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PubMed2003

Changes in androgen receptor mRNA expression in the forebrain and oviduct during the reproductive cycle of female leopard geckos, Eublepharis macularius.

Successful reproduction requires the coordination of reproductive physiology with behavior. The neural correlates of reproductive behavior have been elucidated in a variety of amphibians, mammals, and birds but relatively few studies have examined reptiles. Here we investigate differences in androgen receptor (AR) mRNA expression in the forebrain and oviduct between previtellogenic and late vitellogenic female leopard geckos, Eublepharis macularius. Plasma concentrations of testosterone (T) are low when females are previtellogenic and sexually unreceptive but increase dramatically during late vitellogenesis when females are receptive. In addition, receptivity can be induced by treatment with exogenous T. The relative abundance of AR-mRNA across various nuclei was greater in late vitellogenic than in previtellogenic females. This general pattern was observed in the medial preoptic area, anterior hypothalamus, external nucleus of the amygdala, dorsolateral aspect of the ventromedial hypothalamus, lateral septum, and periventricular hypothalamus. There were also clear differences in AR-mRNA expression among these nuclei. The pattern of gene expression observed in the brain was reversed within stromal cells of the oviduct where expression of AR-mRNA decreased from the previtellogenic stage to the late vitellogenic stage. Overall, these data demonstrate that T concentration in the plasma, abundance of AR-mRNA in the brain and oviduct, and sexual behavior change coordinately during the reproductive cycle of female leopard geckos. Although the function of AR in the female leopard gecko is not yet clear, our results are in accord with growing evidence that androgens regulate numerous aspects of female physiology and behavior in vertebrates.

Animals↗
PubMed1991

Effects of non-competitive NMDA receptor antagonists on reproductive and motor behaviors in female rats.

MK-801 and dextrorphan, selective non-competitive antagonists at N-methyl-D-aspartate (NMDA) receptors, were used to evaluate the effect of NMDA receptor blockade on sexual and motor behaviors in female rats. Ovariectomized rats were treated with estradiol benzoate (EB) for 48 or 72 h followed by progesterone (P) 3.5-4 h before testing the animals for sexual receptivity. After testing for estrous responsiveness, the effect of NMDA antagonists on several motor behaviors was also assessed. Lordosis frequency and intensity were inhibited in animals that received 0.5 mg/kg MK-801 30 min before EB; the same dose of MK-801 was relatively ineffective when administered 24 h after EB. In neither case did MK-801-treated females differ from controls when motor behaviors were assessed after mating tests. When 30 mg/kg dextrorphan, a short-acting NMDA antagonist, was administered 15 min before P, sexual behavior was not blocked. However, both 0.05 mg/kg MK-801 and 30 mg/kg dextrorphan suppressed ongoing female sexual behavior within 30 min in animals made receptive with EB and P. These deficits in sexual behavior were associated with changes in motor performance. MK-801 (0.1 mg/kg) and dextrorphan (30 mg/kg) abolished movement in the vertical dimension (e.g. jumping and rearing). By contrast, the drugs increased movement in the longitudinal (locomotion) and lateral (circling) dimensions. At 0.2 mg/kg, MK-801 blocked movement in both the vertical and longitudinal dimensions; however, it failed to block circling. Only at 0.4 mg/kg did MK-801 inhibit lateral movements and righting reflexes.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Effects of intracranial implants of dihydrotestosterone on the reproductive physiology and behavior of male guinea pigs.

An experiment was conducted to determine whether the intracranial application of dihydrotestosterone (DHT), a nonaromatizable androgen, would stimulate male guinea pig mating. Of three castrate groups studied, one was a control group in which subjects were implanted both in the medial preoptic area (MPOA) and under the skin with cannulae containing cholesterol (NoDHT). Males in one of the experimental groups received implants of cholesterol in the MPOA plus subcutaneous implants containing DHT (ScDHT). Members of the other experimental group were subcutaneously implanted with cholesterol and simultaneously given intracranial implants of DHT (IcDHT). Compared to either the NoDHT control group of the ScDHT experimental group, greater numbers of males in the IcDHT group displayed mounts (P less than 0.01), intromissions (P less than 0.01), and ejaculations (P less than 0.001). Additionally, the hypothalamic implants of DHT had no significant effects on peripheral target tissues. These data indicate that androgenic stimulation of the guinea pig brain is sufficient to activate masculine sexual behavior in this species.

