Effects Of Sexual Experience Research Articles

Nature and nurture of sexual partner preference: Teachings from prenatal administration of acetaminophen in male rats

The organizational-activational hypothesis indicates that activation of adult sexual behavior in males depends on organization of the masculine brain during the perinatal sensitive period. In the medial preoptic area such masculinization depends on a neuroendocrine cascade that includes exposure to testosterone, aromatization to estradiol, activation of estrogen receptors, synthesis of cyclooxygenase (COX), increase of prostaglandins, release of glutamate, and activation of AMPA receptors that result in the formation of more dendritic spines. Thus, in the present study we assessed the sexual partner preference (SPP) of adult male rats prenatally treated with acetaminophen (APAP), an analgesic/antipyretic drug that inhibits COX-2 and is commonly used and prescribed during pregnancy. Female rats received either saline (2 ml/kg s.c.) or APAP (50 mg/kg s.c.) every 12 h, during days 16–20 of pregnancy. At postnatal day PD60 half of the male offspring were exposed to sexual experience with receptive females during 5 trials, and the other half remained sexually naïve. At PD90 all them were tested for SPP with one sexually receptive female and one stud male. The results indicated that only APAP-naïve males failed to display SPP. However, APAP-experienced males displayed SPP for females. We discuss the effects of prenatal APAP in the disruption of unconditioned responses towards females (nature mechanisms), and the effects of sexual experience (nurture mechanisms) in the development of conditioned heterosexual preference.

Effects of Sexual Experience and Puberty on Mouse Genital Cortex revealed by Chronic Imaging.

The topographic map in layer 4 of somatosensory cortex is usually specified early postnatally and stable thereafter. Genital cortex, however, undergoes a sex-hormone- and sexual-touch-dependent pubertal expansion. Here, we image pubertal development of genital cortex in Scnn1a-Tg3-Cre mice, where transgene expression has been shown to be restricted to layer 4 neurons with primary sensory cortex identity. Interestingly, during puberty, the number of Scnn1a+ neurons roughly doubled within genital cortex. The increase of Scnn1a+ neurons was gradual and rapidly advanced by initial sexual experience. Neurons that gained Scnn1a expression comprised stellate and pyramidal neurons in layer 4. Unlike during neonatal development, pyramids did not retract their apical dendrites during puberty. Calcium imaging revealed stronger genital-touch responses in Scnn1a+ neurons in males versus females and a developmental increase in responsiveness in females. The first sexual interaction is a unique physical experience that often creates long-lasting memories. We suggest such experience uniquely alters somatosensory body maps.

Sexual Behavior and Synaptic Plasticity.

Although sex drive is present in many animal species, sexual behavior is not static and, like many other behaviors, can be modified by experience. This modification relies on synaptic plasticity, a sophisticated mechanism through which neurons change how they process a given stimulus, and the neurophysiological basis of learning. This review addresses the main plastic effects of steroid sex hormones in the central nervous system (CNS) and the effects of sexual experience on the CNS, including effects on neurogenesis, intracellular signaling, gene expression, and changes in dendritic spines, as well as behavioral changes.

No evidence that male sexual experience increases mating success in a coercive mating system

Several studies have shown that sexual experience can alter a male's mating behaviour to increase his future mating success. One explanation is that experienced males are better at courting females and inducing them to mate. Experienced males might also be better at identifying higher quality mates, although fewer studies have tested for this benefit. In both cases, however, these potential benefits of sexual experience might be partially offset by the energetic costs of courting and mating, which tend to reduce a male's subsequent ability to invest in sexually selected traits, and thereby reduce his future attractiveness and mating success (i.e. hasten the onset of reproductive senescence). Here we used the eastern mosquitofish, Gambusia holbrooki, to test whether sexual experience elevates male mating success. We housed recently matured males either with full mating access to females (experienced males) or in the visual and olfactory presence of females with which they could not mate (naive males). We then measured the strength of male mate choice for larger, more fecund, females, male mating behaviour (time spent chasing females and the number of copulation attempts) and insemination success. Experienced and naive males did not differ significantly in their mating behaviour and there was no effect of sexual experience on the likelihood of mating or on the number of sperm inseminated (although experienced males had a tendency to be less successful when performing gonopodial thrusts). Experienced males in two-choice trials were, however, significantly more likely to ‘inspect’ both females and had a significantly stronger preference for larger females. Finally, we measured male immune response and growth to test for any costs of the increased mating effort that is concomitant with greater experience. Experienced males had significantly slower postmaturation growth and a significantly weaker immune response than naive males.

