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)     

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)     

Naloxone, but not flupenthixol, disrupts the development of conditioned ejaculatory preference in the male rat.

Male rats display a conditioned preference to ejaculate with a female bearing an odor paired previously with copulation to ejaculation. The present study examined the role of endogenous opioid and dopamine systems in this preference. Male rats received saline, the opioid receptor antagonist naloxone, or the dopamine receptor antagonist flupenthixol prior to 10 conditioning trials in a pacing chamber with an almond-scented female. On the final test, all males were injected with saline and given access to 2 females, 1 scented and the other unscented, in an open field. Only males injected with naloxone during training failed to manifest a conditioned ejaculatory preference. These findings suggest that activation of opioid, but not dopamine, systems during sexual interaction are necessary for conditioned ejaculatory preference in male rats. (PsycINFO Database Record (c) 2010 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)     

Differences in the sexual conditioned behavior of male and female Japanese quail (Coturnix japonica).

The conditioned responses of male and female Japanese quail (Coturnix japonica) were compared in a Pavlovian conditioning procedure in which presentation of a brief conditioned stimulus was immediately followed by the release of a copulation partner. Male quail vigorously approached the conditioned stimulus and were much more likely to enter the compartment housing their copulation partner than were female birds (Experiment 1). In females, sexual conditioning resulted in increased squatting (Experiment 2). This response was the reflection of sexual behavior rather than more general social behavior (Experiment 3). These findings provide the first definitive evidence of sexual learning in female quail and are consistent with the interpretation that sexual conditioning increases sexual arousal or receptivity in both sexes but the increase has different behavioral manifestations in male and female quail. (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)     

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)     

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)     

Role of olfactory stimuli during copulation in male and female rats.

Describes 3 experiments with a total of 74 gonadally-normal male and 29 ovariectomized female Long-Evans rats. Male and female reactions toward odors from novel and original partners were observed prior to the male's attaining his 1st or 2nd ejaculation. The male's reaction depended upon the sexual condition of the female. Only prior to their initial ejaculation did the males prefer their original partner's odors to those of novel females and only if the odors were collected from the females prior to copulation. This finding corresponded with observations of the male's random choice of partner during copulation. Females responded nonpreferentially if they had copulated prior to testing and showed a marked decrease in responsiveness as copulation continued. Prior to copulation females preferred the odors from males which had not copulated to those of males which had. (25 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sexual behavior regulated (paced) by the female induces conditioned place preference.

The possibility that female-paced coital behavior induces a reward state of sufficient intensity and duration to induce conditioning was evaluated by the conditioned-place-preference paradigm. Ovariectomized female rats, treated with estradiol benzoate and progesterone, regulated (paced) their coital interactions with a stud male through a 2-compartment chamber in which only the female could freely move from one compartment to the other. The females that paced their coital interactions showed a clear place preference. In contrast, no change in preference was observed in the females that could not pace their coital contacts. The change in preference in the females that paced their coital interactions was similar to that produced by an injection of morphine (1 mg/kg). These results suggest that coital interactions in females can induce a reward state when the females can control the pace of the sexual interaction. (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)     

Hormonal regulation of adult partner perference behavior in neonatally ATD-treated male rats.

Male rats, neonatally treated with ATD (1,4,6-androstatriene-3,17-dione), which blocks the aromatization of testosterone into estradiol (E?), were tested for adult partner preference behavior (PPB; estrous female vs active male). Castration caused a decrease in preference for the female partner in all males, with ATD males showing lower preference for the female partner than controls. Long-term castrated males did not show preference for either partner. Precastration levels of PPB in control males occurred after treatment with E? or dihydrotestosterone (DHT) plus E?. DHT alone had no effect on PPB. With E? alone, the ATD males clearly preferred the male partner. When DHT was added, these ATD males showed no preference for either partner or a low preference for the female partner. In conclusion, adult PPB in male rats is activated by endogenous testosterone or by both its metabolites (DHT and E?) or by E? alone. ATD males showed a much lower preference for the female. There was a differential effect of DHT and E?: DHT had no effect, but E? clearly caused ATD to prefer the male partner and control males to prefer the female partner. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Olfactory conditioning of sexual behavior in the male rat (Rattus norvegicus).

The role of classical conditioning in the copulatory preferences of male Long-Evans rats (Rattus norvegicus) was examined by pairing a neutral olfactory stimulus (almond odor) with female reproductive status. During training trials, the males were given access to scented or unscented females that were either sexually receptive or unreceptive. Subsequently, copulatory preferences were tested in males given simultaneous access to 2 receptive females, 1 scented and 1 not. Males trained with scented-receptive females displayed an ejaculatory preference for the scented female. Males trained with scented-unreceptive females or with unscented-receptive females displayed an ejaculatory preference for the unscented female. Males displayed no preference when scent and reproductive status were paired randomly. These results demonstrate that classical conditioning produces an ejaculatory preference. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A Nitric Oxide Synthesis Inhibitor in the Medial Preoptic Area Inhibits Copulation and Stimulus Sensitization in Male Rats.

