Ejaculatory Series Research Articles

Threshold for copulation-induced analgesia varies according to the ejaculatory endophenotypes in rats.

Analgesia may be modulated by multiple internal and external factors. In prior studies, copulatory-induced analgesia was demonstrated using the vocalization threshold to tail shock (VTTS) in male and female rats. Three ejaculatory endophenotypes have been characterized in male Wistar rats based upon their ejaculation latency (EL). Since intromissions and ejaculations produce analgesia, and these copulatory patterns are performed with different frequency depending on the male's ejaculatory endophenotype, we hypothesized that copulation-induced analgesia would vary in relation to these endophenotypes. In the present study, we used three groups according to the EL (medians): rapid ejaculators (236 s; n = 21), intermediate ejaculators (663.2 s; n = 20) and sluggish ejaculators (1582.2 s; n = 8). Our aim was to evaluate whether copulation-induced analgesia is related to the ejaculatory endophenotypes during two consecutive ejaculatory series (EJS). In the first EJS, the VTTS of the rapid ejaculators was significantly higher than that of intermediate and sluggish rats. At the onset of the second EJS, the VTTS of the rapid and intermediate ejaculators was significantly higher than that of the sluggish rats. No differences in VTTS were observed during the first or second post-ejaculatory intervals among the three groups. These findings provide evidence that the more intromissions that occurred per unit time, the higher was the level of analgesia.

Effects of Dracaena arborea (Dracaenaceae) on sexual dysfunction in 4 weeks hyperglycemic male rats

ObjectiveTo investigate the effects of Dracaena arborea (D. arborea) on the sexual behavior parameters in experienced type-1 diabetic rats. MethodsAqueous and ethanol (100 and 500 mg/kg respectively) extracts of dried root barks of D. arborea, sildenafil citrate (1.44 mg/kg), trimethylamine-N-oxide (TMAO, 20 mg/kg) and distilled water (10 mL/kg) were orally administered to 4 weeks streptozotocin-induced diabetic rats. Mount latency and frequency (ML, MF), intromission latency and frequency (IL, IF) and post-ejaculatory interval (PEI) were measured by ejaculatory series during 90 min once a week for 4 weeks. Glycemia was determined at the beginning and at the end of the treatment. ResultsD. arborea did not show any major antihyperglycemic effects. Compared to the control group, a significant (P<0.05–0.001) increase in MF and IF was noticed in rats treated with sildenafil citrate (89.71% and 90.07% respectively), aqueous (500 mg/kg, 88.08% and 88.74% respectively) and ethanol (100 mg/kg; 89.53% and 89.17 respectively) extracts of D. arborea after two weeks (series 1) of treatment. ML, IL and PEI were significantly (P<0.05–0.001) decreased after 4 weeks of daily treatment [sildenafil citrate (96.31, 96.31% and 34.98%), and D. arborea aqueous 500 mg/kg (94.33, 94.33% and 66.60%) and ethanol extracts 100 mg/kg (96.98, 97.08% and 64.26%)]. ConclusionsThese aphrodisiac potentials of D. arborea in experienced diabetic rats could be due to the antioxidant and androgenic properties of phenols, flavonoids, saponins and sterols revealed in the plant extracts.

The Antidepressants Fluoxetine and Bupropion Differentially Affect Proceptive Behavior in the Naturally Cycling Female Rat

Fluoxetine, like other selective serotonin reuptake inhibitors, inhibits women's sexual desire and female rats' sexual behavior. Bupropion produces pro-sexual effects in women with and without depression, and yohimbine increases men's and male rats' sexual motivation, but their effects on female rats' proceptivity are unknown. To investigate the effects of fluoxetine, bupropion, and yohimbine on proceptivity and receptivity in the naturally cycling female rat. We studied the effect of chronic (minimum 14 days) fluoxetine (1.25 mg/kg, subcutaneous) and bupropion (5 mg/kg, intraperitoneal) and acute yohimbine (1 mg/kg, intraperitoneal) on sexual behavior of female rats selected in natural proestrus during an ejaculatory series. We also analyzed the effects of these treatments on locomotor activity. The main outcome measures were frequencies of hops/darts and ear wiggling, lordosis quotient and intensity, and locomotor activity. Fluoxetine inhibited ear wiggling and hopping/darting, while bupropion stimulated hopping/darting. These treatments did not modify the lordosis quotient and its intensity. Yohimbine did not change any aspect of female sexual behavior. At the doses and treatments used, fluoxetine and bupropion did not alter locomotor activity or disturb the length of the estrous cycle; however, yohimbine inhibited locomotor activity. The motivational components of female sexual behavior are more sensitive than the receptive components to the inhibitory actions of fluoxetine. Bupropion selectively stimulated hopping/darting, while yohimbine lacked an action on female sexual behavior.

