Coitus-induced Ovulation Research Articles

New insights of the role of β-NGF in the ovulation mechanism of induced ovulating species.

The type of stimuli triggering GnRH secretion has been used to classify mammalian species into two categories: spontaneous or induced ovulators. In the former, ovarian steroids produced by a mature follicle elicit the release of GnRH from the hypothalamus, but in the latter, GnRH secretion requires coital stimulation. However, the mechanism responsible for eliciting the preovulatory LH surge in induced ovulators is still not well understood and seems to vary among species. The main goal of this review is to offer new information regarding the mechanism that regulates coitus-induced ovulation. Analysis of several studies documenting the discovery of β-NGF in seminal plasma and its role in the control of ovulation in the llama and rabbit will be described. We also propose a working hypothesis regarding the sites of action of β-NGF in the llama hypothalamus. Finally, we described the presence of β-NGF in the semen of species categorized as spontaneous ovulators, mainly cattle, and its potential role in ovarian function. The discovery of this seminal molecule and its ovulatory effect in induced ovulators challenges previous concepts about the neuroendocrinology of reflex ovulation and has provided a new opportunity to examine the mechanism(s) involved in the cascade of events leading to ovulation. The presence of the factor in the semen of induced as well as spontaneous ovulators highlights the importance of understanding its signaling pathways and mechanism of action and may have broad implications in mammalian fertility.

Expression of α4 and α7 nicotinic receptors in the brainstem of female rabbits after coitus

Coital signaling in the female rabbit involves sequential events in the brainstem and hypothalamus, resulting in a massive release of hypothalamic gonadotropin-releasing hormone (GnRH) that peaks within 1–2 h after mating. The neural connections between coitus and GnRH release involves norepinephrine (NE) and acetylcholine (ACh) since administration of antagonists against NE (dibenamine or phentolamine) or ACh (atropine, α-bungarotoxin (α-BTX) or scopolamine) blocks or attenuates ovulating events. Moreover, hypothalamic NE release and brainstem tyrosine hydroxylase (TH, the rate-limiting enzyme for NE synthesis) expression in the noradrenergic areas increase prior to, or in concert with, the preovulatory GnRH surge. How ACh is involved in the control of ovulation in the rabbit is lesser known. In the present study, the number of brainstem neurons expressing TH, α4 and α7 subunits of the nicotinic ACh receptor (nAChR) before and after coitus was determined by immunocytochemistry. Compared to non-mated female rabbits, the number of α4, α7 and TH single-labeled neurons as well as α4/TH and α7/TH double-labeled neurons increased in the A1, A2 and A6 brainstem noradrenergic areas at 1 h, but not 2 h, after coitus. The results suggest that the participation of ACh in the control of coitus-induced ovulation may include activation of α4β2 and α7 nAChRs in neurons within or adjacent to the brainstem noradrenergic areas in female rabbits.

Manipulation of reproductive functions in male and female camels

Old World camels ( Camelus dromedarius or dromedary and Camel bacterianus or Bacterian camel) have been used for millenia in geographic areas and climates for which they are uniquely adapted. Human survival and trade in these areas has been dependent on the use of camels as beasts of burden, in agriculture, and as a source of milk, meat and fiber. Systematic efforts to apply modern aspects of genetic breeding for improved fertility and productivity are sparse and difficult to comprehend and adopt by nomadic breeders and almost subsistence farmers, in whose hands the majority of camels may be found. As a prerequisite for improvements in reproductive management, a status report is given on the following subjects: puberty, breeding season, the estrous cycle, coitus-induced ovulation and its control with intravaginal infusion of normal ejaculates, those from vasectomized males, and seminal plasma, utero-ovarian relationships and pregnancies. Ovulations can be induced by luteinizing hormone (LH), human chorionic gonadotrophin (hCG) and gonadotrophin releasing hormone (GnRH), and superovulations with equine chorionic gonadotrophin (eCG) (pregnant mares' serum gonadotrophin; PMSG). Priming with progesterone (PRID, intravaginally) may enhance superovulatory responses, as does treatment at the correct phase of follicle wave development and the use of hCG. Recipients for embryo transfer can be prepared by using PRID, and hCG to induce ovulations. Embryos can be successfully recovered and transferred by non-surgical methods. Information on males is added which includes data on artificial insemination, involving semen collection via electro-ejaculation, semen characteristics and evaluation methods, deep freezing semen and insemination techniques. Modern methods of reproductive manipulation require sedation and analgesia, for which recently developed a 2-agonists, such as detomidine, are well suited.