Sexually experienced, but not naïve, female rats show a conditioned object preference (COP) for mating after a single training trial

Female rats with mating experience spend more time with the male rat, exhibit shorter contact-return latency to intromission, and display more proceptive behaviors in the male rat's compartment than during the first mating experience. The present study tested 1) whether mating induced conditioned object preference (COP) is possible with a single conditioning trial and 2) whether a preference is induced for an object associated with the first mating encounter or the fifth mating encounter in female rats. Ovariectomized, Long-Evans female rats were primed with estradiol benzoate + progesterone and either exposed to an empty paced mating chamber for 15 min (Naïve) or received a 15 intromission test of paced mating behavior (Experienced) on four separate occasions before undergoing the COP procedure. Experienced, but not Naïve, female rats developed a COP for a single mating bout, indicating that mating is highly rewarding for sexually experienced female rats. The findings raise questions about the effect of sexual experience on reward regions in the brain, the responsiveness of genital tissue, and learning mechanisms.

Remodeling of the number and structure of dendritic spines in the medial amygdala: From prepubertal sexual dimorphism to puberty and effect of sexual experience in male rats.

The posterodorsal medial amygdala (MePD) is a sexually dimorphic area and plays a central role in the social behavior network of rats. Dendritic spines modulate synaptic processing and plasticity. Here, we compared the number and structure of dendritic spines in the MePD of prepubertal males and females and postpubertal males with and without sexual experience. Spines were classified and measured after three-dimensional image reconstruction using DiI fluorescent labeling and confocal microscopy. Significantly differences are as follows: (a) Prepubertal males have more proximal spines, stubby/wide spines with long length and large head diameter and thin and mushroom spines with wide neck and head diameters than prepubertal females, whereas (b) prepubertal females have more mushroom spines with long neck length than age-matched males. (c) In males, the number of thin spines reduces after puberty and, compared to sexually experienced counterparts, (d) naive males have short stubby/wide spines as well as mushroom spines with reduced neck diameter. In addition, (e) sexually experienced males have an increase in the number of mushroom spines, the length of stubby/wide spines, the head diameter of thin and stubby/wide spines and the neck diameter of thin and mushroom spines. These data indicate that a sexual dimorphism in the MePD dendritic spines is evident before adulthood and a spine-specific remodeling of number and shape can be brought about by both puberty and sexual experience. These fine-tuned ontogenetic, hormonally and experience-dependent changes in the MePD are relevant for plastic synaptic processing and the reproductive behavior of adult rats.

Effects of Sexual Experience on Psychostimulant- and Opiate-Induced Behavior and Neural Plasticity in the Mesocorticolimbic Pathway.

Many factors, including social elements, influence drug addiction in humans and can be modeled in laboratory rodents. In general, the presence of social reward is protective against drug abuse and the absence or removal of social reward in both humans and rodents increases vulnerability to drug addiction. The current review chapter is focused on studies from our lab that have examined the effects of sociosexual behavior in male rats on drug-induced behaviors, including changes in both psychostimulant and opiate behavior. Furthermore, we review the underlying neural mechanisms by which these effects occur. Together, these results may help elucidate the neural mechanisms underlying the interaction between social and drug rewards and the mechanisms by which a loss of social rewards increase the vulnerability to drug addiction development.

