opioid release. Copulation to exhaustion produces several enduring behavioral and physiological changes, among which a long-lasting sexual behavior inhibition and generalized drug hypersensitivity are the most conspicuous. Because copulation to exhaustion involves multiple successive ejaculations, in this work we hypothesized that the endogenous opioids released by multiple ejaculations during the copulation to exhaustion process might mediate the abovementioned sexual satiation-induced changes. To test this hypothesis, sexually experienced male rats were injected with the opioid receptor antagonist naltrexone before copulation to exhaustion and were tested for sexual behavior or drug hypersensitivity 24 h later. The latter was assessed by the appearance of the flat body posture sign of the serotonergic syndrome, in response to doses of the 5-hydroxytryptamine-1A (5-HT1A) receptor agonist 8-hydroxy-2-di-n-propylamino-tetralin (8-OH-DPAT), lower than those normally inducing this sign. The effect of administering naltrexone to already sexually exhausted animals (i.e., 24 h after the sexual satiation process) on both responses was also tested. Results showed that endogenous opioids mediate the establishment and maintenance of the long-lasting sexual behavior inhibition but not the drug hypersensitivity (to 8-OH-DPAT) characteristic of sexually exhausted male rats. It is concluded that although both phenomena appear as a consequence of copulation to satiation and follow a same time course of recovery, they are produced by distinct mechanisms.

Learning in intimate connections: Conditioned fertility and its role in sexual competition.

BackgroundStudies of sexual conditioning typically focus on the development of conditioned responses to a stimulus that precedes and has become associated with a sexual unconditioned stimulus (US). Such a sexually conditioned stimulus (CS) provides the opportunity for feed-forward regulation of sexual behavior, which improves the efficiency and effectiveness of the sexual activity.Objective and DesignThe present experiments were conducted to provide evidence of such feed-forward regulation of sexual behavior in laboratory studies with domesticated quail by measuring how many fertilized eggs were produced by the female after the sexual encounter. During the conditioning phase, male and female quail received a conditioned stimulus paired with the opportunity to copulate with each other.ResultsSexual conditioning increased the number of eggs that were fertilized as a consequence of copulation, especially if both the male and the female were exposed to the sexual CS. This conditioned fertility effect occurred with a range of CS durations and CS types. The conditioned fertility effect also occurred in situations involving sexual competition. When two males copulated with the same female, DNA fingerprinting showed that the male whose sexual encounter was signaled by a sexual CS was responsible for most of the resulting offspring. Sexual conditioning also reduced the first-male disadvantage in fertilization that occurs when two males copulate with the same female separated by several hours. Another significant finding was that sexual conditioning attenuated the usual drop in fertilization rate that occurs when the same male copulates with two females in succession.ConclusionThese results show that sexual conditioning increases the number of offspring that are produced in both isolated male-female encounters and in situations that involve two males copulating with the same female or one male copulating with more than one female. By increasing fertilization rates, sexual conditioning can alter genetic transmission across generations and shape evolutionary change.

A finely tuned strategy adopted by an egg parasitoid to exploit chemical traces from host adults

Scelionid egg parasitoids can obtain reliable information on the presence of host eggs by discriminating host gender on the basis of chemical footprints of their co-evolved hosts, with a strong preference for the footprint left by host females. Based on the concept of dietary specialization and infochemical use in natural enemies, it could be predicted that host gender discrimination in specialist species belonging to the genus Trissolcus is further tuned to specific cues from distinctive chemical traces left by host females as a consequence of copulation and/or oviposition. To test this hypothesis we used the system Murgantia histrionica - Trissolcus brochymenae. Our results showed that the females of the egg parasitoid search intensely on chemical traces left on the substrate by host females that had mated but had not yet laid host eggs compared with the chemical traces left by virgin or parous host females. This preference for mated females that had not yet laid host eggs was strictly related to the transfer of sperm and associated substances from males to females during copulation. The compounds that mediated the arrestment response of T. brochymenae females are part of the host cuticle, and those that play a role as gender-specific cues seemed to be present in the legs of the host adult. This result represents an interesting new piece of information regarding the exploitation of indirect host-related cues by egg parasitoids. It reveals the existence of a finely tuned strategy that allows the parasitoid to find newly laid host eggs, as chemical traces left by mated host females that have not yet laid eggs are strongly correlated with the moment of oviposition.

Sex and the female rat

Dopamine release in the nucleus accumbens (NAcc) correlates with rewarding or reinforcing events, and has been studied extensively in the context of drug abuse, feeding, and sex. Using behavioral indicators and measurements of NAcc dopamine, it appears that sexual activity is rewarding for female rats only if they, rather then the males, are controlling the pace of the activity. Furthermore, when the female slows the pace of copulation by hopping, darting, and withdrawing, a progestational reflex is optimally activated and the likelihood of pregnancy is increased. In the May 1 issue of Journal of Neuroscience, it is shown that the critical factor for increases in NAcc dopamine is the timing of the copulatory stimuli, independent of whether the female is actively regulating its timing. The University of Michigan authors suggest that the dopamine system is activated as a consequence of copulation at the preferred time intervals, rather than specifically mediating reinforcing-seeking behaviors. L.O.

SPERM DEPENDENCE OF FEMALE RECEPTIVITY TO REMATING IN DROSOPHILA MELANOGASTER.

As a consequence of copulation, males of Drosophila melanogaster induce a variety of physiological and behavioral effects in the female. Egg production and oviposition are stimulated by products of the male's accessory glands (Kummer, 1960; Garcia-Bellido, 1964; Merle, 1968; Bumet et al., 1973), and female attractiveness and receptivity are both reduced following copulation. Changes in female attractiveness are mediated pheromonally. A change in pheromonal profile from courtship-eliciting to courtship-discouraging pheromones is induced during the first 3 min of (Tompkins et al., 1980; Tompkins and Hall, 1981; Venard and Jallon, 1980). The seminal fluid enzyme esterase-6 metabolizes the seminal fluid component cis-vaccenyl acetate to produce the antiaphrodisiac cis-vaccenyl alcohol (Mane et al., 1983). Behavioral effects of this metabolite on female attractiveness have been demonstrated and have been shown to be short-lived. There is a close correspondence between the time course of these behavioral effects and those first identified by Manning (1967) as the copulation effect. Manning (1962, 1967) also identified a on female receptivity which is longer lasting and causes females to remain unreceptive to male courtship. The strength of the sperm effect seems to be proportional to the number of sperm in storage (Gromko and Pyle, 1978; Gromko et al., 1984). The sperm effect is characterized behaviorally by the use of ovipositor extrusion to reject males, a behavior used only in very low frequency by virgin females (Connolly and Cook, 1973; Tompkins and Hall, 1981). The -or the sperm dependence of the return of female receptivity-is not evident when mated females are confined with second males continuously for 24 h (Newport and Gromko, 1984). In this paper we investigate the details of the sperm dependence of female receptivity within the context of an experimental design which allows females periodic interactions with second males. We also quantify the impact of sperm-dependent female receptivity on the reproductive outcome of double matings. We show that by causing females to delay remating, first males suffer very little reduction in reproductive success due to female remating.

Some consequences of copulation in Rhodnius prolixus

The increased egg production which accompanies mating is shown to be unaffected by allatectomy but is abolished by removal of neurosecretory cells. Part of the response to mating is due to an increased rate of oviposition, probably mediated by a myotropic factor released from neurosecretory cells. The retention of eggs results in a decrease in the size of the blood meal, which is partly responsible for the decrease in egg production among virgin females. However, a consideration of the feeding economy of females demonstrates that virgin females are much less efficient at converting their meal to eggs than are mated females.