Coitus-induced ovulation and its implications for estimates of some reproductive parameters.

It is estimated here that, at the time of conception, the mean coital rate of young women who subsequently bear DZ twins is about 6% higher than that of the general population of young married women. This differential seems too small to account wholly for the greater promptness in conceiving DZ twins. Accordingly, it is suggested that coital rate is associated with DZ twinning in two ways. The major link seems to be indirect and mediated by erotic response which causes an increase in gonadotrophin levels and thus in double ovulation. In a minority of cases, frequent coitus may give rise to DZ twins via superfecundation, but it seems that, in human beings, the corpus luteum of one ovum will usually inhibit fertilization of any further ova after a short interval. The evidence presented here, though indirect, seems to suggest that, under particularly erotic conditions, double ovulation is sometimes induced. It seems reasonable to infer that coitus also occasionally provokes or accelerates single ovulations, thus impugning some rhythm methods of contraception. But there seems no very good evidence that rape induces ovulation. Some notes are added on the implications of induced ovulation for estimates of fecundability and of the length of the fertile period.

Pregnancy as a Result of Rape

AbstractDespite the fact that rape literature has flourished since 1975, most sources contain little or no reference to the issue of rape resulting in the victim's pregnancy. This work addresses several facets of the problem of pregnancy from rape. Literature citations of statistical frequency and medical theories regarding the physiology of the process, particularly coitus-induced ovulation theories, are presented. Implications for health care and social service professionals are examined, with an emphasis on how reporting practices affect intervention protocols. Finally, political trends are discussed, especially changes in the frequency with which pregnancy from rape has been documented since legislative policies restricted Medicaid funding for abortion.

Olfactory environment and coitus-induced ovulation and/or luteinization in the cyclic female rat.

The role of pheromones in the process of ovulation and/or luteinization induced by coitus was studied in female rats primed with estradiol benzoate (EB) and early mated during 4-day cycles. The effects of coitus were evaluated by using 1) the proportion of females displaying postovulatory corpora lutea (POCL) and/or luteinized unruptured follicles (LUF), and 2) the ovulation coefficient (OC) computed in each female by dividing the number of POCL by the total number of POCL and LUF. A greater proportion of females displayed ovulation and/or luteinization following coitus than those given EB only. This proportion was slightly but significantly increased when females were exposed to bedding soiled with 5 ml of male urine prior to mating, an effect prevented by complete olfactory bulbectomy. However, in the females given EB only, the pheromonal stimulus remained inefficient. Weak ovulatory effects of coitus, as assessed by low OC values, were noted whether the females were exposed or not to male urine. An increase in the frequency of lordosis occurred after olfactory bulbectomy, but no significant changes in OC values were observed in this experimental group. It was concluded that pheromones, act as a primer on the neuroendocrine mechanisms governing ovulation in the cyclic female rat, as in other species of rodents.

Inhibitory effect of charcoal-treated aqueous porcine corpus luteum extract upon ovulation in the rabbit.

AbstractAdministration of charcoal-treated aqueous extract of porcine corpus luteum on Days 0, 1, and 2 after mating inhibited coitus-induced ovulation in the rabbit. Inhibition of ovulation was evidenced by a significant (P < 0.01) inhibition of the coitus-induced rise in serum progesterone and lack of formation of corpora lutea. Administration of charcoal-treated heart or lung extract had no significant effect upon the formation of corpora lutea or on the coitus-induced rise in serum progesterone. Administration of the same extract 3 and 4 days after coitus-induced ovulation had no significant effect upon serum progesterone and further formation of corpora lutea. These data are consistent with the existence of an LH binding inhibitor in porcine corpus luteum extract which acts to inhibit the ovulatory response to the coitus-induced LH surge.