Anandamide Transforms Noncopulating Rats into Sexually Active Animals

Noncopulating (NC) male rats are apparently normal and healthy animals that will not mate despite repeated exposure to sexually receptive females. Several lines of evidence suggest the involvement of endogenous opioids in this sexual inhibitory state. Endogenous opioids and endocannabinoids are neuromodulators of neurotransmitter release, although through different mechanisms. To establish if the endocannabinoid anandamide was able to induce sexual behavior expression in male rats classified as noncopulators. NC male rats were intraperitoneally (i.p.) injected with anandamide or vehicle and tested for copulatory behavior with a receptive female during 120 minutes. Fourteen days after anandamide or vehicle injection, the animals were subjected to a second sexual behavior test during 60 minutes. The percentage of rats showing male sexual behavior responses: mount, intromission, ejaculation, and copulation resumption after ejaculation and the specific sexual behavior parameters were quantified. Anandamide injection induced sexual behavior expression in 50% of previously NC rats, while the NC animals injected with vehicle did not show sexual behavior. The responding animals executed several successive ejaculatory series and were still capable of showing sexual behavior 14 days after anandamide injection. Copulation in these rats (the first copulatory series) was characterized by a large number of mounts and intromissions preceding ejaculation, as well as by statistically significant increases in the latencies to mount, intromit, and ejaculate when compared with the sexual performance of sexually naïve animals copulating for the first time. The endocannabinoid anandamide transforms previously NC rats into sexually active animals, capable of showing sexual behavior in a long-lasting manner. Only half of the NC population responds to anandamide injection, suggesting that different mechanisms underlie the sexual inhibition of NC rats. The endocannabinoid system seems to play a role in the regulation of male rat sexual behavior expression.

Fluoxetine Chronic Treatment Inhibits Male Rat Sexual Behavior by Affecting Both Copulatory Behavior and the Genital Motor Pattern of Ejaculation

Selective serotonin reuptake inhibitors (SSRIs) are antidepressants that cause sexual dysfunction. The SSRI fluoxetine (FLX) appears to particularly affect the ejaculatory response. Ejaculation is regulated both at brain and spinal levels. To study the acute and chronic effects of FLX on male rat copulatory behavior, trying to distinguish between brain and spinal cord FLX-induced changes on the ejaculatory response. Sexually experienced male rats were intraperitoneally injected with 5 or 10 mg/kg FLX and tested for sexual behavior during 60 minutes on days 1, 7, and 14 of treatment. After a 2-day drug holiday, the males chronically treated with the high FLX dose were spinalized to record spontaneous and mechanically evoked genital motor patterns of ejaculation (GMPEs). In addition, independent groups were used to evaluate the acute effects of 1, 3, or 10 µg/rat FLX (intravenously) on the GMPE. Number of ejaculatory series and their parameters; electromyographic recordings of the GMPE in the bulbospongiosus muscles and their parameters. Acute FLX injection slightly affected sexual behavior display and dose-dependently inhibited the expression of the GMPE. Chronic FLX treatment did not inhibit copulation but produced deficits in the parameters related to ejaculation after the high dose. In these animals, the response capacity of the spinal generator of ejaculation (SGE) as well as the number of discharges in the GMPE was decreased as a result of chronic FLX treatment. Chronic FLX treatment produces inhibitory effects on male rat copulation, particularly on ejaculation, some of which are exerted directly at the SGE.

