Effects of paced coital stimulation on estrus duration in intact cycling rats and ovariectomized and ovariectomized-adrenalectomized hormone-primed rats.

Two experiments, with 121 female Long-Evans rats, investigated sexual behavior in intact cycling Ss and ovariectomized and ovariectomized-adrenalectomized hormone-primed Ss. A partitioned test cage was used in which the female controlled the timing of sexual contacts with males. Females received 9 or 10 intromissions in the partitioned test cage (paced) or with the partition removed (nonpaced), or they received solitary exposure to the test cage or to mounts without intromission with the use of vaginal masks. Intact cycling (Exp I) and gonadectomized hormone-primed (Exp II) Ss displayed similar patterns of contact with males. Exits from and latencies to return to the male compartment increased as the intensity of the antecedent coital stimulation increased. Cycling Ss given experience with paced or nonpaced mating on the evening of proestrus did not exhibit differences in pacing behavior on a 2nd test 17–24 days later. Those receiving paced coital stimulation showed a shorter duration of estrus than did those receiving nonpaced stimulation. Gonadectomized Ss given 3 successive doses of estradiol benzoate (20, 40, and 8 μg/kg, sc) in combination with progesterone (2 mg/kg) did not show shorter periods of estrus than nonpaced or mounts-only Ss. Results suggest that ovarian output in response to paced cervical-vaginal stimulation may contribute to the termination of estrus in the rat. (39 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Conditioned place preference for mating is preserved in rats with pelvic nerve transection.

Female rats exhibit a conditioned place preference (CPP) for a context paired with mating. The present experiment tested the hypothesis that the activation of the pelvic nerve mediates the reinforcing effects of mating for female rats. Rats underwent bilateral pelvic nerve or sham transection and then received paced mating, nonpaced mating, or the control treatment during a CPP procedure. Pelvic nerve transection did not affect the CPP for paced or nonpaced mating. In tests of paced mating behavior, contact-return latencies following intromissions were significantly shorter in rats with pelvic nerve transection than they were in rats with sham transections. These results show that the pathway conveying the reinforcing effects of mating stimulation does not depend on the integrity of the pelvic nerve, but that activation of the pelvic nerve contributes to the display of paced mating behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of ibotenic acid lesions of the nucleus accumbens on paced mating behavior in the female rat.

The present study investigated the role of the nucleus accumbens (NAcc) in paced mating behavior in female rats. A sexually receptive female rat will approach and withdraw from a sexually active male, thereby controlling the timing of the receipt of sexual stimulation (e.g., mounts, intromissions, ejaculations). In this study, ibotenic acid lesions in the NAcc core increased the likelihood that a female rat would withdraw from a male rat after a mount but did not affect contact return latency or sexual receptivity. lbotenic acid lesions in the NAcc shell did not affect paced mating behavior or sexual receptivity. The results suggest that the NAcc core plays a role in suppressing withdrawal behavior in response to less intense mating stimulation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Neurochemical basis of conditioned partner preference in the female rat: I. Disruption by naloxone.

The effects of the opioid antagonist naloxone were examined on the development of conditioned partner preference induced by paced copulation in female rats. In Experiment 1, ovariectomized, hormone-primed rats were conditioned to associate scented and unscented male rats with paced and nonpaced copulation, respectively. Female rats in Experiment 2 associated albino or pigmented male rats with paced or nonpaced copulation. Naloxone or saline was administered before each conditioning trial. During a final drug-free preference test, female rats could choose to copulate with either a pacing related or unrelated male. Saline-trained female rats in the paired group copulated preferentially with the pacing-related male rat, whereas naloxone-trained female rats did not show a preference. The authors concluded that opioids mediated the conditioned partner preference induced by paced copulation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Genitosensory nerve modulation of paced mating behavior: Evidence for pelvic, but not hypogastric, nerve influence.