Effects of Sexual Experience on Sexual Motivation in Copulatory Behavior in Male Rats

The effects of sexual experience on the behavior of one-year-old male Wistar rats in conditions excluding direct interaction and in conditions of direct contact with potential sexual and social partners were studied. Interest in a social partner on the other side of a partition was most strongly demonstrated by sexually experienced males, while sexually naive males showed the greatest interest in conditions of direct contact. All males showed maximum activity levels in the presence of a receptive female. Sexual experience in males had no effect on the motivational component of male sexual behavior, i.e. sexual excitation: the levels of sexual motivation in the presence of a receptive female were identical in sexually naive and experienced male rats. However, sexual experience produced fundamental changes in the nature of the consumatory stage of male sexual behavior on interaction with a receptive female, significantly increasing its expression. There were increases in measures of copulatory behavior such as the numbers of mountings and intromissions while the latent periods of their appearance decreased. There was also an increase in the proportion of males demonstrating elements of copulatory behavior in relation to partners of predominantly social significance.

Neuroplasticity in the Mesolimbic System Induced by Natural Reward and Subsequent Reward Abstinence

Natural reward and drugs of abuse converge on the mesolimbic system, where drugs of abuse induce neuronal alterations. Here, we tested plasticity in this system after natural reward and the subsequent impact on drug responses. Effects of sexual experience in male rats on behavioral sensitization and conditioned place preference associated with d-amphetamine (AMPH) and Golgi-impregnated dendrites and spines of nucleus accumbens (NAc) cells were determined. Moreover, the impact of abstinence from sexual behavior in experienced males on these parameters was tested. First, repeated sexual behavior induced a sensitized locomotor response to AMPH compared with sexually naive control subjects observed 1, 7, and 28 days after last mating session. Second, sexually experienced animals formed a conditioned place preference for lower doses of AMPH than sexually naive males, indicative of enhanced reward value of AMPH. Finally, Golgi-Cox analysis demonstrated increased numbers of dendrites and spines in the NAc core and shell with sexual experience. The latter two alterations were dependent on a period of abstinence of 7-10 days. Sexual experience induces functional and morphological alterations in the mesolimbic system similar to repeated exposure to psychostimulants. Moreover, abstinence from sexual behavior after repeated mating was essential for increased reward for drugs and dendritic arbors of NAc neurons, suggesting that the loss of sexual reward might also contribute to neuroplasticity of the mesolimbic system. These results suggest that some alterations in the mesolimbic system are common for natural and drug reward and might play a role in general reinforcement.

Sexual experience did not affect the long-term sexual behavior inhibition of male rats treated with fluoxetine

Antidepressants, including tricyclics, monoamine oxidase inhibitors and selective serotonin reuptake inhibitors cause sexual dysfunctions such as decreased sexual desire, erectile difficulties, and delayed ejaculation. Studies have shown that treatment with fluoxetine inhibits several components of sexual behavior in male rats. It is known that sexual experience improves the sexual behavior of male rats. Thus, the effects of sexual experience were examined in male rats during long-term treatment with fluoxetine or vehicle. Rats treated with 10mg/kg fluoxetine or vehicle daily (28 days) were observed for sexual behavior at the 14th, 21st, and 28th day of treatment. Long-term administration of fluoxetine increased the mount latency in control rats in the first session; no differences were observed in other parameters on the same day. Still in the control group, the mount and intromission latencies gradually decreased, whereas the number of intromissions and ejaculations increased over the sessions. The group in long-term treatment with fluoxetine also showed reduced mount and intromission latencies, although latencies remained significantly higher as compared to the control group. Fluoxetine-treated rats showed increased mount and intromission rates on the 28th day of treatment in relation to the first day. These data suggest that the impairment caused by long-term treatment with fluoxetine persists throughout the sessions despite the rats' sexual experience.

Sexual experience did not affect the long-term sexual behavior inhibition of male rats treated with fluoxetine.