Copulatory behaviour of the bank voleMyodes glareolus: matings with one and two males do not make a difference

In promiscuous species in which females mate with more than one male during oestrus, males may increase their sperm expenditure or change their copulatory behaviour in response to the risk of sperm competition. I used an experimental approach to investigate the pattern of copulatory behaviour of the bank voleMyodes glareolus Schreber, 1780 depending on whether the female mated with one or two males. The work showed that the copulatory period of the bank vole lasted about 80 minutes and consisted of 4–5 ejaculatory series, with multiple intromissions preceding ejaculation. There were no significant changes in number of intromissions across the first four ejaculatory series, but I did find a relationship between number of intromissions and first ejaculation latency; also, ejaculation latencies grew shorter as the ejaculatory series proceeded. Litter size did not differ significantly between females that mated with one male and those mating with two, nor did the reproductive success of males that mated with the same female. Mating with an oestrus female appears to be advantageous for bank vole males even if they mate as the second one, and the risk of sperm competition did not trigger changes in male copulatory behaviour. The similar durations of the copulatory period and patterns of change of ejaculation latencies during copulations with one and two males point to the role of the female in temporal copulatory behaviour of the bank vole.

Muscarinic receptor antagonism at the spinal cord level causes inhibitory effects on male rat sexual behavior

The role of cholinergic neurotransmission in male rat sexual behavior at the brain level has been studied by several researchers. However, little is known about its role at the spinal cord level. In this study, the effects of the intrathecal (IT) administration of the muscarinic receptor antagonist subtypes (MRAs) methoctramine (Meth), tropicamide (Trop) and 4-DAMP on male rat sexual behavior were evaluated during three ejaculatory series. Meth and Trop are preferring antagonists for the M2/M4 receptor subtypes, and 4-DAMP is a preferring antagonist for the M3 receptor subtype. All the MRAs tested noticeably inhibited male rat copulatory behavior, reflected by a reduction in the number of animals engaging in sexual behavior and a gradual decrease in the number of animals able to ejaculate. Significant increases in intromission latency (IL), ejaculation latency (EL) and post-ejaculatory interval (PEI) were observed. The ranking of inhibitory potency in all recorded parameters was Meth ≥ 4-DAMP > Trop. In theory, the effects of Meth and Trop could be a result of interaction with M2/M4 receptors. However, given that the M2 receptor constitutes the greatest population of muscarinic receptors at all spinal cord sites and given the high affinity for Meth on M2 receptors, the high potency in the inhibitory effects of Meth is indicative of the special role of M2 spinal receptors in the implementation of this behavior. The weaker effects of Trop could be linked to the smaller population of M4 receptors in the spinal cord, but some interaction with M2 receptors is probable. Since some differences in the pattern of inhibitory response between Meth and 4-DAMP were observed in this and a previous study, a possible role for M3 receptors must be considered. The data obtained in this study confirm the facilitating effect of acetylcholine (ACh) at the spinal cord level on male rat sexual behavior through muscarinic mechanisms, with an important influence on ejaculatory processes. These data support the hypothesis of the modulating role of ACh on male rat sexual behavior at the spinal cord level.

Turnera diffusa Wild (Turneraceae) recovers sexual behavior in sexually exhausted males

Ethnopharmacological relevance In folk medicine , Turnera diffusa Wild ( Turnera diffusa, Turneraceae) is considered as an aphrodisiac, but its ability to restore copulation in sexually inhibited subjects has not been reported. Aim of the study To determine whether Turnera diffusa recovers sexual behavior in sexually exhausted (SExh) male rats and to identify the main components in an aqueous extract. Materials and methods SExh males were treated with Turnera diffusa, 20–80 mg/kg, yohimbine, 2 mg/kg, or vehicle. Results Yohimbine and Turnera diffusa (80 mg/kg) significantly increased the percentage of males achieving one ejaculatory series and resuming a second one. In addition, Turnera diffusa significantly reduced the post-ejaculatory interval. These effects were not associated to an increase in locomotor activity or anxiety-like behaviors. The HPLC–ESI-MS analysis showed the presence of caffeine, arbutine, and flavonoids as the main compounds in the active extract. Conclusion The results support the use of Turnera diffusa as an aphrodisiac in traditional medicine and suggest possible therapeutic properties of Turnera diffusa on sexual dysfunction. The flavonoids present in active extract may participate in its pro-sexual effect, which is analogous to those produced by yohimbine, suggesting a shared mechanism of action.

