Components Of Sexual Behavior Research Articles

Re-feeding and the restoration of odor attractivity, odor preference, and sexual receptivity in food-deprived female meadow voles

Food-deprived meadow voles were used to test predictions of two hypotheses associated with the recovery of sexual behaviors following re-feeding. Specifically, we tested between the body weight set point and metabolic fuels hypotheses. To do so, we determined whether the body weight of previously food-deprived female voles had to return to pre-food deprivation levels before they would recover their sexual behaviors. The body weight set point hypothesis predicts that food-deprived females that were re-fed will recover their sexual behavior after they return to their original body weight. In contrast, the metabolic fuels hypothesis predicts that food-deprived females that were re-fed will recover their sexual behavior before they return to their original body weight. That is, when the females are in positive energy balance. To distinguish between these two hypotheses, female voles were food deprived for 24 h, which is sufficient to inhibit all three components of sexual behavior. The food-deprived females were then supplied ad libitum food for 0 h, 24 h, 48 h, 72 h, or 96 h and weighed. Females were then tested for their sexual behaviors (odor attractivity, odor preference or proceptivity, sexual receptivity). Re-feeding for 48 h was sufficient to restore odor attractivity, 72 h was sufficient to restore odor preferences for opposite sex conspecific odors, and 96 h was sufficient to restore sexual receptivity to those similar to that of females that were not food deprived. The time-points that the behaviors were recovered were prior to voles recovering their initial body weight. Thus, the data support the metabolic fuels hypothesis.

Central regulation of ejaculation

Ejaculation is a reflex mediated by a spinal control center, referred to as a spinal ejaculation generator. This spinal ejaculation generator coordinates sympathetic, parasympathetic and motor outflow to induce the two phases of ejaculation, i.e., emission and expulsion. In addition, the spinal ejaculation generator integrates this outflow with inputs that are related to the summation of sexual activity prior to ejaculation that are required to trigger ejaculation. Recently, a group of spinothalamic neurons in the lumbar spinal cord (LSt cells) were demonstrated to comprise an integral part of the spinal ejaculation generator. Specifically, lesions of LSt cells completely ablate ejaculatory function. Moreover, LSt cells are activated following ejaculation, but not following other components of sexual behavior. Furthermore, based on their relationship with autonomic nuclei, motoneurons and genital sensory inputs, LSt cells are also in the ideal anatomical position to integrate sensory inputs and autonomic and motor outflow. Additionally, the spinal ejaculation generator is under inhibitory and excitatory influence of supraspinal sites, including the nucleus paragigantocellularis (nPGi), the paraventricular nucleus of the hypothalamus (PVN) and the medial preoptic area (MPOA). Finally, sensory information related to ejaculation is processed in the spinal cord and brain, possibly contributing to the rewarding properties of ejaculation. One candidate pathway for relay of ejaculation-related cues consists of LSt cells and their projections to the parvocellular subparafascicular thalamic nucleus. Moreover, neural activation specifically related to ejaculation is observed in the brain and may reflect of processing of ejaculation-related sensory cues.

Central regulation of ejaculation

Ejaculation is a reflex mediated by a spinal control center, referred to as a spinal ejaculation generator. This spinal ejaculation generator coordinates sympathetic, parasympathetic and motor outflow to induce the two phases of ejaculation, i.e., emission and expulsion. In addition, the spinal ejaculation generator integrates this outflow with inputs that are related to the summation of sexual activity prior to ejaculation that are required to trigger ejaculation. Recently, a group of spinothalamic neurons in the lumbar spinal cord (LSt cells) were demonstrated to comprise an integral part of the spinal ejaculation generator. Specifically, lesions of LSt cells completely ablate ejaculatory function. Moreover, LSt cells are activated following ejaculation, but not following other components of sexual behavior. Furthermore, based on their relationship with autonomic nuclei, motoneurons and genital sensory inputs, LSt cells are also in the ideal anatomical position to integrate sensory inputs and autonomic and motor outflow. Additionally, the spinal ejaculation generator is under inhibitory and excitatory influence of supraspinal sites, including the nucleus paragigantocellularis (nPGi), the paraventricular nucleus of the hypothalamus (PVN) and the medial preoptic area (MPOA). Finally, sensory information related to ejaculation is processed in the spinal cord and brain, possibly contributing to the rewarding properties of ejaculation. One candidate pathway for relay of ejaculation-related cues consists of LSt cells and their projections to the parvocellular subparafascicular thalamic nucleus. Moreover, neural activation specifically related to ejaculation is observed in the brain and may reflect of processing of ejaculation-related sensory cues.