Antidepressants, including tricyclics, monoamine oxidase inhibitors and selective serotonin reuptake inhibitors cause sexual dysfunctions such as decreased sexual desire, erectile difficulties, and delayed ejaculation. Studies have shown that treatment with fluoxetine inhibits several components of sexual behavior in male rats. It is known that sexual experience improves the sexual behavior of male rats. Thus, the effects of sexual experience were examined in male rats during long-term treatment with fluoxetine or vehicle. Rats treated with 10mg/kg fluoxetine or vehicle daily (28 days) were observed for sexual behavior at the 14th, 21st, and 28th day of treatment. Long-term administration of fluoxetine increased the mount latency in control rats in the first session; no differences were observed in other parameters on the same day. Still in the control group, the mount and intromission latencies gradually decreased, whereas the number of intromissions and ejaculations increased over the sessions. The group in long-term treatment with fluoxetine also showed reduced mount and intromission latencies, although latencies remained significantly higher as compared to the control group. Fluoxetine-treated rats showed increased mount and intromission rates on the 28th day of treatment in relation to the first day. These data suggest that the impairment caused by long-term treatment with fluoxetine persists throughout the sessions despite the rats' sexual experience.

Sexual reward in male rats: Effects of sexual experience on conditioned place preferences associated with ejaculation and intromissions

Various behavioral models and studies have provided evidence suggesting that male rat sexual behavior has rewarding and reinforcing properties. However, there is little information regarding the rewarding values of the different components of sexual behavior. Therefore, this study used a conditioned place preference (CPP) paradigm to address whether ejaculation and intromissions differ in their rewarding incentive values. We also addressed whether the differential rewarding values were dependent on prior sexual experience. Sexually naïve and experienced males received one pairing of either intromissions or ejaculation with one of the chambers in the CPP box. The amount of time spent in each chamber of the CPP apparatus after conditioning was then measured. Both sexually naïve and sexually experienced males formed a CPP for ejaculation, while only sexually naïve, and not sexually experienced, males formed a CPP for intromissions. Moreover, in sexually naïve males, multiple pairings of ejaculation with the designated chamber resulted in a CPP relative to the control chamber paired with display of intromissions. These data support the hypothesis that there is a hierarchy of rewarding sexual behavior, with ejaculation being the most rewarding component, and that the rewarding incentive value of other components of sexual behavior is dependent upon prior sexual experience.

The effects of sexual experience and estrus on male-seeking motivated behavior in the female rat

Ovariectomized (OVX) female rats were trained to traverse a straight alley and return to a goal box where they had previously encountered a male rat, a female rat or an empty goal box. The time required to run the alley was used as an index of the subjects' motivation to re-engage the goal box target. Subjects were tested in both estrus and non-estrus, first sexually naïve and then again after sexual experience. Female rats ran most quickly for a male target, most slowly for an empty goal box, and at intermediate speeds for a female target. Sexual experience tended to slow run times for all but male targets. Estrus enhanced approach behavior for males and an empty goal box, but tended to slow the approach toward females, both before and after sexual experience. This latter finding was further investigated in a second experiment in which sexually naïve OVX females were tested during estrus and non-estrus in a locomotor activity apparatus, a runway with an empty goal box, and an open field. Estrus produced no changes in spontaneous locomotion either in the activity box or the open field, but decreased run times in the alley and increased the number of center-square entries in the open-field. Thus, estrus produces increases in sexual motivation that selectively enhance exploratory, presumably male-seeking behavior, but not simple spontaneous locomotion.

Effects of sexual experience on conspecific odor preference and male odor-induced activation of the vomeronasal projection pathway and the nucleus accumbens in female rats

In the present study in estrogen–progesterone primed ovariectomized female rats, we examined the expression of a preference for male odors and male odor-induced Fos immunoreactivity throughout the vomeronasal projection pathway and the nucleus accumbens (NAcc), using both sexually experienced and sexually naive subjects. Female rats significantly preferred airborne odors and soiled bedding from sexually active males over those from estrous females, irrespective of the presence or absence of prior sexual experience. On the other hand, the brain regions in which exposure to male-soiled bedding significantly increased Fos expression were different between sexually experienced and sexually naive subjects. Significant increment of Fos expression in the posterior-dorsal medial amygdala (MePD) and the bed nucleus of stria terminalis (BNST) in forebrain, as well as the accessory olfactory bulb, was observed in both groups of subjects. Fos expression in the anterior-dorsal medial amygdala (MeAD), the medial preoptic area (mPOA) and the NAcc core, however, was significantly increased only in the sexually experienced subjects. These results suggested that male odor-induced activations of the MePD and/or the BNST, but not of the MeAD, the mPOA and the NAcc core, are required for the expression of a male-directed odor preference in female rats.

