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At least 163 records · Page 9Linked to original sources

Prepuberal MPOA lesions and housing condition: effects on rats' male sex behaviors.

After prepuberal male rats underwent either medial preoptic area (MPOA) lesions or sham surgeries, they were housed in all-male groups (SOC-X and SOC-S treatments) or isolation (ISO-X and ISO-S treatments). In the first mating test, SOC-X rats mounted and intromitted more than ISO-X, but not SOC-S, rats. In this and across mating tests, SOC-X did not differ from SOC-S rats in the proportion ejaculating; however, fewer ISO-X than ISO-S rats ejaculated. In the first ejaculatory test, MPOA-lesioned rats ejaculated less and had shorter PEIs than shams. No consistent effects on testes or seminal vesicles (SVs) were observed.

Animals↗

Estradiol, but not dihydrotestosterone, in the medial amygdala facilitates male hamster sex behavior.

In the male Syrian hamster, the medial amygdaloid nucleus (Me) and medial preoptic area (MPOA) are critical for expression of male mating behavior. These regions contain steroid receptor-containing neurons that transduce hormonal signals essential for copulation. In castrated males bearing an intracerebral steroid implant in the MPOA, testosterone or estradiol can facilitate sexual activity. However, DHT is without effect. Testosterone can also stimulate mating when implanted in the Me. The present study determined if estradiol or DHT had behavioral activity in the Me. Twenty adult male hamsters were selected for vigorous sexual behavior. Twelve weeks after castration, sexual behavior was assessed and each male received a single intracranial implant (23-gauge tubing packed with crystalline estradiol or DHT, n = 10 each) placed stereotaxically into posterior Me (MeP). Behavior was examined after surgery to determine if androgens or estrogens in MeP could stimulate sexual behavior above that observed after castration. Mating behavior in DHT-implanted males was not significantly different from castrates. However, males with estradiol implants displayed significantly more copulatory and noncopulatory sexual activity after surgery compared to males with DHT implants. These results suggest that testosterone facilitation of mating behavior in MeP is mediated by aromatization to estradiol, and that DHT is not behaviorally active in this nucleus.

Amygdala↗

Inhibition of male sex behavior by androgen receptor blockade in preoptic area or hypothalamus, but not amygdala or septum.

Inhibition of masculine copulatory behavior was previously demonstrated following systemic injections of hydroxyflutamide (OHF). In the present study, we examined the localization of the effects of this androgen receptor blocker by direct intracranial implantation of OHF into the medial preoptic area (MPOA), ventromedial nucleus of hypothalamus (VMN), medial amygdala (AME), and lateral septum (SEPT). Animals were implanted intracranially with crystalline OHF or cholesterol, and at the same time received two 10-mm testosterone-filled Silastic capsules SC. Tests for restoration of copulatory behavior were initiated 3 days later, and conducted twice weekly for 2 weeks. Implants of OHF into the MPOA were effective in preventing restoration of male sexual behavior. However, the most effective site was the VMN. Implants of OHF into the AME were only partially effective in stimulating male sexual behavior, whereas implants into the SEPT had no effect. The OHF was discontinued and 1 week later males were retested for sexual behavior. The majority of these animals ejaculated, indicating, that the effects of OHF are reversible. The result of this study demonstrate that the functional integrity of androgen receptors in some, but not all, androgen-concentrating brain loci is necessary for the expression of the complete pattern of male sexual behavior. These data lend support to the view that androgen receptor populations in specific brain loci differentially express proteins involved in mediating the masculine copulatory response.

Amygdala↗

Brain localization of cholinergic influence on male sex behavior in rats: agonists.

Cholinergic agonists were microinjected into either the lateral ventricle or the preoptic area of sexually experienced male rats. In Experiment 1 carbachol, injected into the lateral ventricles, delayed the initiation of sexual behavior. When injected into the preoptic area, carbachol again delayed the onset of copulation, but these delays were shorter than after ventricular injections. In addition, preoptic injections reduced the number of intromissions preceding ejaculation. In Experiment 2 ventricular injections of the muscarinic agonist oxotremorine again delayed initiation of sexual behavior and also slowed its rate. However, oxotremorine injections into the preoptic area, through cannulae angled to miss all ventricles, only decreased the number of intromissions preceding ejaculation. These data suggest that cholinergic synapses in proximity to the ventricles may decrease sexual arousal, while cholinergic mechanisms in or near the preoptic area may reduce ejaculatory threshold.

Animals↗

Brain localization of cholinergic influence on male sex behavior in rats: antagonists.

