Conditioned Partner Preference Research Articles

Conditioned partner preference in male and female rats for a somatosensory cue.

Male and female rats form a conditioned preference to copulate and/or mate with conspecifics bearing an odor that was paired with either the postejaculatory reward state in males, or paced sexual contact in females, making the odor act as a discrete partner-related cue. Here, we asked whether a somatosensory cue, a rodent jacket, could act as a discrete cue to establish a conditioned partner choice (CPC). In the first study, sexually naïve Long-Evans males and females underwent 14 copulatory conditioning trials for 30 min with their opposite sex partner in unilevel pacing chambers. On the final test, each experimental male or female was placed into an open field with two sexually receptive partners, one jacketed and the other unjacketed. A trend was found for more males to ejaculate first with jacketed females relative to the unjacketed females, whereas the females had no preference. Males and females in the second study were exposed sequentially to jacketed, sexually receptive partners, and unjacketed, sexually nonreceptive partners prior to a final open field test. Both males and females displayed a significant CPC for the jacketed opposite sex partner. This study demonstrates that a somatosensory cue previously used to establish sexual arousal as a contextual cue on rats can be used as a discrete, partner-based cue to establish a CPC for a particular partner wearing the jacket and that stronger conditioning occurs when the jacket is explicitly paired with the sexual reward state. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Cohabitation between male rats after ejaculation: Effects on conditioned partner preference

Male rats display a conditioned ejaculatory preference for females that bear olfactory cues associated with ejaculation+the postejaculatory interval (PEI), or with the PEI alone. This indicates that exposure to a partner during the PEI is necessary and sufficient 'for the development of conditioned sexual partner preference. In the present study we examined the effect of cohabitation between two males during the PEI on the possible development of same-sex partner preference. Males first copulated with an ovariectomized, E+P primed female to one ejaculation and were immediately removed from the female's chamber and placed in another chamber with a conspecific male scented with almond odor as a conditioned stimulus (CS+). Cohabitation lasted for 1h and started immediately after ejaculation in the PEI group and 7h later in the control group. Conditioning occurred daily for a total of ten trials with different females, but cohabitation during the PEI occurred always with the same stimulus male partner. On trial 11, males were tested for social partner preference with two stimulus male partners. One was the familiar scented male and the other an unfamiliar unscented male. Results indicated that males did not develop any social or sexual preference for the male associated with the PEI. In fact, rats from the PEI group interacted significantly less with the scented male as compared to the unscented male, and displayed more agonistic behaviors towards the scented male than towards the unscented male. These data show that conditioned same-sex preference does not develop as a result of cohabitation during the PEI. We discuss the implications for conditioned hostility in intrasexual competition.

Sexual experience blocks the ability of clitoral stimulation to induce a conditioned place preference in the rat

We have previously established the rewarding value of clitoral stimulation (CLS) through the demonstration that manual, distributed, CLS induces a significant conditioned place preference (CPP) and conditioned partner preference in naïve, hormonally primed and non-hormonally primed rats. The present experiment asks whether previous sexual experience might inhibit the ability of clitoral stimulation to induce a conditioned place preference.Female Long–Evans rats were ovariectomized and treated with 10μg of estradiol benzoate (EB) 48h and 500μg of progesterone (P) 4h prior to receiving either 0, 1, or 5 consecutive copulatory sessions with a sexually vigorous male. Each copulatory session ended when females received at least 1 ejaculation. Females then experienced 10 alternating trials of distributed CLS or no CLS paired with one side of a non-biased CPP box under the same hormone-priming regimen. Females that experienced 5 consecutive copulatory sessions did not develop a significant place preference indicated by both a preference score (the proportion of time spent in the reinforced chamber) and a difference score (time in the non-reinforced chamber minus the time in the reinforced chamber) compared prior to and following the 10 conditioning trials. This suggests that repeated copulatory experience might induce a desensitization of the genitosensory circuit since copulation includes both clitoral, and vaginocervical stimulation from mounts plus intromissions. Alternatively, repeated sexual experience prior to conditioning may generate a UCS pre-exposure effect that cannot be altered when manual clitoral stimulation is paired with a new environment.

