Control Of Sexual Receptivity Research Articles

Raloxifene effects upon the neuronal system controlling sexual receptivity in female rats

Selective estrogen receptor modulators (SERMs) constitute a new family of drugs with growing interest in the management of estrogen-associated pathology. Raloxifene is a SERM that mimics estrogen action on bone and blood lipid concentration but whether it acts as estrogen in the central nervous system remains to be fully established. In the present communication, we aimed at evaluating the estrogenic/antiestrogenic effects of raloxifene upon organization and activation of sexual receptivity, an estrogen-dependent event, in female rats. To this end, the effects of raloxifene, administered during the neonatal period, were compared with those of estrogen in terms of disruption of sexual receptivity in estrogen–progesterone-primed ovariectomized (OVX) female rats. In addition, the ability of raloxifene to induce sexual receptivity in progesterone-primed OVX females was analyzed. Similarly, the effects of the combined administration of estrogen and raloxifene were studied. Our results suggest that raloxifene does not act as estrogen upon the organization of the neuronal system involved in the control of sexual receptivity in female rats and exerted an antiestrogenic action in adult OVX estrogen-primed female rats.

Asymmetry in progestin receptor levels and sexual behavior in female rats

There are reports of hemispheric asymmetry in the control of sexual receptivity by the hypothalamus in the female rat. In the present study, we investigated whether there is an asymmetry in the distribution of progestin receptors in the hypothalamus, and whether the asymmetry in distribution is associated with receptivity as indicated by lordosis quotients. Degree of hemispheric asymmetry in hypothalamic progestin receptor (PR) levels was associated with higher lordosis quotients regardless of the direction of asymmetry. In a second study, as in the first study, degree (and not direction) of asymmetry of PR levels in the hypothalamus was associated with receptive behavior. In addition, the results suggest a possible link between left-biased asymmetry in frontal cortical PR levels and proceptive behavior. These studies are the first evidence of relationships between hemispheric asymmetry in progestin receptor levels and behavior.

The role of oxytocin release in the mediobasal hypothalamus of the sheep in relation to female sexual receptivity.

In vivo microdialysis and retrodialysis were used to investigate the role of oxytocin (OXY) release in the mediobasal hypothalamus (MBH) of the ewe in the control of sexual receptivity. Initial experiments showed that OXY release was significantly increased in ovariectomized animals treated with progesterone and oestradiol when they were sexually receptive towards males and received intromissions. No such increases were seen during tests where the ewes were receptive but the males were prevented from achieving intromission. By contrast, OXY release was significantly reduced in tests where the ewes were not receptive to the male. In a second experiment artificial vaginocervical stimulation (VCS) was found to significantly increase OXY release when the animals were treated with oestradiol and this effect was potentiated by progesterone priming. OXY release in the MBH was not significantly altered by VCS in the presence of progesterone priming alone. Plasma OXY concentrations were significantly increased by VCS following all three hormone treatments but no one treatment was significantly more effective than another. Noradrenaline release in the MBH was only significantly increased following VCS when progesterone priming was given before oestradiol treatment. No effects of VCS on release of GABA, glutamate or dopamine were seen but their basal concentrations were significantly increased by the combined steroid treatment compared to oestradiol alone. In a third experiment it was found that OXY (10 microM) infused bilaterally into the MBH of receptive ewes, by retrodialysis, significantly decreased sexual receptivity and increased the release of noradrenaline and GABA.(ABSTRACT TRUNCATED AT 250 WORDS)

Ventral tegmental lesions impair sexual receptivity in female hamsters

The ventral mesencephalon appears to be one of the sites of progesterone action in the control of sexual receptivity in female hamsters. The behavioral response to systemic progesterone was assessed in female hamsters following electrolytic lesions of portions of the ventral mesencephalon. Adult female hamsters were ovariectomized and pretested for sexual receptivity, then were given bilateral lesions aimed at the region of the ventral mesencephalon where progesterone implants have been shown to facilitate receptivity. Lesions were produced by stereotaxically lowering an electrode and applying anodal direct current of 1–2 mA for 5–20 seconds. One week later the hamsters were injected with estrogen followed 44 h later by progesterone. They were then tested for sexual receptivity. After this test, their brains were removed and histologically prepared. Lesion location was determined and lesion size was quantified with a digitizing pad. Lesions which were centered in and destroyed much of the ventral tegmental area produced the greatest lordosis impairments. Mesencephalic lesions which did not bilaterally damage the ventral tegmental area had little effect. These results support the hypothesis that the ventral mesencephalon. particularly the ventral tegmental area, is an important site for the facilitative action of progesterone on sexual receptivity in estrogen-primed female hamsters.

