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PubMed1982

Development of feminine sexual behavior in the rat: androgenic and temporal influences.

The contributions of prenatal and postnatal androgen exposure upon the development of sexual behavior in rats were examined by prenatal treatment of pups with an androgen antagonist (flutamide) and postnatal androgenization or castration. Male and female rats were exposed to the androgen receptor-blocker flutamide (FLU) in utero via prenatal injections to the mother on Days 10 through 22 of gestation. At birth (Day 1) males were castrated. Both males and females were injected with either 100 micrograms testosterone propionate (TP) or oil on Day 1. In adulthood all gonadectomized animals were tested for the display of feminine sexual behavior (lordosis) in response to a range of estrogen dosages. Prenatal exposure to FLU enhanced lordosis in both sexes when compared to vehicle-treated controls. Postnatal TP treatment decreased lordotic potential as expected. However, in animals given TP postnatally, those receiving prenatal flutamide had higher lordosis quotients than animals receiving vehicle treatment. These data confirm (1) that the development of feminine sexual behavior is inhibited by androgen exposure, (2) that such exposure occurs prenatally, (3) that the potential for feminine behavioral differentiation occurs prenatally as well as postnatally, and (4) that androgen acts perinatally to affect estrogen sensitivity in adulthood.

Aging↗
PubMed1982

Neonatal decortication and adult female sexual behavior.

Neonatal lesions of the cerebral cortex in female rats did not eliminate female sexual behavior as measured by lordosis. However, lordosis in response to prolonged low levels of estradiol benzoate (1.0 micrograms/day for 6 days) was attenuated in lesioned females. Following estradiol benzoate plus progesterone (0.5 mg) treatment the probability of lordosis increased markedly in the decorticate females, but still remained below control levels. Decorticate females were mounted by the male at least as often as control females. Hopping and darting and rejection behaviors on the part of the female were virtually eliminated in the decorticate group. However, these females continued to direct sniffing behavior toward the male at levels above those of the controls.

Animals↗
PubMed1983

Progesterone-induced sequential inhibition of copulatory behavior in hysterectomized rats: relationship to neural cytoplasmic progestin receptors.

The inhibitory effects of progesterone on the copulatory behavior and on neural cytoplasmic progestin receptors were examined in ovariectomized (DV) and ovariectomized-hysterectomized (OH) rats. Ovariectomized and OH rats were given 2.0 micrograms of estradiol benzoate (EB) followed 24 hr later by 0.1, 0.5, 0.1 or 2.0 mg of progesterone (P) and were tested for lordosis 6 hr later (30 hr). Twenty four hr after the first P treatment, all animals received 0.5 mg of P and were tested again (54 hr). The initial doses of 1.0 and 2.0 mg of P significantly reduced lordosis quotients in response to the subsequent P treatment in OV animals but only the 2.0 mg dose of P effectively suppressed lordosis in OH animals. In order to determine whether the priming dose of EB influences the inhibitory effects of progesterone, OV and OH rats were injected with 1.0 microgram of EB followed by 1.0 mg of P, or 6.0 micrograms of EB followed by 2.0 mg of P and were tested for receptivity under the same schedule. Treatment with 1.0 microgram of EB permitted, and 6.0 micrograms of EB prevented sequential inhibition of sexual behavior by progesterone in both OV and OH rats. Hypothalamic cytoplasmic progestin [( 3H]R5020) receptors were then measured 48 hr after EB injection in OV or OH rats given the same treatments with EB and P. Hypothalamic progestin receptors were significantly lower in OV animals given 2.0 micrograms of EB followed by 1.0 or 2.0 mg of P than oil-treated controls, but only the 2.0 mg dose of P significantly reduced receptors in OH rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1983

Effects of an anti-androgen and 5 alpha-reductase inhibitors on estrus duration in the cycling female rat.