Effects of sexual experience on conspecific odor preference and estrous odor-induced activation of the vomeronasal projection pathway and the nucleus accumbens in male rats

Male rats prefer odors from estrous females to those from sexually active males. Several studies, however, have demonstrated that prior sexual experience was required to develop the preference for estrous odor. Immunohistological methods for visualizing Fos protein have been shown that in sexually experienced male rats, estrous odors activate brain areas throughout the vomeronasal projection pathway (VN pathway) and the nucleus accumbens (NAcc). In the present study, we examined the contribution of prior sexual experience to the estrous odor-induced neuronal activation of these brain areas in relation to the development of the preference for estrous odor. Sexually experienced testosterone-implanted castrates showed the preference for the odor from an estrous female as opposed to the odor from a sexually active male. In these subjects, significant increment of Fos-like immunoreactivity (Fos-Li) after exposure to estrous female soiled bedding was observed in all brain regions examined, confirming the results of previous studies. Sexually naïve subjects, on the other hand, did not show the preference for estrous odor and the significant increment of Fos-Li was observed only in the accessory olfactory bulb (AOB) and the posterior–dorsal medial amygdala (MePD) of the VN pathway. These results suggested that sexual experience is required for the estrous odor-induced activation of more central portions of the VN pathway, such as the medial preoptic area (mPOA) and the bed nucleus of the stria terminalis (BNST), and the NAcc. The activation of some of these brain regions, therefore, is probably involved in the development of the preference for estrous odor.

Induction of Fos immunoreactivity in oxytocin neurons in the paraventricular nucleus after female odor exposure in male rats: effects of sexual experience.

1. We examined whether oxytocin (OT) neurons in the paraventricular nucleus of the hypothalamus (PVN) were activated by estrus female odor and sexual contact in sexually naïve and experienced Long-Evans rats. 2. Male rats were not presented to anesthetized estrus females (control) or presented to the females without (exposure to the female odor without sexual contact) or with direct contact (exposure to the female odor with sexual contact). 3. Exposure to the female odor with sexual contact significantly increased OT neurons with Fos-ir in both males. Exposure to the female odor without contact increased OT neurons with Fos-immunoreactive cells (Fos-ir) in sexually experienced males but not in naïve males, suggesting that the female odor without sexual contact activated the oxytocinergic neuronal system in the PVN in the experienced males. 4. Therefore, exposure to the estrus female odor itself may exert different effects on sexually naïve and experienced males.

Do female broiler breeder fowl display a preference for broiler breeder or laying strain males in a Y-maze test?

In recent years, the commercial broiler breeder industry has reported problems of male aggression towards females [Millman, S.T., 1999. An investigation into extreme aggressiveness of broiler breeder males. Unpublished PhD Thesis, University of Guelph]. Although this aggression is shown by the males and is apparently a defect in their behaviour [Millman, S.T., Duncan, I.J.H., 2000. Strain differences in aggressiveness of male domestic fowl in response to a male model. Appl. Anim. Behav. Sci. 66, pp. 217–233], it is also possible that it stems in some way from the females. For example, broiler breeder females may not be receptive to male courtship advances, and may avoid males, thus causing frustration in otherwise normal males. The objective of this study was to examine mate preference by broiler breeder females and the effects of sexual experience on preference. A total of 24 mature, broiler breeder females were individually tested in a Y-maze, with females choosing between a broiler breeder male and a laying strain male. Females were tested using male models and tethered live males, both when the females were sexually inexperienced and after they had been housed with broiler breeder or laying strain males for 6 weeks. Females did not display a male-strain preference when tested with models, but sexually experienced females displayed some evidence of a preference for laying strain males in tests with live males, which did not reach statistical significance ( P<0.10). Live males were a stronger attractant for sexually experienced females than were models ( P<0.005). Individual females tested with the same pair of males showed different preferences, suggesting females used male behaviour as a basis for their choices, and not male morphology. In conclusion, we found no evidence that broiler breeder females inherently discriminate against broiler breeder males.

