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PubMed1997

Subcortical multiple unit activity changes during rat male sexual behavior.

Multiple unit activity (MUA) was recorded from the ventral tegmental area (VTA) and mesencephalic locomotor region (MLR) during copulatory behavior of freely moving male rats. Simultaneous accelerometric recordings of the copulatory pelvic thrusting performed by the male rat were taken to precisely correlate in time the changes in MUA with well defined elements of copulation. The baseline MUA firing rates recorded in the quiet-alert condition in the VTA and in the MLR were significantly increased during pursuit of the female by the male; significantly higher MUA firing rates were found in the VTA at the 500 ms periods before and during the execution of pelvic thrusting in mount, intromission, and ejaculation responses as compared to the baseline, and returned to this value when these responses ended. The maximum MUA firing rate in the MLR was obtained during the execution of pelvic thrusting in each copulatory response, and it remained significantly elevated, as compared to the baseline, after thrusting and at the postintromission and postejaculatory genital grooming, then decreasing to basal values at the initial part of the postejaculatory interval. The fact that the highest changes in MUA were related to pelvic thrusting suggests a major participation of both structures in the execution of motor copulatory responses.

Animals↗
PubMed1997

Female sexual behavior is inhibited by short- and long-term food restriction.

In female musk shrews, sexual receptivity is not restricted to the periovulatory period. Several copulatory bouts that occur over a number of days are required to induce the first ovulation. We tested the hypothesis that food restriction would have a minimal impact on female musk shrew sexual behavior because mating behavior may be uncoupled from ovulation in this species. Three testing conditions were used. In the first study, food-restricted females were maintained at their weaning day weight for 17 days. Food restriction resulted in a significant reduction in the number of females that allowed males to mount, intromit, or ejaculate compared with ad lib-fed controls. In the second experiment, sexually experienced females that were food-restricted for 2 weeks also displayed reduced sexual behavior compared to that in ad lib-fed controls. In the last study, we examined the effects of short-term food fluctuations on sexual behavior. Females food-restricted for 48 h showed reduced mating behavior compared to that in ad lib-fed controls. This was reversed after 24 h of refeeding. These studies show that, even under conditions where copulation does not lead to pregnancy, small reductions in food availability can inhibit female sexual behavior.

Animals↗
PubMed1997

Deafferentation of the olfactory bulbs of male rats reduces erection to remote cues from females.

If male rats are paired with a receptive, soliciting female rat in a setting that prevents physical contact, but permits auditory, visual, and olfactory contact, some will have erections of the penis--noncontact erections (NCE). Surgical deafferentation of the olfactory bulbs from all the known chemosensory systems of the nasal septum renders rats anosmic, decreases sexual performance in copulation tests with females, and substantially reduces the frequency of NCE. Thus, NCE appear to be primarily regulated though the olfactory perception of volatile chemosensory cues from receptive females.

Animals↗
PubMed1997

Patterns of body temperature, activity, and reproductive behavior in a tropical murid rodent, Arvicanthis niloticus.

Nile grass rats (Arvicanthis niloticus), are murid rodents from tropical Africa that exhibit diurnal patterns of wheel-running. In the present paper we describe the temporal organization of several other behaviors in these animals, as well as daily rhythms in their body temperature. In the first experiment, we characterized rhythms of gross motor activity and core body temperature in four adult females implanted with telemetry transmitters and kept on a 12:12 light:dark (LD) cycle. In all animals body temperature and gross motor activity were clearly diurnal, with peaks often occurring around dawn and dusk. In the second experiment we recorded the times of mating and parturition in eight mating couples housed in a 12:12 LD cycle. We monitored animals 24 h a day using a time-lapse video recording system, beginning when males and females were paired, and ending after the birth of the second litter and the associated post-partum copulation. Mating almost always began just before the lights came on, and parturition generally occurred in an "anticrepuscular" pattern, outside of the periods around dawn and dusk. Thus, these animals exhibit an interesting mosaic of temporal adaptations, with some crepuscular tendencies expressed within a predominantly diurnal pattern.

Animals↗
PubMed1999

Effects of naloxone on the acquisition and expression of appetitive and consummatory sexual behavior in male Japanese quail.