The muscarinic receptor antagonist scopolamine was microinjected into either the preoptic area or the lateral ventricle, preceding sexual behavior tests. In Experiment 1 unilateral ventricular injections of scopolamine delayed the initiation of copulation, while unilateral preoptic injections had no effect. In Experiment 2 bilateral injections into the preoptic area produced dose-related decreases in the percentages of animals intromitting and ejaculating. In Experiment 3 scopolamine, injected alone into the preoptic area, again decreased the percentages of animals mounting, intromitting, and ejaculating. The muscarinic agonist oxotremorine, injected alone into the preoptic area, decreased ejaculatory threshold (i.e., decreased the number of intromissions preceding ejaculation) as previously reported. Concurrent oxotremorine and scopolamine injections into the preoptic area were not different from vehicle; thus, scopolamine blocked oxotremorine's effect. These data suggest that some cholinergic activation of the preoptic area is critical for normal copulation, since bilateral blockade of muscarinic receptors there dramatically decreased the number of animals copulating. However, increased cholinergic activity there only reduced ejaculation threshold.

Animals↗

Sex behavior of male and female Wistar rats affected by the serotonin agonist 8-OH-DPAT.

Four experiments were carried out to test the stimulatory effects of 8-OH-DPAT on various aspects of "masculine" sexual behavior of male and female rats and on the sexual attractivity of male rats. In Experiment 1 8-OH-DPAT (0.2 mg/kg) stimulated ejaculation frequency in middle-aged (approx. 15 months old) males, both sexually inactive and active subjects. There was a coinciding decrease in total number of mounts, intromissions, intromissions to first ejaculation and latency to first ejaculation. In Experiment 2 the effects of two doses (0.2 and 0.4 mg/kg) 8-OH-DPAT on the first ejaculation cycle were investigated. Especially, the higher dose made a high percentage (45-55%) of males to ejaculate "prematurely," i.e., at the first or second intromission. Latency to ejaculation decreased. With the higher dose, 25-35% of the males ejaculated extravaginally. In Experiment 3 8-OH-DPAT did not make males more attractive for an estrous female than saline-treated males, as judged by the time spent in their vicinity. However, estrous females received much more ejaculations from the tethered 8-OH-DPAT males, with the lowest latencies to first ejaculation, than from the saline-treated males. In Experiment 4 8-OH-DPAT stimulated mounting behavior in female rats only when they were long-term treated with testosterone. In that condition also shortest latencies to first mount were found with 8-OH-DPAT treatment.

8-Hydroxy-2-(di-n-propylamino)tetralin↗

A direct magnocellular-preopticospinal pathway in goldfish: implications for control of sex behavior.

Neurons in the pars magnocellularis and gigantocellularis of the goldfish magnocellular preoptic nucleus concentrate horseradish peroxidase by retrograde transport following its placement into sectioned spinal cord. Implants at rostral levels labeled the greatest number of preoptic cells. The pathway demonstrated is primarily ipsilateral and appears equivalent to the paraventricular-spinal system of tetrapods. In goldfish it may control sperm release and other stereotyped reproductive responses.

Animals↗

Safe sex behavior in drug-addicted males as a function of object relations.

An inventory of sexual behavior was administered in a hospital detoxification program to 127 drug-addicted males, who also completed a modified form of the Defense Mechanisms Inventory (DMI) which yields a measure of object relations. Condom use was shown to be related to an object relations mode that typifies the individual who can structure reality and needs without requiring an integral aspect of "the other" in his approach. Standardization and factor analytic data are also presented for the DMI and the object relations measure for this population. The resulting pattern and the small effect size are discussed within the reality constraints of the addicted patient, as well as within the psychometric parameters inherent in psychoanalytic research.

Adult↗

Effects of paraventricular lesions on sex behavior and seminal emission in male rats.

Oxytocinergic neurons of the paraventricular nucleus (PVN) of the hypothalamus have been implicated in modulating male sexual responses in rats. Previous investigators have shown that cerebrospinal fluid concentrations of oxytocin (OT) increased after ejaculation and that intraventricular administration of OT and electrolytic lesions of the PVN increased temporal measures of male sexual behavior. Recently, we have demonstrated that OT-immunoreactive neurons in the parvocellular subnuclei of the PVN project to lower levels of spinal cord. In the present study, N-methyl-D-aspartic acid lesions, which have been shown to destroy parvocellular PVN neurons while leaving magnocellular neurons intact, were used to evaluate the role of parvocellular neurons on male copulatory behavior and seminal emissions. OT-immunoreactive fibers were reduced in the lower lumbar spinal cord (L5-L6) following N-methyl-D-aspartic acid lesions in the PVN. This reduction was associated with a significant decrease in seminal emission at the time of ejaculation, but mount, intromission and ejaculatory latencies were unaffected.

Aging↗

Ultrasonic vocalizations during sex behavior of male house mice (Mus musculus): a description.

After placing a female house mouse into the home cage of a male, the occurrences of four behaviors were recorded on separate channels of an event recorder: (1) male sniffing female, (2) male mounting female, (3) male intromitting female, and (4) 70-kHz vocalizations. The amount of vocalizing was greatest shortly after pairing and was associated with the male sniffing the female. After the male began mounting, vocalizations also were associated with mounting. Vocalizations were recorded during intromissions and occasionally occurred coincident with pelvic thrusts. Very few vocalizations were detected when the male was not sniffing or mounting the female. Vocalizations ceased following ejaculation but typically resumed several minutes before the resumption of another mounting sequence. Thus 70-kHz vocalizations appear to be closely linked to male sexual arousal.