The pelvic nerve is known to play a role in the behavioral and neurochemical responses exhibited during paced mating behavior. The present study extended the analysis of the contribution of the genitosensory nerves to the display of paced mating behavior to include bilateral hypogastric nerve transection, bilateral pelvic nerve transection, or transection of both the hypogastric and pelvic nerves. Rats with pelvic nerve transection were less likely to exit the male compartment, took longer to exit the male compartment following intromissions, and returned to the male more quickly following intromissions compared to rats with an intact pelvic nerve. In contrast, hypogastric nerve transection alone did not affect paced mating and had no modulating effect on the paced mating behavior of rats with pelvic nerve transection. Our results support the view that key aspects of paced mating behavior are modulated by signals transmitted via the pelvic nerve, without any discernable contribution from the hypogastric nerve. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Perinatal inhibition of aromatization enhances the reward value of sex.

Paced mating reduces the aversive properties and increases the positive characteristics of mating, inducing a reward state. Pacing is able to induce conditioned place preference (CPP), whereas nonpaced mating does not. The authors hypothesized that the aversive properties of mating are caused by androgens from adjacent males or from the mother during fetal life. To test whether aromatization of androgens induces the aversive properties of mating, female rats were treated perinatally with 1,4,6-androstatriene-3, 17-dione (ATD) to inhibit aromatization. When adults, these females were ovariectomized and hormonally primed to evaluate CPP after paced and nonpaced mating. During paced mating, control females showed higher return latencies after ejaculation, whereas ATD-treated females did not show a similar increase. In CPP tests, both paced and nonpaced mating induced a reward state in ATD-treated females, whereas only paced mating induced a reward state in control females. These results show that the perinatal inhibition of aromatization enhances the rewarding properties of mating, suggesting that estradiol induced the aversive properties of mating and/or modified the perinatal organization of the neuronal pathways in females. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dopamine Antagonists Do Not Block Conditioned Place Preference Induced by Paced Mating Behavior in Female Rats.

The authors assessed the behavioral effects of dopamine (DA) receptor antagonists, Cis (Z) flupentixol and S(+)-raclopride L-tartrate, on conditioned place preference (CPP) induced by paced mating behavior. Ovariectomized female rats of the Wistar strain were used. The administration of amphetamine (1 ior. mg/kg) induced a clear CPP that was completely blocked by the DA antagonists flupentixol (0.25 mg/kg) or raclopride (0.125 mg/kg). These doses had no effect on motor coordination. Female rats that mated in a pacing chamber developed a clear CPP. Neither flupentixol nor raclopride blocked the reward state induced by paced mating behavior. These results indicate that DA is not involved in the reward state induced by paced mating behavior in female rats. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Patterns of induction of the immediate-early genes c-fos and egr-1 in the female rat brain following differential amounts of mating stimulation

Vaginocervical stimulation received either during mating or by artificial mechanical means has been shown to induce FOS expression in medial amygdala, preoptic area, hypothalamus, and midbrain of female rats. While mating-induced increases in FOS-like immunoreactivity (FOS-IR) have been shown to require intromissive stimulation from males, the pattern of FOS-IR in animals receiving numbers of intromissions across a range relevant to the induction of the prolactin surges of early pregnancy has not been explored. Experiment 1 examined brain FOS-IR following 15 mounts without intromission or 5, 10, or 15 intromissions in ovariectomized females treated with estrogen and progesterone; these treatments are known to be less than or more than sufficient to trigger prolactin surges in cycling females. FOS was expressed in a graded fashion in the medial amygdala with respect to the numbers of intromissions received and in an all-or-nothing manner in preoptic area, bed nucleus of the stria terminalis, and ventromedial nucleus of the hypothalamus. In experiment 2, 15 intromissions induced expression of another immediate-early gene, egr-1, in each of these same areas as well as in a second division of the bed nucleus of the stria terminalis and in the paraventricular nucleus of the hypothalamus. These studies demonstrate that mating is differentially effective in inducing FOS expression in responsive brain areas and point to the medial amygdala as a site in which summation of intromissive stimulation may occur. Furthermore, the induction of EGR-1 may be a more sensitive marker for mating-induced neural activation in these areas than is FOS.     