Five experiments examined the role of circulating androgens in the control of sexual behavior (lordosis) in the intact cycling rat. The androgen receptor blocker, flutamide (FLU), was administered daily to cycling rats beginning on the day of estrus, and lordotic responsiveness was measured on the 2nd subsequent proestrus day and on the day of estrus. FLU-treated females showed significantly higher levels of lordosis throughout the end of the period of estrus than controls (Experiment 1). Neither the maximal levels of lordosis seen on the evening of proestrus nor the time of onset of estrous responsiveness during the preceeding afternoon were affected by FLU (Experiment 2). Serum estradiol concentrations seen on the morning of proestrus (Experiment 3) did not differ between FLU- and vehicle-treated animals. The weak 5 alpha-reductase inhibitor, testosterone-17 beta-carboxylic acid (17 beta C), prolonged slightly, but did not significantly lengthen, the period of estrus (Experiment 4), while the highly potent steroidal 5 alpha-reductase inhibitor, 4 MA, significantly increased the rate at which estrous behavior declined on the day of estrus (Experiment 5). Circulating androgens do not appear to affect the maximal level of sexual receptivity displayed nor the time of estrus onset; however, they may govern the duration of the period of estrus by influencing the rate of estrus termination.

Anilides↗
PubMed1984

Effects of progesterone on lordotic responses to specific mating stimuli in hamsters.

Mating-induced inhibition of sexual receptivity was examined in ovariectomized, estrogen (E) treated and estrogen plus progesterone (E + P) treated hamsters given 10 min of exposure to male mounting stimulation alone or to mounts, intromissions, and ejaculations at eight hourly intervals. In E + P treated females, no differential effects of exposure to full mating stimulation vs. mounting stimulation alone were observed. In contrast, females given E treatment alone showed a marked differential response. Fully mated, E-treated females showed more lordosis than E-treated females exposed to mounts alone during the initial test. However, total lordosis duration declined precipitiously in the fully mated group by 2 hr and remained significantly below that in other groups during subsequent tests. Levels of receptivity in E-treated females mounted-only remained relatively constant until 8 hr. These results suggest that P reduces the inhibitory effects of vaginocervical cues received during mating without affecting the response to mounting stimulation alone. In addition, vaginocervical stimulation may initially facilitate lordosis in E-treated females.

Animals↗
PubMed1984

Olfactory cues from the female can affect feminine behavior in the male rat.

The aim of this work was to study the influence of the hormonal milieu on the facilitory effects of olfactory stimuli originating from female urine on lordosis behavior in orchidectomized (ORCH) feminized rats. Urine from ovariectomized (OVX) rats was shown to increase the proportion of ORCH rats displaying lordosis behavior, an effect which was enhanced if the OVX rats had been given progesterone. Treatment of OVX rats with estradiol benzoate did not affect the pheromonal activity of their urine. Dexamethasone treatment of OVX rats completely suppressed the facilitory effects of their urine on the feminine behavior in males. A higher proportion of feminized rats displayed lordosis following exposure to urine collected from pseudopregnant rats than did their unexposed counterparts. Dexamethasone treatment of pseudopregnant rats did not abolish this effect. These results suggest that the adrenal cortex is capable, in the absence of the ovaries, of manufacturing some pheromonal substance which stimulates feminine behavior in the male rat. The nature of this substance remains unknown. Furthermore progesterone itself is involved in the emission of olfactory signals which control feminine behavior in the male rat.

Androstenedione↗
PubMed1985

The role of mesencephalic tegmentum in regulating female rat sexual behaviors.

Feminine sexual behaviors were tested in estradiol benzoate (EB) and progesterone (P) primed ovariectomized rats following four types of radiofrequency lesions in the midbrain tegmentum. The dorsomedial lesion (DML) which destroyed the ventromedial central gray including the dorsal raphe nucleus and adjacent area induced high sexual receptivity in the females primed with low dose (0.5 micrograms) of EB-P. All females with DML exhibited lordosis and ear wiggling, the mean lordosis quotient (LQ) being significantly higher than that of castrated controls or sham operated rats. Sexual receptivity in females with ventromedial tegmental lesion was not significantly different from those of the control and sham groups. In contrast to the medially lesioned groups, the mean LQ was low in the animals with bilateral lateral tegmental lesions even when the dose of EB was increased to 2 micrograms which was sufficient to induce high sexual receptivity in castrated and sham operated control females. In the animals with dorsolateral tegmental lesions (DLL), a much more severe loss of lordosis was seen than in those with ventrolateral tegmental lesions (VLL). None of the DLL females displayed sexual behavior throughout the present experiments. These results lead us to conclude that the midbrain dorsomedial tegmental area (ventral central gray and the adjacent area) is concerned with female sexual behavior inhibiting system, whereas the lateral tegmental area may be involved in the facilitatory system.