Animals↗

Effects of volatile and nonvolatile chemical signals on male sex behaviors mediated by the main and accessory olfactory systems.

Estrous hamster vaginal discharge (HVD) contains both volatile and nonvolatile chemical signals which collectively elicit both male attraction to females and male mating behavior. These two aspects of normal sexual behavior are differentially affected by lesions involving afferents of the main and the accessory olfactory systems. The results of lesions that involve the main olfactory system suggest that it provides information primarily concerning those volatile components of HVD that normally signal the presence of a female. Lesions restricted to the accessory olfactory system do not impair a male's interest in or relative preference for HVD but do significantly interfere with subsequent stages of sexual behavior by reducing the amount of mating obtained upon exposure to HVD. Stimulation of the accessory olfactory system by nonvolatile components of HVD has thus been implicated in the production of mating behavior. In these experiments, male hamsters were attracted to female odor and engaged in significant amounts of mating behavior with surrogate females when only the volatile components of HVD were available to them. These behaviors were further enhanced when both volatile and nonvolatile components of HVD were provided. Lesion studies of the afferents involved reinforce the hypothesis that the main olfactory system is preferentially involved with processing those volatile chemical signals in HVD that denote female attractiveness whereas the accessory olfactory system is preferentially involved with processing those chemical signals, both volatile and nonvolatile, that evoke subsequent steps in male sexual behavior.

Animals↗

[Sex behavior in puberty].

The increasing number of Aids cases raises questions as to the risks to which young people are exposed. The present study attempts to illustrate the psychological development of sexuality during puberty. Taking development-psychological and depth-psychological aspects into account, the author attempts to throw light on the development of the ego and the instinctual and defensive behavior of young people. These intrapsychic constellations and social norms have a major influence on young people's sexual behavior.

Adolescent↗

[Sex behavior following primary radiotherapy of cervix cancer].

57 women with invasive cervical carcinoma treated by primary irradiation were asked by means of a questionnaire about their partnership, especially about their sexual life. 9 women (15.7%) had no more sexual intercourse. 50% of those 48 patients who were sexually active also after the treatment had marked discomfort during coitus due to lack of lubrication. They reported pain caused by a short or narrow vagina less often (20.8%). Only 33.3% had their first intercourse 3 months after the irradiation, frequency of cohabitation was reduced in 68.4% of the patients. The reason for this was fear of recurrence of the cancer, fear of pain and lack of libido: 57.9% of the women mentioned reduced libido. Before irradiation 14% had no orgasm during the coitus, but 52% had none after treatment. The sexual life was not disturbed in those women who had been well informed about the consequences of the irradiation and who had their first intercourse soon after the therapy.

Adult↗

Reduction of lipocalin-type prostaglandin D synthase in the preoptic area of female mice mimics estradiol effects on arousal and sex behavior.

In female rodents, sleep and activity levels fluctuate over the estrous cycle. When estradiol (E2) levels are highest, sleep is reduced whereas locomotion is increased. The preoptic area (POA) is a key site for estrogenic regulation of these functions. However, molecular mechanisms by which E2 acts to reduce sleep and increase activity are unclear. Recently, we demonstrated a twofold reduction in lipocalin-type prostaglandin D synthase (L-PGDS) transcript levels, after E2 treatment, in the ventrolateral POA (VLPO), a putative sleep-active nucleus. Catalytic activity of L-PGDS produces PGD2, an endogenous somnogen. Thus, we hypothesized that decreases in PGD2 in the VLPO may contribute to the generalized arousal mediated by estrogens. To test this, we infused (i) antisense oligonucleotides (oligos), containing locked nucleic acid moieties (an improved technology), targeted to L-PGDS mRNA, (ii) scrambled sequence control oligos, or (iii) saline vehicle into the VLPO of ovariectomized female mice treated with E2 or oil. Arousal states and activity levels were assessed in response to a series of sensory stimuli (vestibular, olfactory, and somatosensory). The vestibular stimulus, which was administered first, resulted in the strongest responses and elicited significantly different responses among the groups: all groups in the E2 cohort demonstrated increases in overall home cage activity and duration of that activity compared with the oil-treated control groups. As predicted from E2 suppression of L-PGDS transcript levels, the responses of the locked nucleic acid antisense oligo-treated animals from the oil cohort did not differ from the E2-treated groups, such that they also demonstrated increases in activity and duration of activity compared with their controls. Thus, reducing L-PGDS in the VLPO of oil-treated females mimicked the effect of E2 on activity and arousal and represents a unique molecular pathway through which E2 may modulate these functions.

Animals↗