Ethanol-induced conditioned partner preference in female mice

Drinking behavior and social context are intimately intertwined. Peer relations can promote drinking. Conversely, alcohol promotes social interaction. The present study tested female mice for ethanol-induced conditioned partner preference. Ovariectomized (OVX) C57Bl/6 females with chronic estradiol replacement (OVX+E) received saline or ethanol (1, 2 or 4g/kg) ip and were paired 4× for 30min each with 1 of 2 stimulus females. The test female was paired with the CS− stimulus female following saline, and was paired with the CS+ female following ethanol. After pairing, we measured proximity of the test female to the CS+ and CS− females in a 10’ test. In a second study, OVX and OVX+E females were tested for conditioned partner preference (CS+ vs. CS−) in response to 2.5g/kg ethanol. In separate groups of mice, both test and stimulus females (IS+) received ethanol during pairing to determine if test mice develop conditioned partner preference for another intoxicated mouse. OVX+E test females showed conditioned partner preference for the CS+ female in response to ethanol at 2g/kg (change in preference score for CS+: +86.6±30.0s/10min), but not at 0, 1 or 4g/kg. At 2.5g/kg ethanol, OVX+E females developed conditioned partner preference for either IS+ (+63.6±24.0s) or CS+ females (+93.8±27.1s). OVX test females demonstrated ethanol-induced conditioned partner preference only for the IS+ female (+153.8±32.0s). These data demonstrate that ethanol promotes social preference in female mice, and that estradiol enhances this effect.

Tickling in juvenile but not adult female rats conditions sexual partner preference

Female rats display a conditioned partner preference for males that bear odors paired with different types of rewarding unconditioned stimuli (UCS). Here we examined whether tickling constitutes a rewarding UCS that supports the development of partner preferences. In Experiment 1, we tested the possibility that odors associated with a tickling UCS in prepubescent rats would induce a conditioned partner preference in adulthood. Two groups were formed with 31-day-old, single-housed females, tickled for 6min daily for 10days, by a hand that wore a scented glove (almond or lemon). At 47days of age, females were ovariectomized (OVX), hormone-primed (EB+P), and tested for sexual partner preference with two scented stud males (one almond and one lemon). In each group, females displayed a sexual preference toward males bearing the odor paired with tickling, as observed with longer visits, more solicitations, hops & darts, and receiving more intromissions and ejaculations from the preferred male. In Experiment 2, we used 3-month old, OVX, hormone-primed rats conditioned every 4days for 10 trials. In contrast to juvenile females, adult females failed to prefer males that bore the odor paired with tickling but instead preferred the novel male. These results suggest that tickling has opposite age-dependent effects in the conditioning of partner preference. Tickling in juvenile females appears to act as a rewarding UCS, whereas in adult females it may act as an aversive UCS. Further research is needed to understand brain mechanisms that might account for such differences.

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.

Same-sex cohabitation under the effects of quinpirole induces a conditioned socio-sexual partner preference in males, but not in female rats

The effects of the dopamine D2-type receptor agonist quinpirole (QNP) were examined on the development of conditioned same-sex partner preference induced by cohabitation in rats. In Experiment 1, males received either saline or QNP (1.25mg/kg) and cohabited during three trials with almond-scented stimulus males that were sexually naïve. In Experiment 2, males received six trials, and in Experiment 3 received three trials with sexually expert stimulus males. During a final drug-free preference test, males chose between the familiar or a novel male partner. In Experiments 1, 2 and 3 only QNP-treated males displayed a social preference for the familiar male, observed with more time spent together. In Experiment 3 males also displayed a sexual preference observed with more non-contact erections when were exposed to their male partner. In Experiment 4 we tested the effects on OVX, E+P primed females that received 1 systemic injection of either saline or QNP during three conditioning trials. In Experiment 5, females received 2 injections 12-h apart during each trial. Results indicated that both saline and QNP-treated females failed to develop partner preference. These data demonstrate that enhanced D2-type receptor activity during cohabitation facilitates the development of conditioned same-sex partner preference in males, but not in female rats. We discuss the implications for same-sex partner preferences.

Context alters the ability of clitoral stimulation to induce a sexually-conditioned partner preference in the rat

We have shown previously that clitoral stimulation (CLS) of female rats induces significant conditioned place preference (CPP), indicating that it is rewarding. The present study asked whether CLS could induce a conditioned partner preference. In the first experiment, sexually naïve females received 10 alternating trials of CLS and No-CLS in the presence of a male rat behind a wire-mesh screen. For one group, CLS was made in the presence of the male scented with almond extract. On alternating trials, those females received sham CLS in the presence of an unscented male behind the screen. The order was reversed for the other group. After 5 trials in each condition, females were placed into an open field with two sexually vigorous males, one scented and the other unscented. Contrary to expectation, females displayed a preference for the male associated with sham CLS. The second experiment examined whether a partner preference could be conditioned by associating CLS with the almond odor alone. A new group of sexually naive females received the same CLS-odor, No-CLS-No Odor pairings as above, but with the odor presented on cotton gauze in the chamber. During the final open field test, those females selectively solicited the scented male. We conclude that CLS that induces CPP also induces conditioned partner preference. However, we propose that CLS in the presence of an inaccessible male created a sexual inhibitory state for female rats.