Previous studies in Japanese quail indicate that central administration of the opioid antagonist naloxone enhances consummatory sexual behavior (CSB). This effect could be related either to a decrease in sexual satiety or to previously documented stimulatory effects of naloxone on GnRH. The present studies were performed to investigate these two possibilities and to explore for the first time opioid involvement in the expression and acquisition of appetitive aspects of sexual behavior (ASB) in castrated, testosterone-treated Japanese quail. Although no effects on either ASB or CSB were observed in response to peripheral naloxone injections, a significant increase in CSB was observed in males receiving central injections of naloxone. Central injections of naloxone had no effect on the acquisition of a social proximity response used to measure ASB. However, compared to controls a greater number of naloxone-treated birds copulated in the test arena on the first day. Overall, these results indicate an inhibitory role for opioids in CSB, and suggest that opioids are differentially involved in different aspects of sexual behavior.

Analysis of Variance↗
PubMed1999

Vaginocervical stimulation inhibits female-female mounting in laboratory rats.

The objective of this study was to examine how vaginocervical stimulation (VCS) affects female-female mounting in laboratory rats. After receiving sexual stimulation from the male, the latency for the female to mount another female was significantly longer than that of control females. In the absence of any copulatory stimulation, the latency to initiate mounting of another female was about 3 min. However, following three mounts or three intromissions by a male, the latency for the experimental female to initiate mounting increased to about 10 min, and ejaculation abolished mounting for almost 2 h. Once females began mounting, regardless of the copulatory stimulation they received prior to testing, their mounting rate (mounting frequency/2 h) did not differ from stimulus control females. Artificial VCS also inhibited female mounting and anesthetization of the vaginocervical area diminished the inhibiting effect of ejaculation. Taken together, the present results provide evidence that VCS can temporarily inhibit female mounting, and that the duration of the inhibition is related to the amount of VCS received. These data are interpreted within the perspective that female mounting behavior is not a sexual behavior and is consequently suppressed within the context of normal copulation.

Animals↗
PubMed2002

Modulatory activity of sildenafil on copulatory behaviour of both intact and castrated male rats.

The first experiment of the present study investigates the effects induced by sildenafil (1 or 10 mg/kg po) on the copulatory behaviour of intact male rats, categorized, on the basis of seven consecutive mating pretests, as sluggish or normal ejaculators (SE or NE, respectively). The data obtained show that sildenafil modifies both sexual arousal and the ejaculatory mechanisms of copulation, diminishing ejaculation latency in both categories and increasing copulatory efficacy in SE rats; in addition, it reduced the inter-intromission interval in both SE and NE animals and the post-ejaculatory interval only in SE animals. The second experiment, conducted on rats 3 weeks after their castration, shows that sildenafil alone (1 or 10 mg/kg) did not modify copulatory failure. However, 3 months after castration, and 24 h after the last injection of testosterone (25 microg/kg sc) given twice weekly for 4 weeks, sildenafil (1 or 10 mg/kg) ameliorated rat copulatory performance.

Animals↗
PubMed2001

Effect of gonadotrophin dose on oocyte retrieval in superovulated BALB/c mice.

Mice are commonly used animal models in reproductive and developmental research. In order to get satisfying results from such experiments, large numbers of ova must be available and this can be achieved by using various ovulation induction protocols. To obtain an optimal response from these stimulation protocols, parameters such as breeding-housing conditions of the animal strains, the best age for superovulation, and type and dose of gonadotrophins must be optimized. The aim of this study was to investigate the impact of exogenous stimulation with increasing amounts of gonadotrophins on the number and quality of oocytes/pre-embryos recovered from outbred BALB/c mice. A dose-response analysis was performed by stimulating prepubescent (21- to 25-day-old) and sexually mature (6 to 8 weeks old) female mice with hMG, which contains equal amounts of follicle-stimulating hormone (FSH) and luteinizing hormone (LH). The stimulation dose contained 5, 10, 15, 20, 25 or 30 IU of FSH/LH. The effect of increasing stimulation was assessed by monitoring the number and maturity of ova recovered from the tubes. The data were analyzed by using a one-way Anova test and student t-test. Increasing stimulation doses in the prepubescent females resulted in an increased number of ova. A maximum of 55 ova per mouse was reached when stimulating with 20 IU of FSH/LH; higher stimulation doses showed no further increase in oocyte recovery. In the prepubescent group, a maximal number of recovered mature ova was reached with 15 IU of FSH/LH. In the sexually mature female group, 20 IU of FSH/LH gave the best quantitative and qualitative results. Positive effects of copulation on the number and maturity of oocytes in all induction doses were more evident in the prepubescent females and these parameters were significantly more improved (P < 0.05) in this group when compared to the pubertal females. Our findings led to the conclusion that ovulation induction of prepubescent outbred BALB/c mice with 15 IU FSH/LH and sexually mature ones with 20 IU FSH/LH give the best results in terms of oocyte number and maturity.