Coitus-induced ovulation and sex ratio in man

It is hypothesised that the occurence of coitus-induced ovulation could be an important factor affecting the sex ratio in human progeny. The slight preponderance of males in human sex ratio at birth, 106 : 100, could be influence considerably by the coitus-induced occurence.

The biological effects of two antagonistic analogues of luteinizing hormone releasing hormone

Two highly potent antagonists of LHRH, as evaluated by inhibition of LHRH-induced LH release in primary rat pituitary cell culture, were studied in a range of in vivo test systems. The compounds were: z-[Gln 1,des-His 2, D-Pse 6,des-Gly 10]-LHRH ethylamide, where D-Pse = Threo-D-phenylserine and Boc-[Ser-(Bzl) 1,des-His 2, D-Trp 6]-LHRH. Both materials were synthesized either as acetate or hydrochloride salts. Where both salts were examined in a single assay, slight potency differences were sometimes seen. Irrespective of salt form employed, both compounds were effective antagonists of ovulation induced in rabbits by exogenous LHRH; however, large doses failed to inhibit coitus-induced ovulation. Spontaneous ovulation in rats and hamsters was blocked by administration of either compound during the critical period on the day of proestrus. Estrous cycles were disrupted in rats by either peptide administered over 10-day periods; this treatment was followed by ovarian atrophy, and thyroid and adrenal hypertrophy; pituitary weights were increased slightly, while uterine weight remained unchanged. Unexpectedly, neither peptide affected established pregnancy in rats.

A Study of the Relationship Between Coitus and the Luteinizing Hormone Surge

Twenty-seven wives participating in a study of sexual activity patterns had identifiable shifts in basal body temperature and midcycle surges of serum luteinizing hormone (LH). When sexual activity data were examined using the LH surge as a centering point, it was observed that the day before the LH surge had only an average probability of coitus and organism. These findings suggest that neither coitus nor orgasm often triggers ovulation in humans. This cannot be taken as evidence that coitus-induced ovulation never occurs.

Coitus-induced ovulation

This article reviews evidence of coitus-induced ovulation. Maintenance of reproductive efficiency by more than 1 mechanism for triggering ovulation is interpreted as an evolutionary phenomenon aimed at ensuring the survival of the species. In earlier research estrogen levels or progesterone output were believed to regulate the ovulatory luteinizing hormone (LH) release and the length of the receptive period in spontaneous ovulators; more recently the effect of neural olfactory and emotional stimuli has been recognized. The neuroendocrine systems involved in spontaneous and reflex-induced ovulation include the hypothalamic-hypophyseal-gonadokinetic system and the neurohormonal pathways for coitomimetic stimuli. In spontaneously ovulating rodents the stimulus of coitus serves as an inducer for pseudopregnancy. The translation of vaginal stimulation into gonadomimetic humoral messages released from the hypothalamus and/or the posterior pituitary for the liberation of LH and prolactin is not completely understood. Nervous or biochemical influences resulting from coitus may even more directly affect ovarian functions by local sympathetic reflexes or by biochemical components of the ejaculate. In coitus-induced ovulation central nervous and/or peripheral autonomic nervous involvement may interact to push ovarian follicles toward maturation and ovulation or may help to ovulate nearly ripe or ripe follicles as a result of cohabitation. Acceptance of coitus-induced ovulation in humans renders rhythm methods of fertility control unreliable. In 1 large study of pregnancies resulting from rape 33-46% of conceptions occurred during what should have been a safe period. Emotions may also play a role in facilitating or predisposing to coitus-induced ovulation. There is a need for further biochemical statistical and demographic analyses of the frequency and sociologic importance of coitus-induced ovulation in humans.

Periodicity of sexual desire in relation to time of ovulation in women.

