19 research outputs found
Neuroendocrinology of sexual behavior
One of the consequences of sexual behavior is reproduction. Thus, this behavior is essential for the survival of the species. However, the individual engaged in sexual behavior is rarely aware of its reproductive consequences. In fact, the human is probably the only species in which sexual acts may be performed with the explicit purpose of reproduction. Most human sexual activities as well as sex in other animals is performed with the aim of obtaining a state of positive affect. This makes sexual behavior important for wellbeing as well as for reproduction. It is not surprising, then, that sexual health has become an increasingly important issue, and that knowledge of the basic mechanisms controlling that behavior are urgently needed. The endocrine control of sexual behavior has been extensively studied, and although it is established that gonadal hormones are necessary, some controversy still exists concerning which hormone does what in which species. The brain areas necessary for sexual behavior have been determined in almost all vertebrates except the human. The medial preoptic area is crucial in males of all non-human vertebrates, whereas the ventromedial nucleus of the hypothalamus is important in females. Modulatory functions have been ascribed to several other brain areas
Silent or Vocalizing Rats Copulate in a Similar Manner
Published version. Source at http://doi.org/10.1371/journal.pone.0144164.Both male and female rats produce 50 kHz ultrasonic vocalizations (USVs) in the presence
of a sexual partner and during copulation. Previous studies showed that USVs have no
incentive value for rats. In this study, we evaluated the role of USVs in behavior during copulation.
Three groups of rats were used: sham males paired with sham females, devocalized
females paired with sham males, and sham females paired with devocalized males. During
the copulation test, the USVs emitted by the sham rat were recorded and the sexual behavior
of both the male and the female were observed. The results revealed that devocalized
and sham females showed similar patterns of sexual behavior and no difference was found
in the copulatory behavior of devocalized and sham males. Also the behavior of the partner
of a sham rat was comparable to the partner of a devocalized rat. In addition, almost no
changes in USVs emission were found in the 5 seconds before and/or after a copulatory
behavior. It can be concluded that USVs play no important role in rat copulatory behavior at
least in sexually naĂŻve rats
The Sexual Incentive Motivation Model and Its Clinical Applications
Sexual motivation (desire) requires the simultaneous presence of an active central motive state and
a stimulus with sexual significance. Once activated, sexual motivation leads to visceral responses and
approach behaviors directed toward the emitter of the sexual stimulus. In humans, such behaviors follow
cognitive evaluation of the context, including predictions of the approached individual’s response. After
successful approach and establishment of physical contact, manifest sexual activities may be initiated.
Sexual interaction is associated with and followed by a state of positive affect in most animals, whereas
aversive consequences may be experienced by humans. The affective reactions may become associated
with stimuli present during sexual interaction, and these stimuli may thereby alter their incentive properties. Here we show how the incentive motivation model can be used to explain the origins and possible
treatments of sexual dysfunctions, notably disorders of desire. We propose that associations formed
between negative outcomes of sexual interaction and the salient stimuli, for example, the partner,
underlies hypoactive desire disorder. Highly positive outcomes of sexual interaction enhance the incentive value of the stimuli present, and eventually lead to hyperactive sexual desire. Treatments aim to alter
the impact of sexual incentives, mainly by modifying cognitive processes
Male and female immediate fear reaction to white noise in a semi-natural environment: A detailed behavioural analysis of the role of sex and oestrogen receptors
In classical rodent anxiety models, females usually display lower anxiety than males,
whereas anxiety disorders are more prevalent in women. Perhaps this contradiction
is caused by the use of behavioural models with low external validity. Therefore,
we analysed immediate reactions to a sudden 90-dB white noise in a semi-natural
environment. We observed mixed-sex groups of rats for the 60 seconds preceding
noise onset and the first 60 seconds of exposure. White noise elicited fear-specific
behaviours hiding alone and huddling. It also increased exploratory and ambulatory
behaviours, although only in the burrow zone farthest from the open area. Thus,
in a semi-natural environment, white noise enhanced motor activity as a product
of fear-induced general arousal. Then, we compared male and female sexual, social,
exploratory and anxiety-related behaviour, and found little sex difference. This absence of behavioural effect, also observed in other studies, might be a result of our
study design, a familiar environment with an ecologically relevant social context.