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.

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.

Neuronal activation by stimuli that predict sexual reward in female rats

Conditioned stimuli (CSs) associated with paced copulation induce a conditioned partner preference for males bearing the CS. Here we examined the activation of Fos immunoreactivity (Fos-IR) following exposure to a CS previously paired with either paced or nonpaced copulation. Ovariectomized, hormone-primed rats received 10 sequential conditioning trials at 4-day intervals. In experiment 1, females in the odor-paired group learned to associate an almond odor on a male with paced copulation and an unscented male with nonpaced copulation. In the odor-unpaired group, females received the opposite association. In experiment 2, females associated two different strains of male, Long-Evans or Wistar, with paced or nonpaced copulation, respectively. A preference test indicated that females in both experiments developed a conditioned preference for the pacing-related males, as indicated by significantly more solicitations toward the male and a preference to copulate with the pacing-related male. Subsequently, females were exposed to the CS (odor or strain) alone for 1 h prior to kill and preparation of their brains for immunocytochemistry. In both experiments, the CS associated with paced copulation produced significantly more Fos-IR in the piriform cortex, medial preoptic area, and ventral tegmental area, relative to the same odor or strain cues associated with nonpaced copulation. These findings provide evidence that the state associated with paced copulation can be conditioned to environmental stimuli such as neutral odors or strain cues, which earn an incentive value via classical conditioning. The significance of the brain areas activated is discussed with regard to their role in sexual and other motivated behaviors.

Fecal bulking in a frequently mated female rat

One month into a study examining the effects of flupenthixol on sexual behavior and con-ditioned partner preference, we noticed that one female Long-Evans rat started to lose weight. The animal was one of forty 200–250 g Long-Evans rats housed in groups of four in wire-bottomed mesh cage. Each rat had free access to laboratory-rat pelleted feed and water. The animal room was maintained at 21 ± 2˚ C and 30–80% humidity on a reverse 12:12-h light/dark cycle.Half the rats in the study received intra-peritoneal (i.p.) injections of 0.25 mg/kg every four days, 30 minutes before they engaged in sexual behavior. The other half received 1 ml/kg of 0.9% saline and served as a control group. The affected rat was in the flupenthixol treatment group, and the technician responsible for administering the IP injections reported the presence of a hard mass in the rat’s abdominal cavity. We examined the rat; palpation of the abdominal cavity indicated the presence of a firm fecal mass distending the colon. On neurologic examination the rat dis-played normal postural reactions, spinal reflexes, and nociception. Its gait, however, was slightly abnormal, but because flupen-thixol is a dopamine antagonist, we consid-ered the uncharacteristic movement to be a consequence of altered motor activity

Conditioned partner preference in female rats for strain of male

Female rats show conditioned place preference following paced copulation, and we have recently demonstrated that pairing almond odor with paced copulation induces a conditioned partner preference for almond-scented males. The present study examined whether cues of two different strains of male (albino and pigmented) induce a conditioned partner preference for the strain of male associated with paced copulation. Ovariectomized, hormone-primed Wistar (W) or Long-Evans (LE) female rats received 10 conditioning trials at 4-day intervals. In the Wistar-pacing group females copulated with W males in a chamber bisected by a 4-hole partition that only the female could pass through. Four days later, they copulated with LE males without the partition. The Long-Evans-pacing group received the opposite association. In the final preference test all females chose freely between two males tethered in opposite corners of an open field, one W and one LE. Regardless the strain of male, females displayed more solicitations toward the pacing-related male, and most of the females received their first ejaculation from that male. The preference was facilitated if the pacing-related male was of the same strain as the female. These results suggest that female rats have an unconditioned preference for males of the same strain, but this preference can be switched towards males of a different strain if that male is associated with the sexual reward induced by paced copulation.

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.

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) 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.

The neurobiology of pair bonding.

A neurobiological model for pair-bond formation has emerged from studies in monogamous rodents. The neuropeptides oxytocin and vasopressin contribute to the processing of social cues necessary for individual recognition. Mesolimbic dopamine is involved in reinforcement and reward learning. Concurrent activation of neuropeptide and dopamine receptors in the reward centers of the brain during mating results in a conditioned partner preference, observed as a pair bond. Differential regulation of neuropeptide receptor expression may explain species differences in the ability to form pair bonds. These and other studies discussed here have intriguing implications for the neurobiology of social attachment in our own species.