Effects of postnatal exposure to cadmium on male sexual incentive motivation and copulatory behavior: Estrogen and androgen receptors expression in adult brain rat.

There are numerous evidence showing that cadmium (Cd) is an endocrine disruptor that exerts multiple toxic effects at different reproductive levels, including male sexual behavior (MSB). The effect of early exposure to Cd on sexual incentive motivation (SIM) and MSB in adult stage, and the immunoreactivity of receptors for hormones such as estrogens and androgens in brain regions that are relevant for the SIM and MSB display, have not been studied until now. The present study evaluated the effects of 0.5 and 1 mg/kg CdCl2 from day 1-56 of postnatal life on SIM and MSB in adults rats, as well as serum testosterone concentrations, Cd concentration in blood, testis, and brain areas, and the immunoreactivity in estrogen receptors (ER-α and -ß), and androgen receptor (AR) in the olfactory bulbs (OB), medial preoptic area (mPOA), and medial amygdala (MeA). Our results showed that both doses of Cd decreased SIM and MSB, accompanied by low serum concentrations of testosterone. Also, there was a significant reduction in immunoreactivity of ER-α and AR in mPOA, and a significant reduction in AR in MeA on male rats treated with Cd 1 mg/kg. These results show that exposure to high doses of Cd in early postnatal life could alter the correct integration of hormonal signals in the brain areas that regulate and display SIM and MSB in adult male rats.

Chronic irisin exposure decreases sexual incentive motivation in female rats.

Irisin is a novel myokine/adipokine that is released into the circulation in response to types of exercise and increases energy expenditure. Disorders in the endocrine system related to reproduction, which occur due to the chronic or excessive exercise, cause a decrease in women's sexual desire. However, the role of irisin hormone on sexual desire in women has not been elucidated. We hypothesized that chronic irisin exposure would decrease sexual incentive motivation for male partners by affecting the endocrine system in female rats. We tested this by quantifying and comparing of both sexual incentive motivation and active investigation for sexual partner, and also changes in the serum hormone levels in chronically irisin-treated female rats. As a result, chronic irisin exposure decreased the time spent near the male rat, male preference ratio, and male investigation preference ratio. Furthermore, serum testosterone and progesterone levels significantly decreased and estradiol levels increased while kisspeptin-1 levels were not changed by chronic irisin exposure in female rats. These data indicate that chronic irisin exposure may cause low sexual incentive motivation for opposite-sex partners in female rats via changes in reproductive hormones. The results suggest that irisin hormone may play a role in decreased sexual desire due to long-term exercise in women.

Sexual behaviour is impaired by the abused inhalant toluene in adolescent male rats.

Inhalant misuse is a worldwide problem, especially among adolescents. Toluene is the most widely misused inhalant. One hallmark of adolescence is the emergence of sexual behaviour, which can be affected by drug use. The aim of this study was to analyse the effects of toluene inhalation on different aspects of male rats' sexual behaviour using a binge pattern of exposure in adolescent rats. Male Wistar rats were individually exposed to air or 6,000 ppm toluene for 30 min (acute exposure; n = 8 each) or twice a day for 12 days (repeated exposure; n = 9 each) in static exposure chambers. Independent groups of sexually experienced, adolescent rats (postnatal day 63, PN63) were tested after acute toluene exposure for copulation, sexual incentive motivation or noncontact erections. Sexually naïve, adolescent rats (PN45-59) were repeatedly exposed to toluene and tested for sexual behaviour after completing the 1st, 3rd, 5th, 7th, 9th, 11th and 13th exposure sessions. Acute toluene exposure impaired copulatory performance, diminished sexual incentive motivation and delayed noncontact erection occurrence in sexually experienced rats. Repeated toluene exposure during adolescence completely inhibited the onset of copulatory behaviours in sexually naïve rats, at the time at which they should have appeared. However, once the inhalant exposure ended, copulatory responses appeared gradually, and animals attained a typical, stable copulatory pattern. In conclusion, acute toluene exposure impairs sexual behaviour in young, sexually experienced animals, while repeated toluene exposure during adolescence prevents the onset of copulatory behaviour, although this effect is transitory.