Animals↗
PubMed1985

Reproductive physiology and behavior in the male rat following acute and chronic peripheral adrenergic depletion by guanethidine.

The effect of guanethidine, an adrenergic neuron blocking agent, on sexual behavior, penile reflexes, and spontaneous seminal emission (SSE) in the rat was studied by acute (i.e., 4 hours prior to testing) and daily IP injection of a low (5 mg/kg) and moderately high (25 mg/kg) dose of the drug. Acute low dose treatment eliminated the expulsion of a seminal plug with behavioral ejaculation without affecting sexual behavior; while acute high dose administration significantly decreased the number of intromissions preceding ejaculation and eliminated emission in copula and SSE for 3 days, with no evidence of retrograde ejaculation. Acute high dose treatment also increased the number of long flips displayed in the penile reflex test, and resulted in significant depression in plasma testosterone (T) and luteinizing hormone (LH) levels. Daily injection with the low dose eliminated emission in and ex copula for 4 weeks, without altering sexual behavior or penile reflexes. Seminal emission in copula reappeared more rapidly after stopping injections than SSE. Chronic high dose treatment was also without effect on copulatory activity. There was a partial recovery of emission in copula by the fourth week of treatment, suggesting that a nonadrenergic mechanism had assumed this function. In penile reflex tests conducted after 4 and 8 weeks, significantly fewer erections were displayed by drug-treated animals. During the period of initial recovery of emission in copula, emission during the reflex test was markedly increased, but SSE was decreased. Plasma T was significantly suppressed after two and four weeks of daily injections, but not thereafter, while plasma LH levels were not affected by the drug.

Animals↗
PubMed2004

Long-term effects of pubertal anabolic-androgenic steroid exposure on reproductive and aggressive behaviors in male rats.

The current study examined acute and long-term effects of anabolic-androgenic steroid (AAS) exposure during puberty on copulation, vocalizations, scent marking, and intermale aggression, both with and without tail pinch, in intact male rats. Animals received 5 mg/kg of testosterone, nandrolone, stanozolol, or vehicle, beginning at puberty. After 5 weeks, behavior tests were performed while continuing AAS injections. AAS treatment was then discontinued. Behaviors were tested during 3-5 weeks, 9-11 weeks, and 15-17 weeks of withdrawal. During AAS administration, stanozolol males showed significant reductions in all behaviors compared with controls, except aggression with tail pinch. Nandrolone treatment significantly reduced vocalizations and scent marking, and testosterone had no significant effect on behavior. During withdrawal, behaviors in stanozolol males recovered to control levels at variable rates: aggression at 4 weeks; mounts, vocalizations, and scent marking at 9 weeks; and ejaculations at 15 weeks of withdrawal. Stanozolol males showed significantly higher levels of tail pinch-induced aggression during every withdrawal test. Nandrolone-treated males scent-marked at control levels by 9 weeks withdrawal but displayed significantly fewer vocalizations and significantly more tail pinch-induced aggression than controls for the entire study. Testosterone-treated males scent-marked significantly below controls at 3 weeks withdrawal and showed significantly more tail pinch-induced aggression at 5 weeks withdrawal. All three AAS significantly increased tail pinch-induced aggression compared with corresponding nontail pinch tests, even at study endpoint. These results suggest that alterations in androgen-dependent behaviors by pubertal AAS exposure can persist long after drug exposure, and some effects may even be permanent.

Aggression↗
PubMed2003

Effects of pubertal anabolic-androgenic steroid (AAS) administration on reproductive and aggressive behaviors in male rats.