Animals↗
PubMed1988

Dual progesterone action in diencephalon facilitates the induction of sexual receptivity in estrogen-primed golden hamsters.

In order to identify and characterize the progesterone (P) sensitive neural system that regulates feminine sexual behavior, 28-gauge P-filled cannulae were implanted in the medial preoptic area (MPO), ventromedial hypothalamus (VMH), and central gray (CG) of ovariectomized estrogen-primed golden hamsters. Dual implants of P were placed either ipsilaterally or contralaterally in brain sites consisting of MPO-VMH, MPO-CG, or VMH-CG combinations. Tests for sexual receptivity commenced 44 hr after estrogen priming and consisted of a preimplantation test followed 4.5 to 5.5 hr later by a postimplantation test. In the preimplantation test, stimulus males were attacked when placed into the female's home cage which indicated that the subsequent display of sexual receptivity occurring in the postimplantation test was due to the action of P. Dual implants of P placed either ipsilaterally or contralaterally in MPO-VMH regions were significantly more effective in facilitating lordosis behavior than dual P implants placed in MPO-CG or VMH-CG regions. However, the duration of lordotic responsiveness produced by dual P implants in MPO and VMH regions appears to be shorter than the duration of lordosis typically observed in intact females on proestrus. Results suggest that MPO and VMH regions are sensitive to the lordosis facilitating actions of small dual implants of P.

Animals↗
PubMed1988

Cholinergic mechanisms of lordotic behavior in rats.

Cholinergic mechanisms of lordotic behavior were studied in hooded rats using behavioral techniques and autoradiographic analysis of the diffusion of [3H]N methyl scopolamine ([3H]NMS) applied to the hypothalamus. Bilateral cannulae were implanted chronically in the region of the ventromedial nuclei (VMN). A series of cholinergic drugs and estradiol (E2) were administered to each rat during successively induced periods of estrus. Robust inhibition of lordosis resulted from administration of atropine and scopolamine. Robust facilitation followed carbachol administration. Pirenzepine, hexamethonium, and tetraethylammonium did not inhibit lordosis. [3H]NMS, the last drug in the series to be administered, inhibited lordosis in two of three rats. Autoradiographic analysis of [3H]NMS diffusion in these rats revealed that radioactivity was confined entirely to the hypothalamus and appeared in the region of the VMN. In an additional experiment, the in vitro binding characteristics of [3H]NMS in the basomedial hypothalamus were examined. The VMN appeared lightly labeled and were surrounded by regions of darker labeling. We conclude that cholinergic drugs influence lordotic behavior when applied in crystalline form in the vicinity of the VMN of the female rat hypothalamus.

Acetylcholine↗
PubMed1988

Abolition of vagino-cervical stimulation-induced analgesia by capsaicin administered to neonatal, but not adult rats.

We have previously reported that vagino-cervical mechanical stimulation (VS or probing) produces analgesia in rats. Neonatal treatment with capsaicin (CAP) has been shown to reduce the concentrations of several neuropeptides in dorsal root ganglia, spinal cord, and autonomic ganglia, via a neurotoxic effect. In the present study, we report that CAP administered in the neonatal period abolishes the analgesic effect of probing in adulthood. In addition, we report that the ability of VS to potentiate the lordosis response to manual stimulation of the flanks is abolished by neonatal CAP treatment. By contrast, rats treated as adults with CAP show the typical VS-produced effects of analgesia and potentiation of the lordosis response. Our results suggest that neonatal, but not adult, CAP treatment depletes a neuropeptide(s) that mediates the analgesia and lordosis-inducing effects of VS.

Age Factors↗
PubMed1988

A comparison of the effects of three androgens on sexual differentiation in female hamsters.