Aromatase inhibition during adolescence reduces adult sexual and paternal behavior in the biparental dwarf hamster Phodopus campbelli

Previous studies have failed to identify an activational role for estradiol in the paternal behavior of Phodopus campbelli fathers. However, none of these studies addressed a developmental role that estradiol might play in establishing paternal behavior in this species. Males were orally administered the aromatase inhibitor letrozole (1 mg/kg/day) for three days at 18, 34, or 90 days of age. As adults, males were tested for paternal and sexual behavior. Letrozole treatment at 18 days resulted in males that spent less time huddling over pups during the birth, and had higher pup losses and male-biased pup survival for the first litter. Letrozole treatment at 34 days resulted in males that had altered sexual behavior; males had a longer interval between mounts and between intromissions, and took longer to achieve ejaculations over the first three ejaculatory series. Furthermore, these males sired smaller first litters and produced second litters with a male-biased sex ratio. Males treated with letrozole as adults showed a modest increase in paternal care during the birth, but pup development and survival were not altered. There was no effect of treatment on attack or retrieval behavior either as sexually naive adults or as new fathers. Thus, the results of the present study suggest that estradiol acts during adolescence to establish the normal expression of midwifery behavior and sexual behavior during adulthood.

Female Meadow Voles, Microtus pennsylvanicus, Experience a Reduction in Copulatory Behavior During Postpartum Estrus

AbstractIn many small mammalian species, females undergo postpartum estrus (PPE), mate, and become pregnant soon after delivering a litter. Mating during PPE implies a trade‐off between attending to the new litter and leaving that litter to mate. We tested the hypothesis that copulatory behavior is faster when a female mates during PPE than when it mates outside of PPE, during male‐induced estrus (MIE), a time when it is not lactating. We compared several variables of copulatory behavior in female meadow vole mating during both PPE and MIE. Females in PPE received significantly fewer intromissions, with shorter intervals between intromissions. Each ejaculatory series was also shorter for females in PPE. As a consequence, the total amount of time devoted to copulation was much shorter for females in PPE than for those in MIE. These data support the hypothesis that female meadow voles are able to reduce their copulatory behavior during PPE.

Pharmacological and physiological aspects of sexual exhaustion in male rats.

The present article reviews the current findings on the interesting phenomenon of sexual satiety. Knut Larsson in 1956 reported on the development of sexual exhaustion in the male rat after repeated copulation. We have studied the process and found the following results. (1) One day after 4 hours of ad libitum copulation, two-thirds of the population showed complete inhibition of sexual behavior, while the other third displayed a single ejaculatory series from which they did not recover. (2) Several pharmacological treatments, including 8-OH-DPAT, yohimbine, naloxone and naltrexone, reverse this sexual satiety, indicating that the noradrenergic, serotonergic and opiate systems are involved in this process. Indeed, direct neurochemical determinations showed changes in various neurotransmitters during sexual exhaustion. (3) Given enough stimulation, by changing the stimulus female, sexual satiety was prevented, suggesting that there are motivational components of the sexual inhibition that characterizes sexual exhaustion. (4) The GABA antagonist bicuculline, or the electrical stimulation of the medial preoptic area, did not reverse sexual exhaustion. These data suggest, on the one hand, that sexual exhaustion and the postejaculatory interval (which is shortened by bicuculline administration) are not mediated by similar mechanisms and, on the other, that the medial preoptic area does not regulate sexual satiety. (5) The androgen receptor density in brain areas closely related to the expression of masculine sexual behavior, such as the medial preoptic nucleus, was drastically reduced in sexually exhausted animals. Such reduction was specific to certain brain areas and was not related to changes in the levels of androgens. These results suggest that changes in brain androgen receptors account for the inhibition of sexual behavior present during sexual exhaustion. (6) The recovery process of sexual satiety after 4 hours of ad libitum copulation reveals that, after 4 days, only 63% of the males are able to show sexual behavior while after 7 days all animals display copulatory activity.