Animals↗
PubMed1987

Sexual experience and preference for males or females in the female rat.

The influence of sexual experience on preference behavior was investigated in adult female rats. In the first experiment, preference behavior for sexually active males versus estrous females was investigated in female rats who were experienced with mounting behavior. Preference of these mount experienced females was compared to preference of females who were naive in this respect. Mount experience with estrous females induced a female-directed preference in ovariectomized female rats, irrespective of whether the females were treated with OIL or with testosterone-propionate (500 micrograms TP, injected once 48 h prior to testing). Sexually naive, OIL-treated females did not show a preference for males or females, but TP induced a preference for a male. Individual differences in mount frequency were not correlated with preference behavior. In the second experiment, the influence of experience with feminine sexual responses on preference behavior was investigated. OIL-treated and TP-treated females oriented equally toward males and females when they had been given the opportunity to copulate with males prior to the preference tests. The results strongly suggest that prior sexual experience is an important determinant of preference behavior. The female's behavior during sexual interactions was, however, not predictive of later preference.

Animals↗
PubMed1988

Strain differences in the inhibition of infanticide in male mice (Mus musculus).

The mediating mechanisms for the inhibition of infanticide in male mice were examined in two strains of mice. Both copulation and postcopulatory cohabitation inhibited infanticide in CS1 males whereas only postcopulatory cohabitation inhibited infanticide in CBA males. These data illustrate the difficulties of making conclusions concerning infanticide from single studies using single strains or species.

Animals↗
PubMed1989

Induction of copulatory behavior in Aplysia: atrial gland factors mimic the excitatory effects of freshly deposited egg cordons.

Egg laying in the marine mollusc Aplysia is induced and coordinated by peptide products of the egg-laying hormone (ELH) gene expressed in the neuroendocrine bag cells of the central nervous system. At least three structurally related genes, belonging to the ELH family but distinct from the ELH gene, are expressed in the atrial gland, an exocrine organ of unknown function that secretes into the oviduct of Aplysia. The experiments described in this report were designed to test the hypothesis that the atrial gland gene products serve a pheromonal function for the animal, coordinating reproductive behavior among individuals. Our studies showed that there was a significantly shorter latency to copulation when an Aplysia was paired with an animal that was actively laying eggs than when it was paired with a sexually mature but nonlaying animal. Moreover, the addition of extracts or homogenates of the atrial gland to the seawater surrounding two nonlaying animals reduced the latency to mating compared to animals exposed only to seawater or to homogenates of other regions of the reproductive tract, including oviduct. These results suggest that atrial gland products, secreted onto the egg cordon as it passes through the oviduct, may play a pheromonal role and induce mating behavior between individuals. Experiments are in progress to determine whether the active atrial gland factor(s) are products of the ELH-family genes expressed in the gland.

Animals↗
PubMed2001

Exhaustion of the coital reflex in spinal male rats is reversed by the serotonergic agonist 8-OH-DPAT.