Systemic and intracerebroventricular injections of vasotocin inhibit appetitive and consummatory components of male sexual behavior in Japanese quail.

The authors investigated the behavioral actions of vasotocin (VT) in castrated testosterone-treated male Japanese quail. The appetitive and consummatory components of sexual behavior as well as the occurrence frequency of crows were inhibited, in a dose-dependent manner, by injections of VT. The authors observed opposite effects after injection of the V1 receptor antagonist, dPTyr(Me)AVP. Lower doses of VT were more active after central than after systemic injection, and effects of systemic injections of VT were blocked by a central injection of dPTyr(Me)AVP. The behavioral inhibition was associated with a modified diuresis after systemic but not central injection. These results provide direct evidence that VT affects male sexual behavior in quail by a direct action on the brain independent of its peripheral action on diuresis.

Timing of Proceptive and Receptive Behavior of Female Goats in Relation to the Preovulatory LH Surge.

The temporal relation between the luteinizing hormone (LH) surge and the occurrence of two components of sexual behavior was investigated in female goats. Behavior observation and blood sampling were carried out every 2-6 hr from 26 hr before through 116 hr after prostaglandin (PG) administration which was given to induce luteolysis during the mid-luteal phase. The preovulatory LH surge appeared 30-100 hr after PG injection, and it continued for 6.5 +/- 0.4 hr. Although the interval from PG injection to the onset of the LH surge differed considerably among individuals, the proceptivity (defined as an approach to a male with vigorous tail-swishing) and the receptivity (defined as an acceptance of male's mounting or copulation) occurred well synchronized with the LH surge in each female. The proceptivity and receptivity were observed from -7.4 +/- 1.7 hr to 16.8 +/- 1.5 hr and from -2.6 +/- 1.6 hr to 13.0 +/- 2.0 hr, respectively, with regard to the LH surge onset (0 hr). Thus the proceptivity appeared first and lasted longest, and the receptivity was always seen around the time of the LH surge suggesting an existence of causal relationship between these two preovulatory events. The present results support the view that the female goat has evolved an efficient behavioral strategy such that it actively attracts males before it becomes fully receptive of male's approach to mate, when the LH surge occurs simultaneously to ensure a high conception rate at the subsequent ovulation.

Effects of a muscarinic antagonist on various components of female sexual behavior in the rat.

The effects of the muscarinic antagonist scopolamine on lordosis, solicitation, pacing, approach, attractivity, and activity were evaluated in ovariectomized rats brought into sexual receptivity with estrogen and progesterone. Systemic (1 mg/rat) or intraventricular (10 micrograms bilaterally) administration of scopolamine significantly reduced the incidence of lordosis and solicitation behaviors and disrupted typical pacing of sexual contacts with a stimulus male. In addition, females avoided contact with a stimulus male, but not a stimulus female, following intraventricular infusion of scopolamine. The levels of general activity and frequencies of sexual contacts were similar in females treated intraventricularly with scopolamine and vehicle solutions. Consequently, scopolamine disrupted various components of sexual behavior, including lordosis, solicitation, pacing, and approach, without altering female attractivity or general activity.

Reciprocal relationships between pulsatile androgen secretion and the expression of mating behavior in adult male ferrets

The pulsatile secretion of androgen was similar over a 12-hr period in breeding male ferrets implanted with jugular catheters which either achieved an intromission with an estrous female or received no socio-sexual contact. This negative result contrasts with the previous demonstration ( Carroll, Erskine, and Baum, 1987, Endocrinology 121, 1349–1359) of a significant, delayed rise in mean plasma androgen concentrations in breeding male ferrets 5–12 hr after mating. Males used in that previous study had lower initial mean plasma levels of androgen and smaller testis diameters than the present males. We therefore asked whether differences in circulating androgen levels, characteristic of males in different phases of the seasonal breeding cycle, might affect the expression of mating behavior. Castrated males given 0, 0.2, 2.0, or 5.0 mg/kg of testosterone propionate (TP) showed dose-related increases in the expression of different components of sexual behavior, including neck gripping, mounting, and intromitting. Surprisingly, intromissive performance was significantly better in intact breeding males than in castrates given even the highest dosage of TP. These results suggest that ferrets' mating performance may vary with seasonal variations in androgen availability, and that the ability of males to exhibit a postcoital increase in the testicular secretion of androgen may be limited to the beginning or end of the breeding season, when circulating levels of androgen are relatively low. Mating-induced increments in androgen secretion at these times may enhance subsequent reproductive success by facilitating males' intromissive capacity, which is required for the induction of ovulation and optimal sperm transport in female partners.