The role of estrogen G-protein coupled receptor 30 (GPR30) and sexual experience in sexual incentive motivation in male rats.

Male rats exhibit reductions in sexual motivation following systemic administration of drugs that inhibit the conversion of testosterone to estrogen, which indicates that estrogen signaling plays a role in male rat sexual motivation. Given that estrogen G-protein coupled receptor 30 (GPR30) is expressed in brain areas that are important for male sexual behaviors and endocrine function, the primary aim of the current study was to examine the role that GPR30 plays in sexual motivation in both sexually naïve and sexually experienced male rats. Following the final treatment with either a GPR30 antagonist (G-15) or vehicle control, male rats were placed into the center chamber of a larger three-chambered testing arena that was designed to assess sexual incentive motivation. A sexually receptive stimulus female rat and a stimulus male rat were individually confined to one of the two smaller chambers that were each separated by a perforated partition from the larger end chambers, which test rats had access to. Relative to vehicle treated rats, male rats treated with G-15 exhibited a reduction in the percentage of time spent in the vicinity of a sexually receptive female rat. Although G-15 reduced sexual incentive motivation independent of sexual experience, only sexually-naïve rats treated with G-15 did not exhibit a preference for the sexually receptive stimulus female rat. Collectively, these results indicate that interference with estrogen signaling at GPR30 reduces sexual motivation and that the lack of preference for a sexually receptive female rat over a male rat following G-15 treatment is abrogated by previous sexual experience.

An unknown male increases sexual incentive motivation and partner preference: Further evidence for the Coolidge effect in female rats.

The Coolidge effect is the resumption of copulatory behavior induced by a novel sexual partner that has been reported in several species. The term is also used in males when they resume mating when exposed to an unknown receptive female after they have reached sexual exhaustion. Only few studies have evaluated the Coolidge effect in females. In the present study we further evaluated this possibility using the sexual incentive motivation (SIM) and the partner preference (PP) tests. Ovariectomized rats were hormonally primed and allowed to mate for 1h controlling the sexual interaction (paced mating) or in a condition where they were unable to pace the sexual encounters. In the SIM and PP tests, females were exposed to the male with whom they had mated before (known male) or with an unknown, sexually experienced one (unknown male). Regardless whether they paced the sexual interaction, all females showed clear preference for the unknown male but females that paced the sexual contacts spent more time in the incentive zone of the unknown male than females that could not pace the sexual interaction. Similar results were observed in the PP test. Both groups of females spent more time in the compartment of the previously unknown male than in that of the known one, but received the same amount of sexual stimulation, i.e., mounts, intromissions and ejaculations from both males. No preference was found when the females were tested in the SIM test between an unknown male and a sexually receptive female. The results further support the existence of a Coolidge effect in female rats that is more apparent if they pace the sexual interaction.

Deficits in odor-guided behaviors in the transgenic 3xTg-AD female mouse model of Alzheimer׳s disease.

Alzheimer׳s disease (AD) is characterized by a number of alterations including those in cognition and olfaction. An early symptom of AD is decreased olfactory ability, which may affect odor-guided behaviors. To test this possibility we evaluated alterations in sexual incentive motivation, sexual olfactory preference, sexual olfactory discrimination, nursing-relevant olfactory preference and olfactory discrimination in female mice. We tested 3xTg-AD (a triple transgenic model, which is a "knock in" of PS1M146V, APPSwe, and tauP300L) and wild type (WT) female mice when receptive (estrous) and non-receptive (anestrous). Subjects were divided into three groups of different ages: (1) 4-5 months, (2) 10-11 months, and (3) 16-18 months. In the sexual incentive motivation task, the receptive 3xTg-AD females showed no preference for a sexually active male at any age studied, in contrast to the WT females. In the sexual olfactory preference test, the receptive WT females were able to identify sexually active male secretions at all ages, but the oldest (16-18 months old) 3xTg-AD females could not. In addition, the oldest 3xTg-AD females showed no preference for nursing-relevant odors in dam secretions and were unable to discriminate between cinnamon and strawberry odors, indicating olfactory alterations. Thus, the present study suggests that the olfactory deficits in this mouse model are associated with changes in sexual incentive motivation and discrimination of food-related odors.