The effectiveness of the synthetic androgen 17 beta-hydroxy-17 alpha-methyl-estra-4,9,11-triene-3-one (R 1881), 5 alpha-dihydrotestosterone (DHT), and testosterone to suppress the development of lordotic behavior in female hamsters were compared. Selection of these three androgens was based upon their ability to identify the active agent in defeminization. While all three hormones bind with high affinity to CNS androgen receptors, R 1881 differs from DHT because it is presumably not metabolized into less potent androgens and differs from testosterone because it is presumably not metabolized into estrogen. At birth, female hamsters were given either a single injection of 100 micrograms of hormone, five daily injections of 100 micrograms of hormone, or implanted with Silicone elastomer capsules containing hormone. Controls consisted of hamsters receiving oil injections or cholesterol implants. As adults, the hamsters wee gonadectomized, injected with estradiol benzoate and progesterone and then tested for lordosis. A single injection of androgen at birth was ineffective in suppressing lordosis duration in female hamsters. Multiple injections and implants of R 1881 or testosterone inhibited the development of female sexual behavior. R 1881 administered as five daily injections or implanted for seven days caused a similar partial reduction in lordosis duration. Testosterone was more effective in inhibiting receptivity when given as implants rather than injection. No differences were observed between females receiving testosterone implants at birth and males. DHT had no appreciable effect upon the development of behavior regardless of the route of administration or the length of treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Cholinergic regulation of female sexual behavior in rats demonstrated by manipulation of endogenous acetylcholine.

Infusions of the cholinesterase inhibitor, eserine, into the lateral ventricle of the brain facilitated lordosis in ovariectomized, estrogen primed female rats. Lordosis was also facilitated by infusions of 5 or 10 micrograms acetylcholine when this was accompanied by a low dose of eserine. Systemic treatment with the muscarinic antagonist, atropine (2 mg), completely blocked the facilitative effects of eserine and acetylcholine. In female rats made highly receptive by treatment with estrogen and progesterone, lordosis was inhibited by infusion of scopolamine into the lateral ventricles. These results agree with previous findings that sexual receptivity is regulated in part by endogenous cholinergic activity.

Acetylcholine↗
PubMed1990

Cholinergic regulation of sexual behavior in female hamsters.

The effect of cholinergic manipulations on sexual behavior in female hamsters was determined in a series of experiments. The cholinergic receptor antagonist, scopolamine, reduced total lordosis duration following systemic (1 mg/kg) or intraventricular (10 and 20 micrograms bilaterally) administration to ovariectomized hamsters primed with estrogen and progesterone. The inhibitory effect of scopolamine on lordosis occurred within 15 min after either treatment route and persisted at 2 hr after systemic administration. Intraventricular administration of the acetylcholinesterase inhibitor, physostigmine (10 micrograms bilaterally), activated lordosis of short duration in ovariectomized hamsters primed only with estrogen. These results indicate that the cholinergic system plays a facilitative role in the regulation of sexual behavior in female hamsters similar to that demonstrated previously in female rats. The activational effect of cholinergic neurotransmission on female sexual behavior may be a neural mechanism common to a number of mammalian species.

Animals↗
PubMed1991

The effects of short day exposure on seasonal and circadian reproductive rhythms of female golden hamsters.

Four groups of female golden hamsters were exposed to short photoperiods (SP, LD 10:14) for 4, 14, 20, or 27 weeks and tested for physiological markers (uterine weight and estrous cycles) and behavioral (lordosis, approach and aggressive behaviors) measures while in contact with a stud male. After behavioral testing, females were ovariectomized and, during the next 2 weeks, were tested twice more (with a stud male) after replacement with 0.33 microgram (low dose) and 1.0 microgram (high dose) EB plus progesterone (500 micrograms). Results show that, after 14 weeks of SP conditions, uterine weights and percentage of females showing normal estrous cycles are at a minimum. This is mirrored by minimal levels of lordosis and maximal levels of aggressive and approach behavior at week 14. Physiological measures did not fully recover (to preregression levels) until week 27; however, behavioral measures show an earlier recovery by week 20. SP exposure also affects the circadian patterning of behaviors: Females that show lordosis at week 14 did so later in the day than did females tested at other weeks. Females in the regressed state also fail to show a significant decrease in approach behaviors (and a significant increase in receptive behaviors) over the course of the circadian day, a pattern seen in nonregressed females. Following hormone replacement with the low EB (+P) dose, females do not become receptive; however, at the higher dose, all but the week 14 group show increased receptivity.(ABSTRACT TRUNCATED AT 250 WORDS)

Aggression↗
PubMed1991

Effects of prenatal antiandrogen treatment on masculinization and defeminization of guinea pigs.