Male accessory gland substances and the control of sexual receptivity in female Culex tarsalis

ABSTRACT. Homogenates of accessory glands from male Culex tarsalis Coquillet (Diptera; Culicidae) were fractionated using gel filtration column chromatography. A component of low molecular weight capable of suppressing female sexual receptivity was obtained and partially characterized. Proteins present in homogenates of isolated accessory glands formed aggregates with other proteins in extracts of whole mosquitoes. Consequently, previous reports of the molecular weight of biologically active components in homogenates from accessory glands from other mosquito species may be inaccurate.When female Cx. tarsalis were mated with 3H‐leucine labelled males. radioactivity could be found throughout the body of the female 24 h after mating. Autoradiography showed that the radioactivity was incorporated into the cells of various organs, and was not specifically localized in a particular target tissue. Approximately 30% of the total radioactivity transferred to the female was found in the head and thoracic regions, and proteins from the head had a specific activity twice that of the thoracic proteins. Bioassay of isolated body parts from mated and virgin females showed that injections of head tissues from mated females into virgin females suppressed sexual receptivity. These results suggest that the head is involved in the physiological mechanisms resulting in refractory mating behaviour.

Brain catecholamine content during the estrous cycle and in steroid-primed rats

Norepinephrine (NE) and dopamine (DA) levels were measured in several estrogen concentrating brain regions over the estrous cycle and in steroid-primed ovariectomized rats under experimental conditions used to study sexual receptivity. Norepinephrine content in the ventromedial hypothalamus (VMH), lateral septum (LS) and medial preoptic area (POA) varied during the estrous cycle. The highest NE levels were found during metestrus in these brain regions. In the ovariectomized rat, NE levels were increased in the POA and LS 12 hours (hr) after the injection of 3 μg of estradiol benzoate (65% and 33%, respectively). Norepinephrine content in the POA and LS remained elevated 24 hr and 48 hr (0.5 mg progesterone at 42 hr) after treatment but were not different from control levels at 96 hr. Dopamine concentrations were not significantly altered over the estrous cycle or by the administration of estradiol benzoate in any of the brain regions studied. These results suggest that estrogen may selectively alter noradrenergic activity in brain regions that are implicated in the control of sexual receptivity and/or ovulation.

Estradiol and progesterone in the control of sexual receptivity in female rats.

Estradiol (E2) and progesterone (P) are both required for induction of sexual behavior in female rats under physiological conditions. Administration of E2 in brief pulses can induce the behavior in ovariectomized rats. P does not normally exert inhibitory or anti‐estrogenic effects on the behavior. The decline of sexual receptivity in ovariectomized E2+P‐treated rats is dependent upon the amount of E2 and P given but independent on the continued presence of either hormone. Ovariectomized animals treated with a constant amount of E2 show a behavioral rhythm which is disrupted by hypothalamic lesions and it is suggested that peptidergic neurons in the suprachiasmatic nuclei of the hypothalamus rhythmically inhibit the behavior of ovariectomized E2‐treated rats.

Stress related effects in the control of sexual receptivity and in the secretion of progesterone by the adrenals in cyclic female rats

The present study examined the acute effects of ether anaesthesia and/or blood removal by heart puncture on progesterone blood concentration at different times of proestrus and on subsequent estrous mating behavior during the night following proestrus in sham adrenalectomized and adrenalectomized 4-day cyclic female rats. A statistically significant increase in blood progesterone concentration was observed on proestrus at 09:00, 13:30 and 15:30, a very short time after heart puncture under a 3 min ether anaesthesia in sham adrenalectomized rats as compared to their adrenalectomized counterparts. Following this blood removal procedure at the preceding times a greater number of sham adrenalectomized female rats displayed mating behavior (17/20) than their adrenalectomized counterparts (11/23). It is suggested that adrenocortical related effects of ether anaesthesia and/or surgical manipulations may be involved in the display of estrous sexual receptivity in the rat.