Temporal aspects of female musk shrew (Suncus murinus) sexual behavior.

The effects of testing condition on sexual behavior were examined in female musk shrews (Suncus murinus). Females were tested in 2 conditions, a pair test and a paced test. The pair test was similar to traditional sex test conditions in which the female and male are placed into the same chamber together until mating occurs. The paced condition allowed the female to leave the male's chamber and revisit him at will, thus "pacing" the interaction. Females displayed receptivity continuously for 14 days in both conditions. In the paced condition, females were less likely to become receptive within 30 min and mate to ejaculation. However, few additional differences were found between test conditions. Because this is the 1st experiment to use a pacing test paradigm in a species with induced ovulation, the authors speculate that the absence of pacing behavior during mating may be shown by other species that have induced ovulation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Electrophysiological and ultrasonic correlates of reproductive behavior in the male rat.

Monitored the ultrasonic vocalizations of 13 male Long-Evans rats and determined the correlation of these vocalizations with electrophysiological activity measured by chronically implanted hippocampal and cortical electrodes during mating with a female rat. Hippocampal theta rhythms were significantly correlated with high activity, mounting, intromissions, and preejaculatory excitatory behavior and were also significantly associated with 50-kHz short ultrasonic vocalizations. Postmount or postintromission behaviors (grooming, exploration) were closely correlated with an absence of ultrasonic vocalizations and the onset of irregular low-amplitude hippocampal EEG recordings. Long 22-kHz vocalizations occurred during the postejaculatory refractory period. Shorter 22-kHz vocalizations occurred during mating and were associated with unsuccessful intromissions or mounting attempts. Postejaculatory long 22-kHz vocalizations were significantly associated with irregular high-amplitude hippocampal EEG tracings, while preejaculatory short 22-kHz vocalizations were also accompanied by sleeplike irregular high-amplitude hippocampal EEG tracings with cortical spindling. Findings suggest that ultrasonic vocalizations are indicators of the sexual arousal of mating rats. (14 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Learning about sex: Conditioning of partner preference: Theoretical comment on Coria-Avila et al. (2005).

Sexual partner preference in female rats has been difficult to establish experimentally because the vaginocervical stimulation the female receives during the preference test can be rewarding or aversive depending on the context. G. A. Coria-Avila, A. J. Ouimet, P. Pacheco, J. Manzo, and J. G. Pfaus (2005) (see record 2005-06959-008) reported that female rats can be conditioned to show partner preference for a male that is scented with a sexually neutral odor if they are mated repeatedly with that male in a paced mating test. These results suggest that establishment of a partner preference depends on rewarding characteristics of the vaginocervical stimulation the female receives during an initial mating and that selection of a sexual partner can be determined by olfactory stimuli associated with that stimulation. These results are discussed within the context of the appetitive-consummatory construct of sexual behavior and the evolutionary significance of conditioned partner preference. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Female presence during postejaculatory interval facilitates penile erection and 22-kHz vocalization in male rats.

During the postejaculatory interval (PEI), male rats exhibit prolonged immobility, 22-kHz vocalization, and penile erections. To test whether females modulate these behaviors, females were removed after the first or second ejaculation or left in the test chamber. Female presence during the PEI delayed exploratory behavior and facilitated vocalization and erection. Female stimulation of vocalization is consistent with the hypothesis that vocalization has a communicative function, not just a thermoregulatory one. The timing of the effect of females on erection suggests that males are sexually arousable well before they resume copulation. Therefore, erection may be better than vocalization as an indicator of the male's sexual refractoriness. The findings also challenge the conventional view that the PEI comprises absolute and relative sexual refractory periods marked, respectively, by the presence and absence of 22-kHz vocalization. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Naloxone blocks place preference conditioning after paced mating in female rats.