Fear and anxiety responses are modulated by oestrogens through the activation of
oestrogen receptors α and β. Thus, in a third part of out study, we analysed how
treatment with either oil, oestradiol benzoate (EB), an agonist to the oestrogen receptor α (propylpyrazoletriol [PPT]) or β (diarylpropionitrile [DPN]) influenced female
behaviour. The effect of treatment was limited, both EB and PPT stimulated motor
activity in the open area before white noise, probably because of sexual activity.
PPT increased the probability of fleeing from the noise, and decreased the latency to
do so, which is consistent with a pattern of anxiogenic properties found in previous
studies. Contrary to reports in classical procedures, we failed to detect any effect of
DPN on immediate fear reactions in a semi-natural environment
Sexual incentive motivation and male and female copulatory behavior in female rats given androgen from postnatal day 20
Masculinization and feminization of rat sexual behavior has been supposed to occur during a short postnatal period. However, much data have made it evident that these processes may continue until adolescence. In the present study, we evaluated whether androgen treatment of females from postnatal day 20 and onwards could alter sexual motivation and behavior in a male direction. Juveniles were ovariectomized on day 20 and concurrently implanted with Silastic capsules containing either testosterone or dihydrotestosterone. Controls were implanted with an empty capsule. Tests for sexual incentive motivation and male sexual behavior were performed every fifth day when the females were between 50 and 75 days of age. At day 80, a test for female sexual behavior was performed. Females treated with testosterone approached a female sexual incentive far more than a male incentive, showing that sexual motivation had been changed in a male-like direction. Dihydrotestosterone had a similar, albeit smaller, effect. Females implanted with an empty capsule approached both incentives equally. Testosterone produced a high level of mounting behavior, whereas intromission-like behavioral patterns were rare and ejaculation-like behavior was absent. In the test for female sexual behavior, the testosterone-treated animals displayed a relatively high lordosis quotient, far above that displayed in females implanted with dihydrotestosterone or an empty capsule. It is concluded that treatment with an aromatizable androgen during the peripubertal-adolescent period masculinizes sexual motivation and partly sexual behavior. A non-aromatizable androgen weakly masculinize sexual motivation without enhancing male sexual behavior. It appears that simultaneous actions on androgen and estrogen receptors are needed for significant masculinization during the period studied here. Since the testosterone-treated females displayed lordosis, sexual behavior was not defeminized. In sum, these results suggest that sexual differentiation continues well into the peripubertal and adolescent periods
Rat ultrasonic vocalizations and novelty-induced social and non-social investigation behavior in a seminatural environment
Although rats are known to emit ultrasonic vocalizations (USVs), it remains unclear whether these calls serve an auditory communication purpose. For USVs to be part of communication, the vocal signals will need to be a transfer of information between two or more conspecifics, and with the possibility to induce changes in the behavior of the recipient. Therefore, the aim of our study was to investigate the role of USVs in adult rats’ social and non-social investigation strategies when introduced into a large novel environment with unfamiliar conspecifics. We quantified a wide range of social and non-social behaviors in the seminatural environment, which could be affected by subtle signals, including USVs. We found that during the first hour in the seminatural environment the ability to vocalize did not affect how quickly adult rats met each other, their overall social investigation behavior, their passive social behavior nor their aggressive behavior. Furthermore, the non-social exploratory behaviors and behaviors reflecting anxiety/stress-like states were also unaffected. These results demonstrated that a disability to vocalize did not result in significant disadvantages (or changes) compared to intact conspecifics regarding social and non-social behaviors. This suggests that other (multi)sensory cues are more relevant in social interactions than USVs
Because sex matters: The case of female sexual response
In recent years, the Food and Drug Administration approved two drugs for the treatment of hypoactive sexual desire disorder in premenopausal women which have been tested in preclinical tests with positive effects on some appetitive sexual behavior in female rats. Some years after their commercial release, the effectiveness of both drugs in women is not clear. In the present chapter, we present some considerations regarding preclinical studies of copulatory behavior, most of them conducted in female rats. Although knowledge of the neurobiological basis of copulatory behavior in the female rat is still growing, the extent to which these findings might be applied to women’s sexuality is unknown. On the other hand, sexual response in women is flexible and less hormone-dependent compared with men. Moreover, sociocultural factors deeply influence sexuality in women, and they might contribute to the development of sexual dysfunctions. Additionally, the kind of model that better describes sexual response in women seems to be individual and fluctuating. We briefly mentioned some of the most used methods for measuring genital arousal, putting out the need for developing better strategies to get objective and replicable results. We conclude that the contribution, if any, of animal models of sexual response in female rodents is modest. After the questionable approval and the lack of efficacy of drugs to treat sexual desire issues, it is necessary to realize that the more we understand the female sexual responses, developing better ways to evaluate them, the more we might explain, and eventually treat their dysfunctions