Dopamine in the medial preoptic area (MPOA) facilitates copulation in male rats, and nitric oxide (NO) regulates basal and female-stimulated MPOA dopamine release. Microinjection of L-nitro-arginine methyl ester (L-NAME, an NO synthesis inhibitor) into the MPOA blocked copulation in naive rats and impaired copulation in sexually experienced males. In other naive rats, L-NAME or saline was microinjected into the MPOA before each of 7 daily exposures to a receptive female placed over their cage. In a drug-free test on Day 8, copulation by L-NAME-treated rats was similar to that of unexposed controls and was impaired relative to saline-treated males. Therefore, NO in the MPOA is important for copulation and stimulus sensitization in male rats. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Competition between the conditioned rewarding effects of cocaine and novelty.

Access to novelty might provide an alternative learning history that competes with conditioned drug reward. We tested this suggestion in rats using a place conditioning procedure with cocaine and novelty. In Experiment 1, rats were conditioned with cocaine to prefer one side of an apparatus. In a subsequent phase, cocaine exposure continued; however, on the unpaired side, separate group of rats had access to novel objects, cocaine injections, or saline with no objects. Pairings with novel objects or cocaine shifted a preference away from the cocaine-paired environment during drug-free and drug-challenge tests. Experiment 2 tested novelty's impact when cocaine exposure was discontinued. The identical procedures were used except drug exposure ceased on the cocaine-paired side during the second phase. Both groups expressed a preference for the cocaine compartment. This preference was maintained for rats that did not have novel objects; however, rats that experienced novelty spent similar amounts of time in both compartments during both tests. Overall, the conditioned rewarding effects of novelty competed with those of cocaine as evidenced by a change in choice behaviors motivated by drug reward. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Flavor preferences produced by backward pairing with wheel running.

In 3 experiments rats given 8 sessions of preexposure to wheel running acquired a preference for a flavor that was given immediately after each of 4 subsequent sessions of wheel running. Such flavor preference was less likely when rats were given the same conditioning procedure but without preexposure to wheels (Experiment 1) or when access to flavor was delayed by 30 min following a wheel session (Experiment 2). When rats were given a flavor before each wheel session, the resulting conditioned aversion was greater in rats that had no prior exposure to wheel running (Experiment 3). These results show that whether an aversion or preference for a flavor is produced by wheel running depends on an interaction between prior wheel experience and the sequence of events. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sexual approach conditioning: Unconditioned stimulus factors.

Unconditioned stimulus (US) factors were investigated in a Pavlovian sexual conditioning paradigm with male Japanese quail (Coturnix coturnix japonica). Copulation with a female quail was more effective than exposure to a female without copulation, but the latter also produced conditioned responding (Exp 1). The greater effectiveness of copulatory opportunity as a US was probably not due to nonassociative effects of copulation (Exp 2). Visual cues of the female, as presented on a taxidermic model, were not effective unless the Ss had prior sexual experience that increased their response to the model (Exps 3a and 3b). Successful conditioning with noncopulatory female exposure is significant because it allows for sexual learning to occur in a broader range of circumstances than does conditioning with copulation and because it permits conducting multiple trials per day because males do not become satiated as rapidly. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of dopamine D1 and D2 receptor antagonists on cocaine-induced place preference conditioning in preweanling rats

The effects of dopamine D1 and D2 receptor antagonists on the reward processes of 10- and 17-day-old rats were assessed using the conditioned place preference paradigm. Conditioning and testing were conducted in a three-compartment chamber, with each end compartment having its own distinct tactile and odor cues (almond and lemon). During six experiments, 10- and 17-day-old rats (age at initial conditioning) were injected intraperitoneally with either saline, the dopamine D1 receptor antagonist R(+/-)-SCH 23390 hydrochloride (0.01-1.0 mg/kg), or the dopamine D2 receptor antagonists (+/-)-sulpiride (1-100 mg/kg) or S(-)-eticlopride hydrochloride (0.1-0.5 mg/kg) 30 min prior to being injected with cocaine hydrochloride (20 mg/kg) or saline. After the latter injections, rats were immediately confined in the lemon-scented (nonpreferred) compartment for 30 min. On the alternate conditioning day, rats were injected with saline and confined in the almond-scented compartment. On the third day (i.e., the test day), rats were given saline and allowed free access to the entire chamber for 15 min. The results showed that the dopamine D1 receptor antagonist SCH 23390 blocked the cocaine-induced place preference conditioning of both 10- and 17-day-old rats. Surprisingly, the dopamine D2 receptor antagonists sulpiride and eticlopride blocked the place preference conditioning of 10-day-old rats, while leaving the 17-day-old rats unaffected. These results indicate that dopamine D1 receptors are critically involved in the reward processes of preweanling rats, but that the importance of dopamine D2 receptors changes across ontogeny.     

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)     

Simultaneous second-order conditioning produces S-S learning in conditioned suppression.

Explored simultaneous 2nd-order conditioning of one stimulus (S2) by another (S1) in a conditioned suppression preparation. In Exps I (40 female Holtzman rats) and II (32 male Holtzman rats) 2nd-order conditioning of S2 was attenuated by subsequent extinction of S1. Sequential presentation of the same stimuli produced similar levels of conditioning of S2 that were not affected by extinction of S1, results that replicate previous findings (R. A. Rescorla, 1980). Exps III (32 females) and IV (32 males) found that sensitivity of a simultaneous S2 to changes in S1 depended on S1 receiving few separate reinforced or nonreinforced presentations prior to 2nd-order conditioning. Circumstances are suggested under which the typical stimulus–response learning observed in 2nd-order conditioned suppression can be converted into stimulus–stimulus learning. (13 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)