Juvenile play conditions sexual partner preference in adult female rats

Rats can display a conditioned partner preference for individuals that bear an odor previously associated with sexual reward. Herein we tested the possibility that odors associated with the reward induced by social play in prepubescent rats would induce a conditioned partner preference in adulthood. Two groups of 31-day-old, single-housed female rats were formed, and were given daily 30-min periods of social play with scented females. In one group, almond scent was paired with juvenile play during conditioning trials, whereas lemon scent functioned as a novel odor in the final test. The counterbalanced group received the opposite association. At age 42, females were tested for play partner preference with two males, one almond-scented and one lemon-scented. In both groups females displayed a play partner preference only for males scented with the paired odor. They were ovariectomized, hormone-primed, and at age 55 were tested for sexual partner preference with two scented stud males. Females displayed a sexual preference towards males scented with the paired odor as observed with more visits, solicitations, hops and darts, intromissions and ejaculations. These results indicate that olfactory stimuli paired with juvenile play affects later partner choice for play as well as for sex in female rats.     

The role of reinforcement in the sexual behavior of the female rat

In order to clarify the role of reinforcement in the sexual behavior of female rats, females were trained to traverse a runway to achieve contact with incentive males. Females learned to run faster to sexually active males that achieved intromission than to passive males (p<0.05). However, both types of incentive males produced significant learning (p< 0.001). The type of estrus, either natural or hormone-induced, did not affect learning measures. The results were interpreted as requiring that an explanatory model of the female's sexual behavior contain a variable accounting for reinforcement specific to sexual contact as well as for the more general social reinforcement and the well established aversive consequences of mating.     

Sexual behavior in aged, noncycling female rats

Sexual behavior of 19 month old, noncycling, female rats was evaluated for a period of 8 days. The sexual behavior of 11 aged females revealing constant vaginal cornification (CVC) for 30 days prior to, and during the observation period was variable. Eight of the CVC females showed consistently high lordosis quotients (LQ), whereas 3 showed no lordosis. A significant negative correlation was found between food intake and LQ over the 8 day period. In 8 other aged females, the vaginal smear was characterized by a mixture of both leucocytes and cornified cells, each day, for a period of 30 days prior to, and during the observation period. Lordosis behavior was absent in all females revealing this mixed type (MX) smear when they were tested. At random times after the test period, 3 CVC and 2 MX females showed a vaginal cycle. As the vaginal cycle was observed each female was again tested for sexual behavior. All 5 females were highly receptive when placed with the male during the evening of vaginal proestrus, but not at other times. It is concluded that despite disruptions of regular ovarian cyclicity, aged female rats are still capable of showing a lordosis response.     

Olfactory experience and the development of odor preference and vaginal marking in female Syrian hamsters

Rodent reproductive behavior relies heavily on odor processing, and evidence suggests that many odor-guided sexual behaviors are shaped by prior experience. We sought to determine if exposure to male odors during development is required for the adult expression of proceptive sexual behavior toward male odors in female Syrian hamsters. Exposure to male odors was restricted in na?ve subjects by removing all male siblings from the litter at three to five days of age. Control litters were also culled, but included equal numbers of male and female pups. As adults, na?ve females displayed investigatory preferences toward male odors in a Y-maze that were comparable to control females; this preference was observed whether contact with the odor stimuli was prevented of allowed. In contrast, na?ve females vaginal scent-marked equally toward male and female volatile odors, suggesting an inability to target behavior toward sexually relevant odors. However, na?ve females marked preferentially toward male odors when allowed to contact the odor stimuli. These results provide evidence for the experience-dependent development of vaginal marking behavior toward volatile components of sexual odors. Furthermore, they suggest that distinct mechanisms regulate the development of odor preferences and vaginal marking behavior in this species.     

Sexual arousal of the female hamster

Elicitation of the lordosis response, using a manual stimulation technique, was facilitated by contact with an anaesthetized male hamster. Exposure to an intact anaesthetized male decreased latency to lordosis and increased lordosis duration. Exposure to a gonadectomized anaesthetized hamster significantly reduced the latency to lordosis, but did not affect lordosis duration.     

Sexual preference in female rats during estrous cycle, pregnancy and lactation.