Sexual behavior in male rats induces a positive affect as evaluated by conditioned place preference (CPP). In addition, when females control or "pace" the rate of sexual interaction, a clear CPP is also observed. The reward state induced by mating in male rats is blocked by the injection of the opioid antagonist naloxone. In the present experiment, a dose of 4 mg/kg of naloxone completely blocked the CPP induced in females by paced mating. It appears that a common opioid system is involved in the positive affect induced by sexual behavior in both male and female rats. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Increased extracellular dopamine in the nucleus accumbens and striatum of the female rat during paced copulatory behavior.

Five groups of ovariectomized rats were tested during in vivo microdialysis, and concentrations of dopamine (DA) and its metabolites were determined in dialysate. In striatum, DA increased more in hormone-primed ovariectomized female rats pacing copulation than in those engaging in sex that could not pace, those that were hormone primed but tested without a male present, or oil-treated groups. Administration of estrogen before microdialysis resulted in enhanced striatal DA in response to a male rat relative to the animals tested without a male. Female rats that were pacing sexual behavior also exhibited a greater increase in accumbens DA than did the no-male, estrogen-primed, or oil-treated groups. Nonpacing animals displayed a significant decrease in DA from accumbens 30 min after introduction of the male rat but otherwise were not different from pacing animals. Estrogen-treated animals also had an enhanced increase in accumbens DA compared with oil-treated rats. These data suggest that DA release in the striatum and accumbens is dependent on the context in which sexual behavior occurs and that estrogen may in part modulate these dopaminergic responses. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Responses to copulatory stimulation in neonatally androgenized female rats.

Five experiments evaluated the extent to which copulatory stimulation could ameliorate the anestrus and sterility exhibited by neonatally androgenized female Long-Evans rats (N?=?102). The age at which Ss began to exhibit persistent vaginal estrus and the degree of sexual receptivity exhibited under several testing paradigms were found to be inversely related to the dose of testosterone propionate (TP) injected neonatally. With increasing numbers of mounts received, both the number of androgenized Ss exhibiting sexual receptivity and the quality of the estrous behavior exhibited tended to increase. Ss injected with high doses of TP (500 μg) usually showed little or no receptive behavior even in the most extensive behavioral tests. However, under some testing conditions Ss receiving 50 μg of TP neonatally, while showing little or no receptivity during initial mounts, showed increased receptivity as behavioral tests were extended. Following matings that included 1–5 ejaculations, only control Ss were observed to become pregnant. However, when androgenized females cohabited with males for an extended period, Ss that had neonatally received .5 μg of TP, but not higher doses, did become pregnant. It is concluded that (1) the capacity of systems mediating reproductive physiology and behavior is facilitated by stimuli associated with males; and (2) mating is a characteristic of the female rat, which can be manipulated by injection of hormones during the neonatal period. (13 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Neurochemical basis of conditioned partner preference in the female rat: II. Disruption by flupenthixol.

The effects of the dopamine receptor antagonist flupenthixol were examined on the development of conditioned partner preference induced by paced copulation in female rats. In Experiment 1, ovariectomized, hormone-primed rats were conditioned to associate scented and unscented males with paced and nonpaced copulation, respectively. Females in Experiment 2 associated albino or pigmented males with paced or nonpaced copulation. Flupenthixol or saline was administered before each conditioning trial. During a final drug-free preference test, females could choose to copulate with either a pacing-related or nonpacing-related male. Saline-trained females copulated preferentially with the pacing-related male, whereas flupenthixol disrupted odor but not strain conditioning. The role of dopamine in conditioned partner preference depends on the type of stimuli to be learned. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of pre- and postpubertal social experience on sexual and social behavior in male and female brown lemmings (Lemmus sibiricus).