The development of olfactory conditioned ejaculatory preferences in the male rat: II. Parametric manipulation of conditioning session number and duration

We have previously demonstrated that repeated pairing of a neutral odor with copulation produces a subsequent conditioned ejaculatory preference (CEP) for females bearing that odor. The present study examines the course of CEP development. In Experiment 1, Long–Evans male rats were allowed access to almond-scented, sexually receptive females for either one, five, or nine conditioning sessions that were 30 min in duration. Males given five or nine sessions displayed significant CEPs. In Experiment 2, male rats were given a single conditioning session with multiple almond-scented females until either a duration (60, 120, 180, or 240 min) or copulatory criterion (two, four, or six ejaculatory series) was satisfied. Males that received 120-, 180-, or 240-min sessions or four ejaculations displayed significant CEPs; males that received two or six ejaculations displayed a trend for CEPs. Analysis of effect size estimates revealed that the strongest CEPs were produced by 120 min of copulation or four ejaculations. In Experiment 3, males receiving nine conditioning sessions each 30 min in duration displayed a more enduring CEP than did males receiving a single conditioning session 240 min in duration. These data suggest that early sexual experiences have particularly powerful influences on subsequent sexual preferences and that the development of sexual preferences are influenced by interactions between CS–UCS pairings and motivational variables.

The nature of the conditioned response mediating olfactory conditioned ejaculatory preference in the male rat

We have developed a model to study the influence of conditioning on sexual partner preference in the rat. In this model, pairing a neutral odor (almond) with copulation to ejaculation produces a subsequent preference to ejaculate with females bearing that odor. We refer to this phenomenon as a conditioned ejaculatory preference (CEP). The present study investigates the nature of the conditioned response that mediates CEP. Given equal mount and intromission distributions, but an unequal ejaculation distribution, we hypothesized that two mechanisms could account for CEP: facilitated ejaculation or selective ejaculation. To test these hypotheses, we examined the effect of omitting the olfactory conditioned stimulus (CS) or applying it to a nonreceptive female. Males trained with the CS paired with copulation (paired-trained males) failed to display evidence of delayed ejaculation when copulating with unscented females. Conversely, paired-trained males displayed CS-elicited copulatory behavior with CS-bearing nonreceptive females. In addition, we re-analyzed the data from the copulatory preference tests of previous experiments for CEP-displaying males. Again, we failed to find evidence of facilitated ejaculation with the scented female. However, the time between the last mount or intromission and ejaculation was increased if either occurred with the scented female. Furthermore, more mounts were directed towards the scented female near the end, but not at other points, of an ejaculatory series. These findings suggest that the paired-trained males attend to the scented female near the point of ejaculation, and are consistent with the hypothesis that CEP is mediated by selective ejaculation.

Multiple Ejaculations and Chronic Fluoxetine: Effects on Male Rat Copulatory Behavior

WIESELER FRANK, J. L., S. E. HENDRICKS AND C. H. OLSON. Multiple ejaculations and chronic fluoxetine: effects on male rat copulatory behavior. PHARMACOL BIOCHEM BEHAV 66(2) 337–342, 2000.—Male rats were treated with fluoxetine (FLX) or vehicle daily for 14 days and copulatory behavior tested on day 15. Rats were either mated to three ejaculations or to sexual exhaustion. Both standard measures and the mount bout analysis were used to evaluate the effects of the chronic FLX on male rat copulatory behavior. Only 56.25% of the animals treated with FLX achieved three ejaculations. FLX inhibited the consumatory aspect of male sexual behavior, especially the ability to achieve three ejaculations, but there was no effect on the propensity of the male to pursue the female. These differences were observed for the first three ejaculations. Analysis of the last three ejaculations in those animals that mated to exhaustion did not reveal an effect of FLX. The behavioral pattern of FLX-treated animals during the first three ejaculations resembled that observed during the last three ejaculatory series in the vehicle-treated animals that mated to exhaustion. The results are discussed in terms of the serotonergic effects on male rat sexual behavior.