Previous studies from our laboratory have shown that the genital motor pattern associated to the coital reflex in spinal male rats becomes exhausted when repeatedly evoked. Exhaustion of the genital motor pattern could be related to the sexual exhaustion phenomenon observed in copulating male rats. The present study was aimed to describe the features of coital reflex exhaustion and to determine if the 5-HT1A agonist 8-OH-DPAT was able to reverse exhaustion of this ejaculatory-like response. Additionally, the effect of pre-treatment with the 5-HT1A antagonist WAY 100635 on the 8-OH-DPAT induced motor response was evaluated. Results revealed that development of coital reflex exhaustion initiated with a progressive increase in the latency of response and was characterised by a change in the properties of the motor pattern itself. Once exhausted, i.v. administration of 8-OH-DPAT provoked the immediate expression of a potent motor pattern similar to the coital reflex, but in the absence of urethral stimulation. Injection of WAY 100635 induced, per se, expression of the coital reflex after exhaustion. Notwithstanding, pre-treatment with WAY 100635 was able to block the 8-OH-DPAT-induced motor response implying that its effect was exerted upon 5-HT1A receptors. Data suggest that the sexual exhaustion phenomenon might possess a spinal component.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed2003

Facilitation of male-like coital behavior in female rats by kindling.

Kindling is a model of epilepsy and brain plasticity. When applied to the medial preoptic area (MPOA) of non-copulating male rats kindling induces masculine sexual behavior. In order to test if kindling could facilitate male-like coital behavior in female rats, sexually naive females were ovariectomized and kindled in the amygdala (AMG) or the MPOA until an intermediate stage (between 1 and 3, MPOA1-3) or until stage 5 (MPOA5 group). Once kindling was established, females were treated with 2.5 mg/Kg of testosterone propionate (TP) for 15 days. Male-like coital behavior was evaluated on days 5, 10 and 15 of treatment. Subjects were then injected with a TP dose of 5 mg/kg for 15 days and tested in the same way as with the lower dose. The number of mounts was significantly increased and the mount latency was significantly reduced in the MPOA1-3 group when tested 5 days after treatment with the low dose of TP. The same facilitation was observed in MPOA1-3 and MPOA5 groups on day 10 of treatment with the low dose of TP. When the animals were under the high dose of TP treatment, the number of intromissions was increased in all experimental groups (including the AMG kindled group) in comparison to sham animals. In a second experiment we evaluated if the facilitation of male-like coital behavior induced by kindling was produced by a modification of the response of the vomeronasal system to sexually relevant cues. Ovariectomized females were stimulated until they reached kindling stage 2, then they were treated with 2.5 mg/kg of TP for 5 days. After animals were exposed for 90 min to clean sawdust or sawdust soiled by estrous females they were perfused. Fos was detected by immunocytochemistry along the vomeronasal pathway. No differences were found in Fos responses between sham and MPOA kindled females. The facilitation of masculine sexual behavior observed in AMG kindled females may be a consequence of the propagation of the AD to other brain regions involved in the expression of masculine sexual behavior. We propose that masculine sexual behavior is facilitated in MPOA kindled female rats by local neural changes produced by this kind of stimulation without modifying the response of the vomeronasal system to sexually relevant cues.

Amygdala↗
PubMed1991

Excitotoxin lesions of the zona incerta/lateral tegmentum continuum: effects on male sexual behavior in rats.

In male rats, ibotenic acid and N-methyl-D-aspartic acid were used to destroy neuronal perikarya intrinsic to an anterior-posterior continuum including the caudal zona incerta and lateral tegmentum. Some lesions virtually eliminated male sexual behavior - an effect most closely associated with damage to the lateral hypothalamus and zona incerta. Many lesioned males who copulated to ejaculation with normally active females showed little or no mating with receptive, but relatively inactive, females. Although it is possible to identify a critical region within the subthalamus whose destruction eliminates male sexual behaviour, sexually-relevant neuronal cell bodies appear to be distributed throughout the lateral hypothalamic/incertal/tegmental continuum.

Animals↗
PubMed1997

Importance of the medial amygdala in rat penile erection evoked by remote stimuli from estrous females.