Mesotelencephalic dopamine system and reproductive behavior in the female rat: Effects of ventral tegmental 6-hydroxydopamine lesions on maternal and sexual responsiveness.

The effects of lesions to the mesolimbic dopamine system on maternal and sexual behaviors in the female rat was assessed. Rat dams that were given ventral tegmental area microinfusions of 6-hydroxydopamine (6-OHDA) during lactation showed a persistent deficit in pup retrieval but were not impaired with respect to nursing, nest building, or maternal aggression. In addition, 6-OHDA-lesioned females failed to respond to amphetamine by showing locomotor hyperactivity. Administration of the dopamine blocker raclopride to neurologically intact dams also inhibited pup retrieval but had no effect on nursing. Females given 6-OHDA during pregnancy appeared completely unresponsive to pups, whereas no maternal deficits were seen in females that received 6-OHDA 8 weeks before parturition. Proceptive (hopping and darting) and receptive (lordosis) components of sexual behavior, assessed after ovariectomy and exogenous steroid hormone treatment, were not affected by mesolimbic 6-OHDA lesions.

Hypothalamic neuropeptide Y (NPY) in obese Zucker rats: Implications in feeding and sexual behaviors

Neuropeptide Y (NPY), a peptide of the pancreatic polypeptide family, is actually considered to be the most potent stimulator of food intake in rats when centrally injected. It has also suppressive effects on several components of sexual behavior. It was measured in discrete microdissected brain nuclei in obese hyperphagic Zucker fa/fa rats also characterized by a deficient reproductive function, as well as in their lean homozygous (Fa/Fa) and heterozygous (Fa/Fa) counterparts. When compared with the lean (Fa/Fa) rats, NPY concentrations were significantly increased in the obese rats in the arcuate nucleus-median eminence (ARCME, +300%), in the paraventricular (PVN, +60%), suprachiasmatic (SCH, +90%), accumbens (+100%) and supraoptic (+40%) nuclei, as well as in the median preoptic area (MPOA, +70%). As PVN is one of the most important nuclei involved in the control of food intake and one site of NPY action, the high levels found in this nucleus might be a major component at the origin of hyperphagia in the obese animals. Food intake might be overstimulated by a sustained production of NPY as shown by the high concentrations found in the ARCME. NPY might also intervene in the pattern of food intake, for NPY contents were also largely modified in the SCH, the nucleus regulating feeding periodicity and in the MPOA, which is possibly involved in the regulation of energy balance. Finally, as the MPOA is the only site of action of NPY on sexual behavior, the higher levels measured in this area might contribute to the defective reproductive function of the obese Zucker fa/fa rat.

The role of the Flehmen response in the behavioral repertoire of the stallion

The role of the Flehmen response in equine behavior was investigated under field and laboratory conditions. In Experiment 1, a field study made of five stallions on pasture with between three and eighteen mares each during the season indicated the following: 1) The Flehmen response was most frequently preceded by nasal, rather than oral, investigation of substances; 2) The stallions' rate of Flehmen varied with the estrous cycles of the mares; 3) The rate of Flehmen response did not show a variation with time of day; and 4) The Flehmen response was most frequently followed by marking behaviors rather than courtship behaviors. The results suggest that the Flehmen response is not an immediate component of sexual behavior, e.g., courtship of the stallion but may be involved in the overall monitoring of the mare's estrous cycle. Therefore the Flehmen response may contribute to the chemosensory priming of the stallion for reproduction. In Experiment 2 stallions were presented with urine or feces of mares in various stages of the reproductive cycle as well as with their own or other males' urine or feces. The occurrence of sniffing and Flehmen was used to determine the discriminatory ability of the stallions. Stallions can differentiate the sex of a horse on the basis of its feces alone, but cannot differentiate on the basis of urine. This ability may explain the function of fecal marking behavior of stallions.