In 3 studies, male and female brown lemmings were either isolated at weaning (18 days) or then housed with siblings for another 10 days before being isolated. Before testing for sexual behavior at the age of 75–103 days, half of each group of males received a series of exposures to estrous females and half of each group of females was housed with a stud male. The results of mating tests indicate that whereas prior sexual experience facilitated subsequent copulatory behavior in both sexes, prepubertal interactions subsequently facilitated contact social and sexual behavior in males but did not increase the behavioral scores of females, who engaged in high levels of sexual behavior regardless of prepubertal experience. The effect of prior copulatory activity on male sexual performance could not be attributed to increasing age (i.e., maturational processes) because the behavior of males tested once but at different ages did not differ appreciably. Prepubertal social interaction appeared to predispose males to benefit from sexual experience later in life. (35 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hippocampal and cortical activity during sexual behavior in the female rat.

Studied hippocampal and cortical activity during sexual behavior in 6 female albino van Leeuwenhoek-Huis R-strain rats. Hippocampal theta appeared during S's soliciting behavior. High-frequency theta accompanying the male's pursuit slowed when the male mounted the female and then increased in frequency during the brief continuation of lordosis following mounts without vaginal penetration. During prolonged lordosis after intromissions and ejaculations, slow theta continued. No changes in cortical frequencies were observed during mounts, intromissions, or ejaculations. During immobility (standing, sitting, and lying down), hippocampal activity became slow and irregular. High-amplitude hippocampal and, eventually, cortical spindles developed during immobility as sexual exhaustion was approached. Immobility and its accompanying EEG spindling are interpreted as indicative of a sexual satiety or inhibitory process. (21 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effect of coupling interval and pacing cycle length on morphology of paced ventricular complexes. Implications for pace mapping

BACKGROUND: Ventricular pace mapping is performed by comparing the QRS morphology of ventricular paced complexes to that of a template arrhythmia, either a premature ventricular depolarization or a QRS complex during ventricular tachycardia. The objective of this study was to evaluate the effect of coupling interval and pacing cycle length on QRS morphology. METHODS AND RESULTS: The study population consisted of 20 patients (mean age, 38 +/- 16 years) undergoing a clinically indicated electrophysiology procedure. In the first 10 patients, the effect of coupling interval on the morphology of single paced ventricular complexes was evaluated visually and by signal processing techniques. Visually apparent differences in QRS morphology occurred in a mean of 4/12 electrocardiographic leads with a change in coupling interval of > or = 100 ms. In the next 10 patients, the QRS complex morphology during ventricular overdrive pacing at cycle lengths of 600 and 300 ms was found to differ significantly in a mean of 4/12 leads. The QRS morphology during overdrive pacing differed significantly from that of a single paced complex whenever the pacing cycle length differed from the coupling interval of the single paced complex by > 80 ms. CONCLUSIONS: The morphology of single paced QRS complexes may vary, depending on coupling interval, and the QRS morphology during overdrive pacing is affected by the pacing cycle length. During ventricular pace mapping, the coupling interval or cycle length of the template arrhythmia should be matched during pacing. If not, rate-dependent changes in QRS morphology that are independent of the pacing site may confound the results of pace mapping.     

Olfactory Conditioned Partner Preference in the Female Rat.

Paced copulation induces conditioned place preference in female rats. The authors examined whether associating almond-scented males with paced copulation induces conditioned partner preference. The paired group received 4 paced copulations with almond-scented males and 4 nonpaced copulations with unscented males sequentially at 4-day intervals. The unpaired group received the opposite order of association, whereas the randomly paired group received random associations. A 4th group received a single pairing. On the final test, females were placed into an open field with 2 males, 1 scented and 1 unscented. Females in the paired group solicited the scented male more frequently, and most chose the scented male for their 1st ejaculation. Thus, an odor paired with paced copulation elicits conditioned partner preference in female rats. (PsycINFO Database Record (c) 2010 APA, all rights reserved)