Choice of a male or female social contact was studied in intact female rats in a runway-choice apparatus during estrous cycle, pregnancy, and lactation. The male was chosen significantly more often during proestrus/estrus than during the diestrous days of the cycle. During pregnancy this preference in choice declined only to reappear gradually during the lactation period. The shifts in the level of motivation to seek out the male support previous studies and point to the significance of estrogen in producing the preference for the male.     

Exposure to PCB 77 affects partner preference but not sexual behavior in the female rat

In rats, exposure to the polychlorinated biphenyl congener 3, 4, 3′, 4′-tetrachlorobiphenyl (PCB 77) affects the brain and behavior of the offspring as well as the maternal behavior of the dams. In the present study, a cross-fostering design was used to examine the effects of pre- and/or postnatal exposure to PCB 77 on sexual behavior and partner preference in female rats, and to determine the role of altered maternal behavior in the mediation of these effects. Pregnant rats were treated with oil or PCB dissolved in oil (2 mg/kg b.w.) on gestation days 6-18 and then given pups that had been exposed to either the oil vehicle or PCB during gestation. As adults, the female offspring were tested for partner preference (that is, whether they preferred to spend time with a sexually receptive female or a sexually active male) and sexual behavior. None of the treatments affected female sexual behavior. However, both double exposure and postnatal exposure diminished the animals' preference for a male over a female stimulus, but partner preference was not affected by prenatal exposure alone. There were no significant correlations between the changes in partner preferences due to PCB exposure and the amount of maternal grooming and licking received by the treated litters. Thus, female partner preference is affected by early PCB exposure, and the effects depend upon whether the exposure is in utero or via lactation and may be independent of any effects of the PCB on maternal care.     

Effects of neonatal castration and testosterone treatment on sexual partner preference in the ferret

Groups of male and female ferrets were tested in a T maze to determine whether they preferred to approach and interact with a sexually active male or an estrous female. Control male and female ferrets gonadectomized (GX) on postnatal Day 35 and tested in adulthood while receiving no hormone or testosterone (T) displayed no significant preference. When given estradiol benzoate (EB), however, control males preferred stimulus females whereas control females preferred stimulus males. When tested in adulthood with EB treatment, males GX on postnatal Day 5 showed a significant reduction in their approach to stimulus females, although they did not switch their preference to stimulus males and thereby resemble control females. Female ferrets GX on postnatal Day 5 and given a high dosage of T over postnatal Days 5–20 showed a significant reduction in their approach to stimulus males, although they did not switch their preference to stimulus females, and thereby resemble control males. The results suggest that extended perinatal exposure of male ferrets to T is required for the development of a sociosexual preference for females.     

Sex responses of the female hamster: Effects on male performance

During copulation the female hamster adjusts the position of the perineal region in response to tactile stimulation from the male. Anaesthetization of the perineal region of the female eliminates these adjustment responses and reduces the probability that the male will ejaculate in a five-minute mating test. Anaesthetization also increases the variability of male performance. However, sexually aroused males were not affected.     

Partner preference: Assessing the role of the female goat

For domestic ruminants, the male is thought to have the control over mate choice. The aim of this study was to assess the potential role the female goat plays in choosing a sexual partner. Approach frequency and proximity time to various social or sexual stimuli in a Y-maze apparatus were used as partner preference assessment parameters. Ovariectomized females were either induced into estrus (n = 8) or induced into anestrus (n = 8) and exposed to various goal stimuli — intact unfamiliar females (estrous and diestrous), intact males, and neutral (empty) in six separate trials. Total arm entries and time spent within one body length of the goal (proximity time — used to calculate preference scores) were recorded for subjects. With a male present, anestrous subjects had significantly more total arm entries than estrous subjects. Estrous subjects showed a significant preference for the male goal (M) versus the estrous female (ES), diestrous female (DS), and empty goals, respectively. Estrous subjects also showed a preference for the ES and DS goals when one goal was left empty. Anestrous subjects showed a preference for the goal containing ES, DS, and M compared to empty goals. They also showed a preference for ES vs. DS. The Y-maze is a tool that can be used to assess sexual and social partner preferences in female goats. The role the female plays in choosing a partner may be much greater than previously considered.     