A component analysis of the effects of DPAT on male rat sexual behavior

Male rat sexual behavior was examined in a variety of tests following a single acute IP injection of the serotonin1A (5-HT1A) receptor agonist 8-hydroxy-2-(di-n-propylamino)tetralin (DPAT). The objective was to determine the effects of 5-HT1A receptor stimulation on the components of sexual behavior (arousal/motivation, erection and ejaculation) using this prototypical 5-HT1A ligand. In the ex copula genital reflex test, DPAT dramatically inhibited ejaculation and the display of penile erections. When examined in the mating behavior test, DPAT caused a significant reduction in intromission frequency (IF), ejaculation latency (EL), intercopulatory intervals (ICI) and postejaculatory interval (PEI). The decrease in IF and EL indicated a lowering of the behavioral-ejaculatory threshold, while the reduction in ICI and PEI indicated a stimulation of two aspects of sexual arousal. Further tests, however, revealed complexities. Using the mounting test (with genital anesthesia) as an assessment of sexual arousal, no effect of DPAT was found. Collection and examination of the coagulated ejaculates resulting from mating (copulatory plugs) provided evidence of an impairment in ejaculation, as a result of DPAT treatment. The data suggests that 5-HT1A receptor stimulation lowers the behavioral-ejaculatory threshold despite inhibition of ejaculation in and ex copula; as well as stimulating specific aspects of sexual arousal. It remains to be determined whether the effects on arousal were either due to nonselectivity as currently believed or because 5-HT1A receptor stimulation affects alpha 2-adrenoceptor activity by some as yet undefined mechanism; and as a result modulates sexual arousal.

Inhibitory influence of corticotropin releasing factor on components of sexual behaviour in the male rat

Acute microinfusions of ovine corticotropine releasing factor (CRF) into the third cerebral ventricle (III vent.) of sexually experienced male rats produced a dose-dependent suppression of masculine sexual behaviour. This inhibition of male sexual performance induced by CRF could be reversed by simultaneous infusions of naloxone, the opiate receptor antagonist, which when infused without CRF facilitated copulatory performance. These findings suggest that CRF can exert drastic effects on male reproductive behaviour through mechanisms which involve the activation of opioid pathways within the central nervous system. This CRF-linked neurochemical signal may mediate some of the well-known deleterious effects of stressful and noxious stimuli on reproductive function.

Androgen influence on lateral hypothalamus in the male rat: Possible behavioral significance

The lateral hypothalamus and other structures in the forebrain were explored with microelectrodes in the male rat under urethane anesthesia before and after IV injections of testosterone. In the lateral hypothalamus, significant proportion of neurons responded after a few minutes to the hormonal increases by changes in firing rate. These responses could be attributed neither to a solvent effect nor to generalized changes in cerebral activity as indicated by EEG monitoring. The rapid onset implies that the steroid molecule exerted a non-genomic effect on target cells. The brain cells detected here were either such testosterone target cells or other neurons transsynaptically connected to them. All units tested with estradiol and testosterone reacted in the same way to both steroids, suggesting that testosterone acts after being aromatized into estradiol. This supports a possible role of these neurons in the regulation of male sexual behavior. Their involvement in the modulation of motivation during the appetitive component of sexual behavior, according to the hormonal state of the subject, is discussed.

Biotelemetry recording of the electrical activity of the hippocampus and amygdala during sexual behavior in the cat

Five male and five female cats were anesthetized, and electrodes were implanted in the dorsal hippocampus and the basolateral amygdala. After recovery, a paired female and male were placed in a large playroom in which recordings were taken via biotelemetry during sexual behavior. Each session lasted 4 h or four successful matings, whichever came first. Both amygdala 40-Hz activity and hippocampal rhythmic slow-wave activity (RSA) of 4-5 Hz were very prominent during sexual behavior. Hippocampal RSA was the dominant activity in both male and female cats during all components of sexual behavior except pelvic thrusts just prior to intromission, when hippocampal desynchronization dominated the records. Amygdala 40-Hz activity was the dominant activity in all female and three male cats during all aspects of sexual behavior. Two male cats showed no 40-Hz activity from the point of neck grip until release after intromission, presumably due to the interruption of airflow through nasal passages. The results are discussed in relation to contemporary theories regarding the behavioral correlates of hippocampal RSA and amygdala 40-Hz activity.