Adolescence in human males is a hormonally sensitive period when many adult behaviors develop, including sexual and aggressive behaviors. Using a rat model, the authors examined the effects of three anabolic-androgenic steroids (AAS) during puberty: testosterone, nandrolone, and stanozolol. Copulation, vocalizations, scent-marking, and aggression were tested following AAS exposure. Relative to gonadally intact controls, rats injected with testosterone showed a significant increase in scent-marking and aggression in the opponent's home cage. Nandrolone had no effect. Stanozolol significantly inhibited all behaviors. Results suggest that depending on the chemical structure of the steroid, AAS exposure during puberty affects several androgen-dependent behaviors. Because adolescence in humans is a period of hormonal change, abuse of AAS, particularly stanozolol, during this time may disrupt the establishment of normal adult behavior patterns.

Age Factors↗
PubMed2000

Correlation between an early sexual debut, and reproductive health and behavioral factors: a multinational European study.

OBJECTIVE: To investigate whether women who made an early sexual debut differ from those with a later debut regarding genital signs and symptoms. METHODS: The study included women who considered themselves gynecologically healthy and who attended 17 family planning centers in 13 European countries for contraceptive advice. There were 629 women who made their sexual debut at the age of 16 years or earlier (study population) and 927 women who had their first sexual intercourse at the age of 19 years or later (comparison group). Genital symptoms and signs, contraceptive use, smoking, and genital hygiene habits and previous genital infections were recorded on a structured patient record form. Detection of Chlamydia trachomatis was made by means of a polymerase chain reaction on first-void urine. The study was made, on average, 7-10 years after the women's sexual debut. RESULTS: The mean age of first intercourse was 15.3 years for the study group versus 20.7 years for the control group (p < 0.001). The study population had significantly more symptoms, such as vaginal discharge and pruritus, and signs, such as abnormal discharge, erythema of the vaginal mucosa and lower genital tract infections, than the comparison group. Twice as many women in the study group were smokers and there was a ten-fold increase among these subjects of using low-pH solutions for genital hygiene. The prevalence of C. trachomatis infection did not differ between the two groups (p = 0.22). CONCLUSION: Age at first intercourse is not only a predictor of sexual risk behavior, but also a predictor, regarding both signs and symptoms, of future gynecological problems.

Adolescent↗
PubMedDate not supplied

The estrogenic and antiandrogenic pesticide methoxychlor alters the reproductive tract and behavior without affecting pituitary size or LH and prolactin secretion in male rats.

This study was designed to determine if long-term exposure to high doses of methoxychlor (M) would alter pituitary or testicular endocrine functions in either an estrogenic or antiandrogenic manner. Weanling male Long-Evans hooded rats were dosed daily with M (po) at 0, 200, 300, or 400 mg kg-1 day-1 for 10 months. Methoxychlor treatment delayed puberty by as much as 10 weeks and reduced fertility and copulatory plug formation in a dose-related manner at the initial mating. During mating, M-treated males exhibited shorter latencies to mount and ejaculate versus control males, but the number of intromissions prior to ejaculation was unaffected, indicating that M enhanced the arousal level in the males in an estrogen-dependent manner. Most treated males eventually mated but time-to-pregnancy was lengthened. Very low sperm counts were associated with infertility, while prolonged delays in puberty reduced fecundity. Methoxychlor treatment with 200 to 400 mg kg-1 day-1 failed to mimic the chronic effects of a sustained (8 months) low dose of estradiol-17 beta (3-mm silastic implants) on pituitary or testicular hormone levels. Estradiol administration increased pituitary weight 4-fold, serum levels of luteinizing hormone (LH) were reduced by almost 50%, and serum prolactin was increased 40-fold, while M did not affect any of these measures. These data demonstrate that M affects the CNS, epididymal sperm numbers, and the accessory sex glands and delays mating without significantly affecting the secretion of LH, prolactin, or testosterone. These data indicate that M did not alter pituitary endocrine function in either an estrogenic or antiandrogenic manner. To our knowledge, these data provide the first in vivo example of such a pronounced degree of target tissue selectivity to an environmental endocrine-disrupting chemical.

Animals↗
PubMed1988

Effects of photoperiod and filtered light on growth, reproduction, and mating behavior of turkeys. 1. Growth performance of two lines of males and females.

