Effects of 5-HT3 agonists on reproductive behaviors in rats.

Activity at 5-HT1 and 5-HT2 receptor sites influences sexual behavior in male and female rats. 5-HT3 antagonists reportedly have no effect on copulatory activity in rats of either sex although they influence a variety of other behaviors. The effects of 5-HT3 agonists on sexual behavior are unknown. The following experiments were undertaken to assess the influence of the 5-HT3 agonists 1-phenylbiguanide (PBG) and 2-methyl-serotonin (2-Me-5-HT) on sexual behavior, when administered intracerebroventricularly. Consistent with earlier reports indicating that 5-HT1 and 5-HT2 receptor activity influences reproductive activity in a sex-dependent manner, PBG was found to facilitate male, but not female, rat sexual behavior. 2-Me-5-HT, however, failed to modify either female or male rat sexual activity. Evidence that PBG, but not 2-Me-5-HT, induces carrier-mediated dopamine release suggests that the effect of PBG in male rats is due to dopaminergic mediation. Overall, the present data indicate that 5-HT3 receptor activation has only slight effects on rat sexual behavior.

Cohabitation with a sterile male facilitates the development of retrieval behavior in nulliparous female rats exposed to pups.

Female rats were housed with a sterile male or another female. After 3 weeks, half of the females that had been housed with a female were rehoused with an intact male. At the end of 6 weeks female or sterile male cagemates were removed. Intact male cagemates and pups were removed 3 to 12 h following parturition. All females were tested for retrieval of three unfamiliar pups placed in their cage on the day following removal of their cagemate. Three unfamiliar pups were placed with each female and the female's behavior observed for 10 min. Observations were made in this way for 13 days or until the female retrieved all three pups within the 10-min interval. Pups were left with the female on days they were not retrieved. Females housed with a sterile male reached criterion for pup retrieval in 2.9 days, significantly fewer days than were required for females housed with another female (6.6 days) but significantly more than were required for a postpartum female (0.8 days). By demonstrating that cohabitation with a male fosters the development of retrieval, these results support evidence from the study of aggressive behavior that pseudopregnancy facilitates the development of behaviors associated with pregnancy and lactation.

Effects of the oxytocin fragment prolyl-leucyl-glycinamide on sexual behavior in the rat.

Prolyl-leucyl-glycinamide (PLG), a natural brain peptide, is identical in structure to the C-terminal of oxytocin. Moreover, PLG and oxytocin can act as opiate antagonists. Evidence that opiates and oxytocin have significant influences on reproductive behavior suggests that PLG may also be effective. Morphine and/or PLG were administered intraperitoneally to male and female rats and sexual behavior was observed. PLG (0.1-10 mg/kg) was found to facilitate female sexual behavior in Experiment 1. In Experiment 2, the ability of PLG to facilitate female receptivity was found to be progesterone dependent. In Experiment 3, tyrosine-prolyl-leucyl-glycinamide, a putative precursor to PLG, failed to facilitate lordosis. In Experiment 4, PLG failed to facilitate male sexual behavior. In Experiments 5 and 6, PLG did not affect morphine-induced inhibition of either male or female sexual behavior. These data suggest that PLG differentially affects female receptivity and male sexual behavior. The current results support the hypothesis that PLG is an active metabolite of oxytocin in the female, but do not provide evidence that PLG functions as an opiate antagonist of sexual behavior.

Lack of effects of 5-HT3 antagonists on normal and morphine-attenuated sexual behaviours in female and male rats.

Although 5-HT1 and 5-HT2 receptor activity is known to influence copulation, the effects of 5-HT3 receptor-selective drugs on sexual activity have yet to be systematically studied. The following experiments investigated the effects of the 5-HT3-selective antagonists MDL 72222, ondansetron and ICS 205-930 on female sexual behaviour; male rats were studied using ondansetron and granisetron. These compounds influenced neither male nor female copulatory behaviours, suggesting that 5-HT3 receptors contribute little to the modulation of sexual activity. 5-HT3 receptor antagonists block certain opioid-induced behaviours and opioids selectively inhibit sexual behaviours; therefore, the ability of ondansetron and ICS 205-930 to modify morphine-attenuated copulatory activity was also tested. While morphine inhibited copulation, 5-HT3 antagonists failed to reverse the effects.

Social determinants of experienced anger.

We investigated two social determinants (i.e., availability of social support and status differentials of the provocateur) for the degree of perceived anger in two populations. Because no suitable tool was available, the conceptual and psychometric development and validation of a new vignette-based measure for anger level (STandardized Experience of Anger Measure, STEAM) is described first. Two versions of STEAM were developed: one for students and one for community-living adults. Through a series of four studies, two sets of a 12-item vignette-based questionnaire were developed and validated. The resulting test had excellent test-retest stability and high internal consistency. Using the new STEAM measure, a variety of analyses were conducted to test the hypothesized influence of social determinants of anger. In the student sample, presence of social support was associated with lessened anger, and in both samples decreasing status of the provocateur also led to lessened anger arousal. In addition, findings in both samples revealed that social support reduced anger when the provocateur was of higher status relative to situations of equal and lesser status. In the community sample, the availability of support was associated with greater intensity of the anger experience in the lesser status condition than in the equal or greater status condition. No gender main effects or interactions were noted.