Comparison of some CNS effects of luteinizing hormone-releasing hormone and progesterone

Luteinizing hormone-releasing hormone (LHRH) has been reported to facilitate lordotic behavior in estrogen-primed ovariectomized (OVX) female rats in a manner similar to progesterone (P). This study compared P and LHRH with respect to their behavioral effects and site of action within the brain. The hormones were compared using two different components of sexual behavior, receptivity and proceptivity. To test for receptivity, OVX females were given behaviorally ineffective estradiol benzoate (EB) injections sc 48 hr before testing. They were then treated with either P, LHRH, or vehicle by various routes. Two and/or four hours later, receptivity (LQ) was measured. Treatments for the proceptivity test were similar except that a larger EP-priming dose, which facilitates preceptive behavior, was used. Four hours later, LQ and hopping, darting, and earwiggling were scored. In the receptivity test, sc administration of 1 mg P or 1 μg LHRH (but not 0.5 or 5.0 μg) significantly elevated LQ with respect to vehicle injection 4 hr after treatment. In the proceptivity test, 0.5, 1.0, and 5.0 μg of LHRH given sc failed to alter significantly either LQ or soliciting behavior. Progesterone facilitated both parameters. Implantation of crystalline P into the midbrain reticular formation (MRF) has been shown to elicit both the receptive and preceptive effects of the steroid. Microinjection of as much as 100 ng of LHRH in 1.0 μl saline into the same region failed to enhance lordotic behavior compared to saline injection alone, while a 200-ng intracerebroventricular dose significantly facilitated lordosis at 4 hr. The data indicate that LHRH does not induce proceptive behavior. The effects of peripherally administered LHRH on receptive behavior are similar but less pronounced than those of P. The two hormones elicit this effect from different sites in the brain.

Sexual behavior and testosterone in middle-aged male rats.

Various components of sexual behavior were compared in middle-aged (13 months) and young adult (3 months) male rats to ascertain the nature of behavioral differences and the role of testosterone (T) in these differences. Behavioral procedures included: 1) tests of mating behavior; 2) tests of mounting behavior with genital anesthetization that focused on sexual arousal; 3) tests of spontaneous seminal emission that focused on ejaculatory mechanisms. In Exp 1, sexually experienced or inexperienced middle-aged males showed evidence of reduced sexual arousal, with the inexperienced middleaged group demonstrating the greatest reduction. The two middle- aged groups did not differ in plasma T levels, but both had levels significantly below those of the young group. In Exp 2, spontaneous seminal emission was found to occur more often in middle-aged retired breeders than in young sexually inexperienced males. In Exp 3, the dose-response relationship of behavior and T was evaluated in groups of castrated middle-ag...

The effects of lesions of lateral tegmental noradrenergic neurons on components of sexual behaviour and pseudopregnancy in female rats

Lesions (electrolytic and neurotoxic, using 6-hydroxydopamine) have been made of the projections of medullary noradrenergic neurons in the ascending ventral noradrenergic pathway in female rats. The lesions caused major depletion of noradrenaline in sub-cortical structures, notably the hypothalamus. In behavioural tests, these lesions selectively impaired sexual receptivity, measured as lordosis responses, but did not abolish proceptivity (soliciting). The impaired behaviour is critically dependent on somatosensory stimulation generated by the male during a mount. So, too, is pseudopregnancy since stimulation of the uterine cervix during coitus is essential for the prolongation of luteal life which underlies it. The ability to induce a pseudopregnant state was also abolished by the same ventral noradrenergic pathway lesion. These data, together with supportive evidence from experiments using procaine anaesthesia, have led us to suggest an important function of subcortically projecting noradrenergic neurons in the central transmission and/or processing of somatosensory information in neuroendocrine systems. We also present data suggesting that the effects of noradrenergic neuron activity are dependent on dopaminergic mechanisms more directly concerned with the control of motivated behaviour and anterior pituitary function.