This study was designed to determine the effects of photoperiod and filtered light on growth of male and female turkeys. Large White (LW) and Medium White (MW) turkeys were reared under intermittent (2 h light: 2 h dark) or diurnal (12 h light: 12 h dark) photoperiods using white light, red (650 nm), or blue (450 nm)-filtered lights. Both males and females grew more rapidly under blue light than under red or white light up to 16 wk of age. After that age, rates of gain were significantly better under the white and red lights. Growth rates were significantly greater under the intermittent than under the diurnal photoperiod for both lines and sexes in Experiment 1 but not in Experiment 2. The greatest acceleration in growth rate was observed from 4 to 10 wk of age, with this advantage still evident at 24 wk of age. No significant differences in feed efficiency due to photoperiod or light color occurred. Early mortality was highest under blue light but late mortality was greater under red and white light. Mortality was higher for the LW than MW birds. Live grades were unaffected by light regimen or light color, but feather condition was poorest for birds reared under the white diurnal photoperiod.

Animals↗
PubMedDate not supplied

[Progesterone and its metabolites in central nervous system function].

Progesterone (P4) and its metabolites are involved in several functions of the central nervous system (CNS). These steroids participate in neuronal excitability, reproduction and sexual behavior. P4 and its metabolites exert their effects on neurons and glial cells through several mechanisms that include the interaction of the steroids with: 1) intracellular specific receptors; 2) modulatory sites located in neurotransmitter receptors; and 3) ionic channels. By these mechanisms, modifications in gene expression, second messengers' production and ion conductance are induced. The activities of the P4 metabolites have been mainly related to membrane effects, whereas for P4, the transcriptional and translational effects are mediated by intracellular receptors. Thus, these steroids can modify the CNS functions at short (milliseconds), medium (minutes) or long term (hours or days) lapses. The knowledge of the molecular mechanisms involved in the actions of P4 and its metabolites in the CNS will contribute to the understanding of fundamental biological processes such as sexual behavior and reproduction, and it will open the possibility of alternative therapies in the treatment of some neurologic and psychiatric disorders such as epilepsy, anxiety, premenstrual syndrome, and cerebral tumors which possess hormonal regulation.

Animals↗
PubMed2002

Androgens and environmental antiandrogens affect reproductive development and play behavior in the Sprague-Dawley rat.

In mammals, exposure to androgens early in development is essential for masculinization of the male reproductive phenotype. Male fetuses exposed to antiandrogens during perinatal life are permanently demasculinized in their morphology and physiology, whereas exposure to exogenous androgens permanently masculinizes females. In some litter-bearing species, proximity(italic) in utero(/italic) of females to males can partially masculinize female siblings and alter their responsiveness to endocrine-disrupting compounds. However, in our strain of rat (CD-SD Charles River), intrauterine position does not significantly influence testosterone concentrations and anogenital distance of fetuses. In comparison, administration of testosterone propionate to pregnant females, at doses that doubled fetal female testosterone levels, did masculinize the reproductive system. Discovery of androgen-active chemicals in the environment has placed increased emphasis on describing the reproductive and behavioral effects of both natural and environmental androgens and antiandrogens. Recently, the effects of an antiandrogen, vinclozolin, on the brain and behavior were cited as a special concern by the U.S. Environmental Protection Agency in its risk assessment of this pesticide. In rats, one such behavior that is perinatally organized by androgens is social play. Males play more than females, and administration of exogenous androgens during the neonatal period alters the juvenile expression of this sexually dimorphic behavior. Vinclozolin is an androgen receptor antagonist that inhibits androgen-dependent tissue growth in vivo. We were interested in whether developmental exposure to vinclozolin could also alter androgen-dependent behaviors such as play. Neonatal male rats were injected on postnatal days (PNDs) 2 and 3 with corn oil, the pharmacologic antiandrogen flutamide (50 mg/kg), or vinclozolin (200 mg/kg). On PNDs 36-37 animals were observed for social play. Behaviors associated with general social activity such as sniffing and dorsal contact were unaffected by treatment. However, play behavior in males treated with flutamide or vinclozolin was significantly reduced, resembling levels of play characteristic of females rather than untreated males. Therefore, this study demonstrates that perinatal exposure to vinclozolin, an environmental antiandrogen, can alter androgen-dependent play behavior in the male rat.

Androgen Antagonists↗