Effects of medial amygdala lesions (MAL) were examined on rat penile erection in three different experimental situations. Only sexually vigorous males, as identified by preoperative mating tests, were used. Bilateral radiofrequency lesions were confined to the posterior medial amygdala, with little systematic damage to anterior medial amygdala or to adjacent structures. Lesion electrodes were withdrawn without current application in sham-operated animals (SHAM). After recovery for brain surgery, males were tested for (1) noncontact erection (NCE) that occurs when males were placed in proximity to inaccessible estrous females, (2) reflexive erection evoked in supine males by retraction of the penile sheath, and (3) copulatory behaviour with receptive females. In the NCE test, none of the MAL males showed penile erection during the 20 min observation, whereas 70% of the SHAM males showed it (P < 0.001). In contrast, no erectile dysfunction in the MAL males was detected in the other two tests. MAL males displayed more penile-body erections (flips) than SHAM males in the reflexive-erection test (P < 0.05). In the copulation test, most of the MAL males achieved intromission, but their intromission ratio, a partial measure of erectile function, was marginally lower than that of SHAM males (P = 0.051). MAL males had longer intervals between intromissions (P < 0.001); as a result, none of them ejaculated during the 20 min period that followed the first intromission. The results suggest that the posterior medial amygdala plays an essential role in the regulation of NCE, and it may also contribute to the regulation of erection in other contexts.

Amygdala↗
PubMed1999

Testosterone stimulation of the medial preoptic area and medial amygdala in the control of male hamster sexual behavior: redundancy without amplification.

Receptors for gonadal steroids are present in an interconnected network of limbic nuclei. The existence of this network structure has important implications for how steroids control reproductive physiology and behavior. In 1986, Cottingham and Pfaff proposed that properties of a steroid-responsive neural network could include redundancy, amplification, stability and selective filtering. The present study tested the concept of steroid amplification, using male hamster sexual behavior as a model. In the male hamster, the medial amygdaloid nucleus (Me) and medial preoptic area (MPOA) are essential for mating behavior, and both nuclei transduce steroid cues to facilitate copulation. To determine if steroid action at multiple interconnected nuclei amplifies mating, the present study compared sexual behavior in castrated male hamsters bearing unilateral intracranial implants of testosterone in Me or MPOA with that of males with dual testosterone implants in Me and MPOA. Implants that stimulated androgen receptor-containing neurons in Me or MPOA stimulated copulatory behavior above castrate levels. However, behavior of males with dual implants was not significantly different from that of males with single implants. This suggests that steroid action at either MPOA or Me is sufficient to facilitate mating, but dual stimulation of these reciprocally-connected nuclei does not amplify sexual behavior.

Amygdala↗
PubMed2000

Coitus-induced activation of c-fos and gonadotropin-releasing hormone in hypothalamic neurons in female rabbits.

Copulation induces hypothalamic release of neuropeptides and catecholamines, especially gonadotropin-releasing hormone (GnRH) and norepinephrine, in female rabbits. The forebrain distribution of GnRH cells and the cellular events responsible for the coitally induced GnRH surge have not been identified. We characterized the expression of c-fos mRNA before (0 min) and up to 60 min after coitus in forebrain tissues of mated and nonmated females and compared these findings with those in which single- and double-labeled GnRH/Fos protein cells were identified by immunocytochemistry (ICC). Enhanced expression of fos-mRNA occurred 30 min after coitus, especially in the anteroventral periventricular nucleus (AVPV), the encapsulated portion of the bed nucleus of the stria terminalis (BNSTe) and the ventrolateral hypothalamus (VLH); this increased fos-mRNA activity remained elevated at 60 min in the AVPV and VLH, and was reflected by Fos protein expression 90 min postcoitus. Both ICC Fos-labeled and ICC GnRH-labeled cells were widely distributed throughout the forebrain with postcoital increased double-labeling in the preoptic-septal areas, the anterior-medial hypothalamus and the VLH. The increased number of dual-labeled and unchanged number of single-labeled GnRH cells after coitus suggest some GnRH neurons were non-detected before coitus. Many dual-labeled neurons were adjacent to Fos-labeled cells, suggesting enhanced interneuronal input to GnRH cells after coitus. Collectively, the results suggest that coitus activates hypothalamic GnRH neurons via several loci that include the AVPV, BNSTe and VLH. The distinct anatomical location of the AVPV, BNSTe and VLH further suggests that coital signals may reach the hypothalamus via separate neural pathways that are likely developed within the brainstem.

Animals↗
PubMed1986

Feline breeding management.

A comprehensive understanding of behavioral-gonadal-endocrine interrelationships is a prerequisite for the effective management of any feline breeding program. Some of the topics discussed in this article are seasonality of breeding behavior, problems associated with copulation, suggested mating schemes, and pharmacologic control of reproductive cyclicity.

Animals↗