Sexual behavior and some of its physiological consequences in persistently estrous aged female rats

Sexual behavior and some of its consequences were assessed in female rats which, with advancing age, had come to exhibit persistent vaginal estrus (PVE). Sexual receptivity, defined by the animal’s readiness to exhibit lordosis when mounted, was comparable across all ages evaluated. However, sexual proceptivity, defined by measures indicative of the female’s seeking mating opportunities, was determined to be much suppressed in 18 to 20 month old PVE females compared to either younger cyclic females or 12 to 15 month old PVE females. Mating disrupted the PVE pattern. The length of time animals remained out of estrus was positively correlated with the number of intromissions achieved by the male. However, pregnancy was not observed in any of the PVE females and examination of their ovaries and the responses of their uteri to traumatization provided no evidence of progestational responses in these animals. The behavioral data indicate that with continued exposure to the hormonal conditions of PVE there is a suppression of systems mediating the proceptive components of sexual behavior in female rats. It is suggested that changes in the concentrations of pituitary and/or ovarian hormones reported to occur as PVE rats continue to age may account for these changes in behavior.

Induction of sexual behavior in ovariectomized rhesus females with 19-hydroxytestosterone

Eight sexually experienced long-term ovariectomized female rhesus monkeys were given tests of sexual behavior following treatment with 19-hydroxytestosterone (19-OH-T, 1 mg/day for 13 days), and their performance was compared with that following treatment with estradiol benzoate (EB, 10 μg/day for 13 days). Each female was tested for 10 min with each of nine adult males. Blood samples were taken on the last day of treatment with EB, at the end of the intervening 3-month period of no treatment, and on the last day of treatment with 19-OH-T. Blood levels of testosterone and estradiol were quantified by radioimmunoassay. Mean rate of presenting at a distance (proceptive behavior) was significantly higher ( P < 0.05) when they were treated with 19-OH-T, but the ratio of presents to male contacts (receptive behavior) was significantly higher ( P <0.05) when they were treated with EB. All other components of female sexual behavior were the same. Males displayed fewer annoyance responses (rejecting jerk, P < 0.05) when the females were treated with 19-OH-T than when they were treated with EB. All other male responses occurred with the same frequencies under the two female treatment conditions. Injection of 19-OH-T and EB both resulted in plasma testosterone and estradiol levels higher than those found in the untreated condition. Testosterone levels did not differ under the two treatments ( P > 0.05), but estradiol levels were higher under EB treatment than under 19-OH-T ( P < 0.05). This study suggests that both testosterone and estradiol are essential for maximum sexual performance and that various components of sexual behavior may be differentially influenced by the ratio of testosterone to estradiol in plasma.

Hormonal control of sexual behaviour in the male rat and its implications for other species

Renewed interest in the hormonal control of male sexual activity stems from the finding that 5ol-reduced metabolites of testosterone (e.g. dihydrotestosterone) are strongly androgenic in the castrated rat but do not support sexual behaviour. In contrast, androgen/ oestrogen intermediates such as 19-hydroxytestosterone and oestrogen itself maintain the arousal component of sexual behaviour but not intromission performance. This deficit is a consequence of reduced penile sensitivity since oestrogenic steroids fail to maintain penile spines which provide peripheral feedback. If oestrogen-treated castrates additionally receive dihydrotestosterone to restore normal penile morphology, normal sexual behaviour ensues. Hence, oestrogen plus dihydrotestosterone effectively substitute for testosterone in the male rat. Biochemical evidence supports this finding since testosterone is known to undergo aromatization to oestrogen in the hypothalamus of the male rat and Se-reduction peripherally. Whether the aromatization model of testosterone action is applicable to species other than the rat is currently a matter for speculation. In mice, guinea pigs and hamsters evidence is either contradictory or unclear. However, the rabbit appears to be like the rat and oestrogen also supports normal sexual activity in castrated red deer stags. Conversely, in the rhesus monkey dihydrotestosterone alone appears to be effective. Further studies are required to establish the generality of the aromatization hypothesis; this applies particularly to domesticated species. SENSORY ASPECTS OF THE SEXUAL BEHAVIOUR OF MARES . . J. VEECKMAN and F.O. ODBERG Rijksuniversiteit Gent, K.L. Ledeganckstraat 35, B-9000 Gent (Belgium)