A review of several studies attempting to determine the existence of a period of increased sexual desire during the menstrual cycle and its relationship to ovulation indicates that peaks have been reported prior to menstruation and after menstruation; studies on sexually inactive women report peaks at midcycle. Terminological ambiguities regarding sexual desires are partly responsible for differences in the various studies reviewed. Psychological and social factors and physical factors (such as an increased amount of mucus in the vagina during the follicular phase increased congestion in pelvic tissues during the luteal phase and hormonal variations) and research methodology (some studies requiring sexual abstinence for certain lengths of time) are also responsible for variations in results. Coitus-induced ovulation has also been suggested by studies on rape victims and by rat experiments. Sexual desire may differ during the luteal and follicular phases preferences may differ among women regarding the phases and consequently what they experience (and define) as sexual desire may vary accordingly. Alterations in desire may be caused by contraceptive methods the rhythm method forcing suppression of desire during the follicular phase and the progesterone in oral pills causing enhancement in the luteal phase or suppression of desire because of the lack of follicular phase.

Influence of copulation on time of ovulation in women

Data from animal studies and clinical literature suggesting that coitus-induced ovulation may occur in women is reviewed. Although a spontaneous ovulator the rat has displayed ovulation following coitus with a rise in plasma LH 5 to 10 minutes after intercourse and it has been shown that reflex ovulation in the rat is a function of the intensity of vaginal and cervical stimulation. Direct evidence evidence of spontaneous human ovulation at midcycle (range 8 to 10 days) has been found while other studies indicate that ovulation may occur during any day of the menstrual cycle and that copulation may be the initiator of the response. Conception following rape has been found to occur at any stage. The intensity of coitus during rape is likely to be greater than normal coitus and this increased intensity could be an important factor in human reflex ovulation. Coitus-induced ovulation may be a factor in the observed failures of the rhythm method. Menstrual cycle length in both monkeys and women is extremely variable (24 to 38 days for humans) but it is generally agreed that the postovulatory period is fairly constant with an average length of 14 days. Coitus-induced ovulation early in the cycle would produce a short cycle and long cycles would result if reflex ovulation occurred later in the preovulatory phase. Research of rhesus monkeys kept isolated from males revealed that only 50% ovulated. If women were similarly isolated the number showing anovulatory cycles might increase considerably. Studies of human ovulation should include records of the effects of coital activity and its influence on results.

Blockade of ovulation in the rabbit with catecholamines and sympathomimetics.

SummaryElevation of sympathetic tonus by injecting various catecholamines blocks coitus-induced ovulation in rabbits. Epinephrine, isoproterenol, and serotonin block ovulation when given at various times after mating. A dose of epinephrine (300 μg/kg) which is well tolerated by rabbits at other times was lethal to 100% of does when administered 5 min after mating. Norepinephrine and amphetamine do not prevent ovulation when given at 0-1 min postcoitum.

Pregnancy following coital-induced ovulation in a spontaneous ovulator.

Ovulation induced in the immature rat by pregnant mare's serum can be prevented by chlorpromazine. Coitus induces ovulation in such animals, and ovulation so induced may result in pregnancy. Both implantation and pregnancy appear to be normal although the duration of gestation may be prolonged. Decidual response also is produced in the immature rat after coitus-induced ovulation. We suggest that the reflex release of luteinizing hormone may occur in Primates after coitus.

Chromosome Deterioration in Ageing Eggs of the Rabbit

COITUS-INDUCED ovulation in the rabbit ensures that fertilization of nearly all eggs is initiated within 2 or 3 h of their arrival in the fallopian tube. When ovulation was induced by hormone injection, and coitus permitted at the time of ovulation (10 h after injection), fertilization began about 5 h later and continued for a further 3–5 h, eventually involving a little over 70 per cent of the eggs1. As a result, therefore, of the delay in the time of coitus, eggs underwent 6 or 7 h ageing before fertilization was initiated; fertilization nevertheless occurred in all but about 30 per cent of eggs. Despite this relatively small drop in fertilization rate there is evidence that fertility in the rabbit is seriously impaired by the delay of coitus. Chang2 observed that 60 per cent of eggs failed to implant and that more than half the implanted embryos died before term, and Hammond3 recorded an 80 per cent reduction in the mean number of young born. To some extent, the reduced fertility can be attributed to the occurrence of polyspermy and polygyny, conditions that lead to the highly lethal state of triploidy in the embryo, but this would not account for embryo but this would not account for embryo loss of more than about 16 per cent4,5.