Reliability and Validity of the Sexual Self-Esteem Inventory for Women

The Sexual Self-Esteem Inventory for Women (SSEI-W) was developed to assess affective reactions to self-appraisals of sexuality. The 81-item measure contains five subscales, each of which reflects a domain of sexual self-esteem: Skill/Experience, Attractiveness, Control, Moral Judgement, and Adaptiveness. Using a college student sample, reliability analyses indicated that the subscales have high internal consistency. Construct validity was assessed by testing hypotheses regarding the effects of sexual experience, relationship commitment, sex guilt, and global self-esteem on sexual self-esteem. In most cases, as predicted, specific SSEI-W subscales were most strongly associated with specific constellations of predictor variables. These findings suggest that different domains of sexual self-esteem are affected by different situations and provide evidence for the multi-dimensionality of sexual self-esteem.

Social cognition and social structure in the prediction of cervical screening uptake

A random sample of women (N = 614) was interviewed following a campaign to encourage uptake of cervical screening. Previously non‐screened women were sent leaflets explaining the purpose of cervical screening together with up to three invitation letters to encourage attendance. Following the campaign, socio‐demographic characteristics of women remaining unscreened were compared with those of the screened population to assess the role of service provision in ameliorating differences in uptake. A small social class differential existed after the call programme. The study tested the utility of cognitions specified by the Health Belief Model to distinguish participants versus non‐participants and to mediate the effects of marital status, social class and sexual experience in screening uptake. Overall, health beliefs, socio‐demographic variables and number of sexual partners accounted for 57 per cent of variance in screening uptake. Screened women reported greater sexual experience and the effects of sexual experience on screening uptake were mediated by perceived susceptibility, perceived costs, perceived benefits and normative belief. The effects of social class on screening uptake were mediated by perceived susceptibility, perceived aversiveness of the test procedure and perceived aversiveness of a positive result, suggesting persistent cultural barriers to uptake. No evidence was found to suggest that practical difficulties in attendance contributed to socio‐demographic differentials. These findings suggest that where repeated opportunities for screening are provided by the health service, health beliefs are sufficient to identify those who take up screening.

The effect of sexual experience on the attitudes of medical students to learning gynecological examinations.

The influence of sexual experience and gender on the attitudes of medical students to the methods of teaching the gynecological examination was studied. Data were obtained by questionnaire from students who had completed their obstetric/gynecological and family medicine clinical terms. Two hundred and eighty-six students agreed to participate. Ninety of the male students (53%) and 63 (54%) of the female students had experienced sexual intercourse. Students, male and female, who were sexually experienced felt they were more able to conduct a gynecological examination with sensitivity, put the woman at ease and to explain to the women what was being done and why. Male students who had not experienced sexual intercourse felt less able to perform a speculum examination, to do a Papanicolaou smear or be able to detect an abnormality. There were no gender differences between the preferred methods of learning to conduct a gynecological examination but non-sexually experienced students ranked higher the examination of a woman under anesthesia. The suggestion of student volunteers was more acceptable to sexually experienced women and non-sexually experienced male students. Students varied in their response to being volunteers for students learning to conduct vaginal or rectal (if male) examinations. If only the same sex were present 31% of non-sexually experienced male students would possibly volunteer for rectal examination and 39% of sexually experienced female students for vaginal examination. Sexual experience influences students' choice of methods for learning to conduct a gynecological examination.