Reduction of genital sensory input and sexual behavior of female guinea pigs

The role of the pelvic, pudendal and genitofemoral nerves in governing the display of lordosis and in determining the duration of estrus was examined in the female guinea pig. The effect of transection of these nerves was to increase the amount of time lordosis was held during intromission as reflected by increased time from the first intromissive thrust to termination of lordosis and increased thrusts per intromission by the male. Although lordosis was held for a longer time, lordosis was terminated by neurectomized females before the male broke contact with the female, as is the case with intact female guinea pig. Abbreviation of the duration of estrus as a result of mating was not prevented by transection of the pelvic, pudendal, and genitofemoral nerves. The results suggest that sensory input transmitted via the pelvic, pudendal and genitofemoral nerves is capable of molding the character of the lordosis response of the female guinea pig, but is not responsible for the inhibition of the display of lordosis following copulation.     

Limited coital stimulation facilitates sexual responses of the female hamster

The results of two separate experiments indicate that limited sexual stimulation (six intromissions) increases both the lateral extent of the region on the perineum from which pelvic adjustment responses can be elicited by tactile stimulation and the magnitude of the responses elicited. Response magnitude was affected by the intensity and pattern of stimulation and varied significantly among individuals. Possible mechanisms for these sex responses are discussed in relation to the results of neurophysiological investigations of potentially similar processes in the rat [10].     

Nuclear estrogen receptor binding in microdissected brain regions of female rats during pregnancy: Implications for maternal and sexual behavior

Previously, we showed that changes in nuclear estrogen receptor (NER) concentrations within large dissections of the preoptic area and hypothalamus of pregnant rats might underlie changes in both maternal and sexual behaviors. To more precisely localize these biochemical changes, NER concentrations were measured in microdissected nuclei within the preoptic area and hypothalamus of pregnant rats on days 8, 16 and 22. Results indicated that NER levels changed significantly throughout pregnancy and that the magnitude and direction of change was site specific. Although a different pattern of change was found in each nucleus, NER levels in most preoptic area nuclei were significantly higher by the 16th day of pregnancy compared to those on day 8, while receptor levels in most hypothalamic nuclei did not increase until day 22 of pregnancy. The higher NER levels found in preoptic area nuclei of female rats as pregnancy advances can be correlated with growing maternal responsiveness during pregnancy, while elevated concentrations of NER in hypothalamic nuclei at the end of pregnancy may indicate preparation for postpartum estrus.     

The role of vaginal stimulation for the acquisition of conditioned place preference in female Syrian hamsters

This study investigated the importance of vaginal stimulation on conditioned place preference by sexual behavior in female Syrian hamsters. Hormonally primed female hamsters given vaginal masks and topical lidocaine prior to conditioning sessions were no different in their place preference conditioning compared to female controls with no vaginal mask or lidocaine. Control females not provided a sexually active male did not show any preference for either compartment of the conditioning apparatus. These results suggest that stimuli, in addition to vaginal stimulation, are effective in producing a place preference during the mating experience in female hamsters.     

Midbrain lesions eliminate sexual receptivity but spare sexual motivation in female rats

To measure sexual motivation we have used a preference test paradigm which involves testing a female with a sexually active male and a sexually inactive castrate male at the same time. On the assumption that a sexually motivated female will choose to spend more time with a partner who can provide her with stimulation appropriate to her motivational state, a female can be said to be sexually motivated to the extent that she spends more time with the active male than with the castrate. We find that bilateral destruction of the midbrain peripeduncular region eliminates the lordosis reflex in female rats, and abolishes sexual soliciting darting responses. Lesioned females treated with ovarian hormones continue, however, to show a strong preference for a sexually active male over a castrate. Thus, although peripeduncular destruction eliminates copulatory behavior, such destruction appears to spare hormone dependent systems for sexual motivation.     