Temporal pattern of recovery from sexual satiety in male golden hamster ( Mesocricetus auratus)

In male rodents, copulatory activity ad lib leads to a complete inhibition of sexual behaviour performance known as sexual satiety. On the other hand, male hamsters display a peculiar copulatory pattern known as Long Intromission (LI) after being exposed to repeated mating. In this study, the characteristics of the temporal recovery of sexual behaviour after a sexual satiety test and the possible relationship between the presence of LI and the inhibition of sexual behaviour were analysed. Fifty males were exposed to repeated mating until they reached a criterion for sexual satiety. Thereafter, they were divided in several groups and retested for sexual activity after a period of 24, 48, 72, and 96 h. During the sexual satiety test LI appeared after nine ejaculatory series, with a mean latency of 18 min. Twenty-four hours after the satiety test, all the subjects (Ss) displayed copulatory activity, and LI appeared after a mean of 2.5 ejaculations with a mean latency of 9.1 min, whereas at 48 h, only 20% of Ss displayed sexual activity. During the 72-h period, the results obtained show a clear trend towards normalisation, and finally, at 96 h, all the sexual parameters were fully restored. The data showed that there was a close relationship between sexual inhibition and the presence of LI, and demonstrated that full recovery of sexual behaviour was reached 96 h after the sexual satiety test.

Appetitive and Consummatory Sexual Behaviors of Female Rats in Bilevel Chambers: II. Patterns of Estrus Termination Following Vaginocervical Stimulation

Copulation with intromission or manual vaginocervical stimulation (VCS) shortens the duration that intact female rats maintain lordosis responding during estrus. The present study examined whether VCS could shorten the duration of both appetitive and consummatory measures of female sexual behavior, and whether these effects occur differentially in time and across different hormone priming intervals. Ovariectomized, sexually experienced female rats were administered subcutaneous injections of estradiol benzoate 48 h and progesterone 4 h, before receiving 50 manual VCSs with a lubricated glass rod distributed over 1 h. Control females received sham VCSs distributed over the same time. The females were then tested for sexual behavior in bilevel chambers with two sexually vigorous males (to one ejaculatory series or 10 min with each male, separated by 5 min) 12, 16, and 20 h after VCS. Prior to the final hormone treatment, different groups of females had been given the same hormone treatment either 28, 14, 7, or 4 days before. In females tested at 28- and 14-day hormone intervals, VCS induced both active and passive rejection responses at 12, 16, and 20 h. In contrast, females that received sham VCS displayed relatively normal sexual behavior at 12 h, although by 16 and 20 h these females displayed active and passive rejection. Females tested at 7- or 4-day intervals displayed normal levels of lordosis at all testing times, regardless of VCS treatment. These data indicate that VCS facilitates rejection responses that precede the decrease in lordosis responsiveness. However, the effects of VCS are dependent on the frequency of hormone priming, suggesting that hormone treatment may block some of the long-term inhibitory effects of VCS on female sexual behavior.

Relation of Intromissions to the Female's Postejaculatory Refractory Period in Rats

The objectives of this study were to investigate the temporal aspects of female sexual behavior during single and multiple ejaculatory tests. Females were tested in a two-compartment chamber where they could escape from the male following sexual contacts. In Experiment 1, correlation analysis showed that the number of intromissions received by the female over 3 ejaculatory series was positively correlated with the female's postejaculatory refractory period (PER). In Experiment 2, females receiving 2–4 intromissions before ejaculation had a PER that did not differ from those receiving 5–15 (average 10) intromissions preceding ejaculation. However, if the male ejaculated on the first or second intromission, the female's PER was significantly shorter than the other groups and did not differ from her return latency after an intromission without ejaculation. Females receiving 24–31 intromissions preceding ejaculation exhibited the longest PER. Analysis revealed that the number of intromissions received by females before ejaculation was positively correlated with the female's PER. We concluded that the male's ejaculatory reflex, seminal emission, and postejaculatory behavior alone without at least 2 preceding intromissions were not sufficient to induce a female's PER comparable to that seen after an ejaculation during normal copulation. In addition, the number of intromissions received by the female preceding ejaculation was positively correlated with the female's PER if the range of intromission frequency was large enough.