Involvement of serotonin and γ-aminobutyric acid in the timing of estrous receptivity in the cyclic female rat

The involvement of serotonin (5HT) and γ-aminobutyric acid (GABA) in the control of estrous sexual receptivity has been investigated in the cyclic female rat. (1) When injected at 1300 hr on proestrus parachlorophenylalanine ( pCPA) specifically increased sexual receptivity as expressed by the number of receptive females between 1800 and 1900 hr and simultaneously depressed 5HT turnover. (2) A specific decrease in blood progesterone (P) concentration was observed on proestrus at 1530 hr in females treated with pCPA on proestrus at 1300 hr. (3) When injected on proestrus at 1730 hr dipropylacetate (DPA) induced a decrease in sexual receptivity between 1830 and 1900 hr in both intact and bulbectomized females but it depressed the lordosis quotient only in unoperated females. (4) An increase in the amount of γ-aminobutyric acid (GABA) in the olfactory bulbs and in the hypothalamus was noted at 1845 hr in DPA treated females. A significant decrease in the olfactory bulb GABA content occurred from 1845 to 2245 hr on proestrus. (5) The results are in favor of an involvement of 5HT and GABA in the control of the timing of sexual receptivity by the olfactory bulbs in the rat. They also suggest that interactions between P and 5HT are implicated in the control of sexual receptivity in the cyclic female rat.

5-Hydroxytryptamine and sexual behaviour

By the use of new more specific psychoactive drugs data are presented which add support for the role of 5-hydroxxtryptamine (5-HT) in the control of sexual receptivity in female mammals. Thus the 5-HT uptake blockers GEA654 and H102/09 and the 5-HT releasing agent PTR 17402 totally inhibit the receptivity induced by estrogen and progesterone. The induction of receptivity by the highly specific 5-HT receptor blocker metherzoline is also significant. These effects are correlated with the actions of the drug on extensor reflex activity and 5-HT turnover. Some of the hallucinogenic compounds stimulate pre- and postsyn ptic 5-HT receptors at low dosage but as dosage increases sexual activity is inhibited. This was 1st observed with D-LSD. Other hallucinogenic indole-alkylamines have been shown to have similar effects. Results point to the involvement of 5-HT on sexual receptivity but none define the mechanism of action of progesterone nor on which component of the 5-HT-containing neural system it acts.

Dopamine and sexual behaviour in female rats. Effects of dopamine receptor agonists and sulpiride

The effects of dopamine (DA) agonists apomorphine, ET495, CB154 and Lergotril on the sexual receptivity of ovariectomized, oestrogen-treated rats was studied. In low doses all drugs caused a marked increase in receptivity, but as the dose increased the facilitatory effects disappeared; indeed, the highest doses of each drug inhibited oestrogen/progesterone-induced receptivity. We suggest the explanation for these effects to be selective presynaptic DA receptor stimulation by the agonists at low doses while, at high doses, postsynaptic DA receptor stimulation is the dominant effect. Consistent with this view was the fact that sulpiride, a putative presynaptic DA receptor blocker, prevented the effects of low but not high doses of the agonists. These data support the concept of an inhibitory role for DA neurones in the control of sexual receptivity.

5-Hydroxytryptamine in the central nervous system and sexual receptivity of female rhesus monkeys

The role of 5-hydroxytryptamine (5-HT) in the control of sexual receptivity in female rhesus monkeys has been studied in 24 adult females paired with 6 adult males. p-Chlorophenylalanine (PCPA, 75 mg/kg or 100 mg/kg, every fourth day), a selective inhibitor of 5-HT, was found to reverse unreceptivity induced by adrenalectomy in ovariectomised, oestrogen-treated females. PCPA-treated females presented more frequently and initiated more sexual behaviour, or else they refused fewer of the male's attempts to mount. These effects were in turn reversed by 5-hydroxytryptophan (5-HTP, 20 mg/kg every second day), when this was given to PCPA-treated animals. In addition, 5-HTP given alone to ovariectomised oestrogen-treated females reduced their receptivity. Parallel biochemical experiments showed that PCPA in the doses used lowered the levels of 5-HT in the brain as measured by the levels of 5-hydroxyindole-3-acetic acid (5-HIAA) in the CSF, and that these were restored by 5-HTP. Both oestradiol benzoate (15 μg/day for 10 days) and testosterone propionate (250 μg/day or 400 μg/day for 10 days) lowered the turn-over rates of 5-HT in the brain (as measured by the probenecid test) in ovariectomised female monkeys. These effects of oestradiol on turnover were antagonised by progesterone (15 mg/day for 10 days, given with oestradiol). A substance other than an adrenal androgen has thus been found to reverse the effects of adrenalectomy on sexual receptivity in female monkeys. It is therefore possible that androgens regulate receptivity in female monkeys by modifying the activity of 5-HT-containing neural systems.