Effects of prenatal stress on sexual partner preference in mice

Three-month old, male Swiss Webster mice were born to either control dams or dams who had been prenatally stressed with light, heat, noise and handling during the last week of gestation. As adults, male offspring were tested on sexual partner preference and sexual behavior (mounting, intromissions and lordosis) with a sexually experienced male stimulus animal and a stimulus estrous female. In comparison to males born to control dams, prenatally stressed males showed a sexual partner preference for the sexually active male as demonstrated by a negative partner preference score, more and longer visits to the male's compartment, fewer and shorter visits to the female's compartment and longer latencies to and lower frequencies of mounts and intromissions of females. In addition, stressed males showed a greater frequency of lordosis and a higher lordosis quotient than did control males. This study is the first to investigate the effects of prenatal stress alone, without hormonal manipulation, on sexual partner preference using both a partner preference paradigm and measures of sexual behavior such as mounting, intromissions and lordosis. These findings support the suggestion that prenatal stress alone is enough to significantly affect sexual partner preference in male mice.     

Stimulus animal characteristics do not modulate the expression of partner preference by female rats

The stimulus animals used in tests of partner preference in female rats vary. To test the hypothesis that the alternative stimulus animal modulates the preference for an intact male, gonadectomized (GDX) female rats received estradiol benzoate plus progesterone or the oil vehicle and were tested for partner preference with either an intact male paired with a GDX hormone-primed female or an intact male paired with a GDX male. Rats were tested under conditions that limited physical contact (No Contact) or allowed sexual interaction (Contact). Stimulus animal condition was not a primary determinant of partner preference. In contrast, contact condition and hormone treatment modulated preference, as well as activity levels and the display of proceptive behaviors. Our findings demonstrate that the characteristics of the alternative stimulus animals tested here do not play a significant role in modulating partner preference in female rats.     

Characteristics of sleep following sexual activity and wheel running in male rats

The EEG sleep patterns of 12 male rats were studied for 4 hr following each of three different conditions: sexual activity, wheel running and no manipulation. Sexual activity was followed by substantial increases in sleep as indicated by several measures. Wheel running produced some enhancement of sleep, but significantly less than did sexual activity. Sleep following sexual activity generally was characterized by fewer, relatively long episodes, whereas that following wheel running was characterized by more short episodes.     

Postpartum copulation and induction of pregnancy in roof rats (Rattus rattus)

Two groups of 10 female roof rats were mated either in cycling or postpartum estrus to provide a quantitative comparison of copulatory behavior and to compare the stimulus requirements for the initiation of pregnancy. Animals in both estrous conditions were mated to one ejaculation, three ejaculations and to sexual satiety in repeated tests. The results indicate there were no differences between estrous conditions in the qualitative patterns of copulation but that males achieved more intromissions in the first series of postpartum tests than in cycling estrous tests. The stimulus requirements for pregnancy initiation were not found to vary as a function of estrous condition, however it was found that postpartum matings resulted in more pups per litter than did cycling estrous matings. The results were discussed with regard to the functional significance of species differences in copulatory behavior and in stimulus requirements for pregnancy.     

Re-feeding and the restoration of odor attractivity, odor preference, and sexual receptivity in food-deprived female meadow voles

Food-deprived meadow voles were used to test predictions of two hypotheses associated with the recovery of sexual behaviors following re-feeding. Specifically, we tested between the body weight set point and metabolic fuels hypotheses. To do so, we determined whether the body weight of previously food-deprived female voles had to return to pre-food deprivation levels before they would recover their sexual behaviors. The body weight set point hypothesis predicts that food-deprived females that were re-fed will recover their sexual behavior after they return to their original body weight. In contrast, the metabolic fuels hypothesis predicts that food-deprived females that were re-fed will recover their sexual behavior before they return to their original body weight. That is, when the females are in positive energy balance. To distinguish between these two hypotheses, female voles were food deprived for 24 h, which is sufficient to inhibit all three components of sexual behavior. The food-deprived females were then supplied ad libitum food for 0 h, 24 h, 48 h, 72 h, or 96 h and weighed. Females were then tested for their sexual behaviors (odor attractivity, odor preference or proceptivity, sexual receptivity). Re-feeding for 48 h was sufficient to restore odor attractivity, 72 h was sufficient to restore odor preferences for opposite sex conspecific odors, and 96 h was sufficient to restore sexual receptivity to those similar to that of females that were not food deprived. The time-points that the behaviors were recovered were prior to voles recovering their initial body weight. Thus, the data support the metabolic fuels hypothesis.