Behavioral response is absent under the mating competition in rats (Rattus norvegicus)
Sexually receptive female rats normally copulate with several males during estrus, and multiple paternity is common. Sperm competition is therefore likely to occur. One response to competitive mating is to enhance sperm output per ejaculation and another is to augment the number of ejaculations. The latter alternative requires more intense copulatory behavior. In studies in a seminatural environment we observed that male rats did not modify their behavior according to the intensity of competition, whereas observations from standard observation cages suggested that they do so. In order to further evaluate the potential response to competitive mating, we observed male rats copulating in a pair situation, i.e. one male and one female, and in a situation where three males simultaneously copulated with one female. In addition to sexual behavior, social interactions were quantified. It was found that the males in the multiple male condition prolonged mount and intromission latencies, and displayed a reduced number of mounts. There was no change in the number of preejaculatory intromissions or the ejaculation latency. The multiple mating did not affect non-sexual interactions with the female, whereas the female displayed more nose-offs and rejections when copulating with three males. It is concluded that mating competition does alter the initiation of copulation in the male rat, whereas copulatory behavior, i.e. intromission and ejaculation, remains unchanged
Evaluation of Sexual Behavior in Laboratory vs Seminatural Conditions
Sexual behavior is, by necessity, sexually dimorphic. Males transfer sperm to females, whereas females receive sperm from males. Discussions of sex differences in copulatory behavior are consequently trivial. However, the behaviors associated with copulation, for example mate choice or postcopulatory reactions, may well be similar in males and females. Such differences, even subtle, are far easier to observe in seminatural environments than in the standard laboratory cage. We will present examples of the use of seminatural environments in insects and rodents. Even though most studies of insect sexual behavior are performed in relatively simple laboratory procedures, there are also some studies performed in natural or seminatural conditions. We briefly describe the most common procedures used and mention the main results. It is noteworthy that insect studies focus on sexual approach behaviors, particularly the role of visual and olfactory stimuli in mate location. The actual copulatory behavior, i.e., how gametes are transferred from one individual to another, seems to be of less interest.
The sexual behavior of rats has traditionally been studied in heterosexual pairs, despite the fact that they often copulate in groups. Nevertheless, data obtained in the simplified environment have advanced knowledge of the endocrine and neurobiological control of sex behavior in a quite spectacular way. The understanding of the dynamics of the sexual interaction and the possible function of the many peculiarities of rat sexual behavior has not advanced to a similar degree. Studies in seminatural environments may provide valuable data concerning sociosexual interactions and how such interactions are modified by contextual events. Furthermore, observations made in an environment, which incorporates the basic features of rats’ natural habitat, offer some external validity. This is of importance when we want to generalize our results to contexts outside the laboratory, and it becomes of paramount important when we want to make inferences about behavior in other species, for example the human. We offer here a detailed description of an environment designed for studies of group-living rats, with notes on the observation procedure and the analysis of the large quantity of data generated in the environment
Sexual incentive motivation, sexual behavior, and general arousal: Do rats and humans tell the same story?
Sexual incentive stimuli activate sexual motivation and heighten the level of general arousal. The sexual motive
may induce the individual to approach the incentive, and eventually to initiate sexual acts. Both approach and
the ensuing copulatory interaction further enhance general arousal. We present data from rodents and humans in
support of these assertions. We then suggest that orgasm is experienced when the combined level of excitation
surpasses a threshold. In order to analyze the neurobiological bases of sexual motivation, we employ the concept
of a central motive state. We then discuss the mechanisms involved in the long- and short-term control of that
state as well as those mediating the momentaneous actions of sexual incentive stimuli. This leads to an analysis of
the neurobiology behind the interindividual differences in responsivity of the sexual central motive state.
Knowledge is still fragmentary, and many contradictory observations have been made. Nevertheless, we
conclude that the basic mechanisms of sexual motivation and the role of general arousal are similar in rodents
and humans