The endocrine control of reproductive behaviour in the female guppy, Poecilia reticulata peters

Twelve non-virgin females were gonadectomized and tested for sexual behaviour 5, 10, 15 and 20 weeks after the operation. Most of the females showed considerable receptive behaviour during one or more tests with a general increase in receptivity from 5 to 10 weeks. Groups of non-virgin and virgin females were tested over a period of several days immediately following partial or total gonadectomy. Females gonadectomized on the 19th day of a 24 to 27-day gestation cycle showed practically no sexual behaviour over a 10-day period of testing. Females from which only the embryos were removed on day 19 performed normal amounts of receptive behaviour. Females with embryos removed at day 11 displayed very little receptive behaviour. Virgin females, receptive at first, showed a rapid decline in receptivity 6 days after total gonadectomy. An initial decline in sexual behaviour follows gonadectomy but several weeks later sexual behaviour reappears and females may respond fully to male displays. Thus the ovary is not essential for the occurrence of complete patterns of behaviour. On the other hand, the regular cycles in non-virgin females, the persistent responsiveness of virgin females and the initial decline in receptivity after gonadectomy all suggest that the ovary exerts a regulating and perhaps stimulating influence upon a more direct control, perhaps by the pituitary. Evidence for such a direct control is provided by the finding that hypophysectomy brings about an immediate cessation of sexual behaviour. Behavioural receptivity is not correlated with the presence of corpora lutea. Periods of maximum receptivity appear to be correlated with vitellogenesis in the ovary and hence presumably with the secretion of gonadotrophic hormone by the pituitary. Apart from its effects upon ovarian development, gonadotrophic hormone may also stimulate secretion of an ovarian hormone involved in the regulation of receptivity. The ovarian hormone may in its turn have a feedback effect upon the output of gonadotrophin or some other pituitary factor directly involved in the control of sexual receptivity.

The control of sexual receptivity in female Drosophila

1. 1. This paper describes various experiments on the integration of reproductive physiology and behaviour in female Drosophila melanogaster and D. simulans. 2. 2. The sexual behaviour of females is ascribed to two distinct processes. One determines the state of receptivity, i.e. whether a female is ‘accessible’ to stimulation from the courtship of a male, the other summates the various stimuli from courtship and eventually leads to the female accepting a male. 3. 3. Females are unreceptive to males on the day of eclosion (day 0) about 25 per cent are receptive on day 1, the rest by day 2. More precise tests place the transition period between 24 and 40 hr from eclosion. In any individual the change is a sudden one; females are either fully receptive or fully unreceptive. Accordingly this change is called ‘switch-on’. 4. 4. The corpus allatum and ovaries show a growth cycle parallel to that of receptivity. Evidence is presented that increase in juvenile hormone titre is responsible for the ‘switch-on’ of receptivity. 5. 5. Virgin females remain receptive for many days, but an increasing proportion become unreceptive after the first week of adult life. ‘Switch-off’ like ‘switch-on’ is a rapid, all-or-nothing process. Females also become unreceptive immediately after mating and this inhibition of receptivity has two components, (a) an effect of copulation itself, probably mechanical, which wears off after 48 hr, (b) an effect due to the presence of live sperm, which wears off once a female has exhausted the sperm by egg laying, after some 8 to 10 days. 6. 6. Old females which have mated and used up their sperm are more often receptive than virgins of the same age. It is suggested that this is so because their corpora allata are more active and the juvenile hormone concentration is kept up above the critical level for longer. 7. 7. The situation revealed in Drosophila is compared with that found in other insects, particularly with regard to the role of the endocrine system.

The control of sexual receptivity in female cockroaches

Female receptivity and sex pheromone production are controlled by different mechanisms. In B. fumigata females the corpora allata control pheromone production. The female's pheromone releases courtship behaviour in the male; he raises his wings exposing his tergum and apparently releases a pheromone. The receptive female is attracted to the male and mounts and ‘feeds’ on his tergum. The mounting and feeding behaviour, which is indicative of female receptivity, is not directly controlled by the corpora allata. Receptivity in N. cinerea and L. maderae is determined by some event, presumably in the brain, which occurs at about the same time as the onset of activity of the corpora allata. It is suggested that the neurosecretory system is involved in acceptance of the male by the female.