Gonadectomized (gdx) guinea pigs which had received the antiandrogen flutamide prenatally were tested for female-typical and male-typical sexual behavior in adulthood. In tests for lordosis behavior, gdx males and females were injected with estradiol benzoate and progesterone. Prenatally flutamide-treated females showed a longer mean lordosis response than control females. This was true whether they were given either a high or a low dose of EB. No male ever showed a lordosis response. In tests for male-typical sexual behavior, gdx adult males were treated with testosterone propionate and tested with stimulus females. The prenatally flutamide-treated males showed significantly decreased levels of ejaculation, a lower intromission rate and a decreased percentage of mounts which included pelvic thrusts, when compared to control males. Mount rate and rate of pericopulatory behavior did not differ between the flutamide and control males. The fact that prenatal administration of flutamide increased female-typical behavior in adult females suggests that the female guinea pig is normally partially defeminized by androgens in utero. The male guinea pig appears to be resilient to attempts to block defeminization with prenatal antiandrogens. However, some aspects of masculinization can be blocked.

Androgen Antagonists↗
PubMed1993

The effect of prenatal stress on adult sexual behavior in rats depends on the nature of the stressor.

It is well known that prenatal stress induces behavioral demasculinization and/or feminization in male offspring during adulthood. In this study, four different stressors were prenatally applied to rats. Pregnant rats were subjected to immobilization, unavoidable electric foot shocks, rapid eye movement sleep deprivation (REMd), or immersion in cold water. During adulthood, male offspring were tested for masculine and feminine sexual behavior. The results corroborated the fact that immobilization induced an impairment of masculine sexual behavior and a facilitation of feminine sexual behavior. Electric shocks showed only minor differences in masculine behavior when compared to intact controls, and no signs of lordosis behavior were observed. The REMd group displayed a major impairment of masculine behavior, even greater than that observed within the immobilization group. However, lordosis behavior was only induced with estradiol. On the other hand, water immersion seems to have a facilitatory effect on several parameters of masculine behavior and did not show lordosis behavior even with hormonal treatment. These results strongly suggest that changes in sex behavior induced by prenatal stress are linked to the nature of the stressor.

Animals↗
PubMed1994

Pelvic neurectomy blocks oxytocin-facilitated sexual receptivity in rats.

The effect of bilateral pelvic, hypogastric, or pudendal neurectomy on oxytocin-induced facilitation of lordosis behavior was examined in ovariectomized, estrogen, and progesterone primed female rats. Oxytocin-induced facilitation of lordosis behavior was significantly decreased following bilateral pelvic, or combined bilateral pelvic and hypogastric neurectomy. Hypogastric only or pudendal only neurectomy had no effect on the facilitation of lordosis behavior after systemic administration of oxytocin. These results suggest that the integrity of the pelvic nerve is necessary and sufficient to mediate the stimulatory effects of systemically administered oxytocin on receptivity.

Afferent Pathways↗
PubMedDate not supplied

Inhibition not facilitation of sexual behavior by PCPA.

It has been proposed that estrous behavior in the female rat may be under tonic inhibition by a central serotonergi system. Studies conbining estrogen priming and the pharmacological depletion of serotonin have provided some support for this hypothesis. Some evidence, however, is not consistent with this hypothesis. In the present study estrogen primed ovariectomized-adrenalectomized rats were administered p-chlorophenylalanine and were tested for lordosis behavior 66 and 70 hr later. Lordosis was not facilitated. The animals were then administered progesterone and retested at hour 74. PCPA inhibited progesterone-induced lordosis behavior in a dose dependent manner.

Adrenal Glands↗