Effects of paced and non-paced mating stimulation on plasma progesterone, 3 alpha-diol and corticosterone.

In the female rat, gonadal and adrenal progestins and androgens modulate sexual receptivity and in turn, their levels increase in response to mating stimulation. Paced mating, in which the female controls the timing of sexual contacts with the male, is particularly effective at eliciting acute increases in progesterone (P) and 5 alpha-Androstane-3 alpha, 17 beta-diol (3 alpha-Diol). Interestingly, restraint stress produces comparable increases in P and 3 alpha-Diol levels, as well as increases in corticosterone (CORT) levels. In this study, we explored the possibility that paced mating would be associated with increased CORT, in conjunction with mating-induced increases in P and 3 alpha-Diol. Ovariectomized rats primed with estradiol benzoate (10 micrograms in oil SC) and P (0.5 mg in oil s.c.) received a single ejaculatory series from males in paced or non-paced mating tests. Fifteen minutes post-mating rats were exposed to CO2 and rapidly decapitated for the collection of trunk blood and determination of P, 3 alpha-Diol and CORT via radioimmunoassay. As expected, P and 3 alpha-Diol concentrations were significantly elevated in serum obtained from animals allowed to pace their sexual contacts with males compared to those which did not pace their contacts. Importantly, although all mated animals had CORT levels between 10-20 micrograms/dl, there were no differences between paced and non-paced conditions. This suggests that the acute rises in P and 3 alpha-Diol in response to paced mating are not due to paced mating being more stressful than non-paced mating.

Lack of effect of bilateral removal of accessory sex glands on sexual behaviour in the male golden hamster ( Mesocricetus auratus)

In the golden hamster removal of the male accessory sex glands (ASG) may impair fertility because of heavy embryonic wastage. As in the rat, induction of pregnancy and parturition in this species depends on adequate vaginocervical stimulation exerted by the stud at the time of mating. It is possible that embryos fail to develop because of adverse effects on copulatory behaviour consequent upon the absence of accessory sex glands and their associated neural input. The aim of the present study was to test this hypothesis. The results showed that intromission latency, ejaculation latency, intromission frequency, interval of ejaculatory series, postejaculatory pause, ejaculatory frequency and duration of ejaculation were not affected by bilateral section of ampullary glands, coagulating glands, dorsolateral prostate, seminal vesicles, ventral prostate or all of the ASG. It was also concluded that none of the ASG function in the elicitation of sexual behaviour in this species.

Influence of paced mating and number of intromissions on fertility in the laboratory rat

The effects of differential mating stimulation on fertility in rats were examined by mating pro-oestrous females for one ejaculatory series in tests in which they could or could not self-regulate, or pace, the timing of intromissions received by males. Females were autopsied on days 7, 14 or 21 after mating, or on the expected day of birth to confirm pregnancy, and the number of implantation sites or of viable fetuses or pups determined. Because of substantial behavioural variability within an ejaculatory series, data from paced and nonpaced females were divided according to whether they received a low (< or = 8) or high (> or = 9) number of intromissions. The incidence of pregnancy was significantly reduced among paced females receiving few intromissions relative to that of any other group. Histological examination of ovaries from females autopsied on day 7 after mating suggested that the reduced pregnancy rate among this paced, low intromission group resulted from a failure of activation of the corpora lutea, a possible consequence of the low number of intromissions received by these females. However, in paced, low intromission females that became pregnant, litter size was significantly greater than in nonpaced, low intromission females. These results suggest a compensatory effect of the temporal patterning of intromissive stimulation on fertility. This effect is not a consequence of differential mortality after implantation since there was no difference in litter size among females autopsied at any of the four times. The differences between paced and nonpaced females may be attributable to preimplantation effects such as differential release of ova or sperm transport.