The medial preoptic area (MPOA) is a critical regulatory site for the control of male sexual behavior. We first measured glutamate in 2 min microdialysate samples from the MPOA before, during, and after copulation by male rats. There was a slight [ϳ140% of baseline (BL)] rise in extracellular glutamate when the female was presented, a significant increase (ϳ170% of BL) during periods of mounting and intromitting, and a very large increase in samples collected during ejaculation (ϳ300% of BL). A precipitous fall in levels occurred in the first postejaculatory sample; the magnitude of this fall was highly correlated with the length of the postejaculatory interval of quiescence. In experiment 2, we reverse-dialyzed a mixture of glutamate uptake inhibitors into the MPOA before and during mating; control animals received artificial CSF. The mixture increased extracellular glutamate (ϳ280% of BL), increased the number of ejaculations in the 40 min test, decreased ejaculation latency, and decreased the postejaculatory latency to resume copulation. These data, together with other findings that glutamate in the MPOA can elicit genital reflexes in anesthetized rats and that glutamate receptor antagonists in the MPOA impair copulation, strongly suggest that MPOA glutamate is a major facilitator of copulation and that the postejaculatory fall in glutamate regulates the postejaculatory interval.
Oxytocin (OT) is a versatile neuropeptide that is involved in a variety of mammalian behaviors, and its role in reproductive function and behavior has been well established. The majority of pharmacological studies of the effects of OT on male sexual behavior have focused on the paraventricular nucleus (PVN), ventral tegmental area (VTA), hippocampus, and amygdala. Less attention has been given to the medial preoptic area (MPOA), a major integrative site for male sexual behavior. The present study investigated the effects of intra-MPOA administration of OT and (d(CH2)51, Tyr(Me)2, Thr4, Orn8, Tyr-NH29)-vasotocin, an OT antagonist (OTA), on copulation in the male rat. The relationship between OT receptor (OTR) binding levels in the MPOA and sexual efficiency was also explored. Microinjection of OT into the MPOA facilitated copulation in sexually experienced male rats, whereas similar injections of an OTA inhibited certain aspects of copulation but had no significant effect on locomotor activity in an open field. Contrary to expectation, sexually efficient males had lower levels of OTR binding in the rostral MPOA compared to inefficient animals. The present data suggest that OT activity in the MPOA is not necessary for the expression of male sexual behavior but is sufficient to facilitate copulatory behaviors and improve sexual efficiency in sexually experienced male rats. These data also suggest that OTR activity in the MPOA stimulates anogenital investigation, facilitates the initiation of copulation, and plays a role in the sensitization effect of the first ejaculation on subsequent ejaculations.
Oxytocin (OT) promotes social and reproductive behaviors in mammals, and OT deficits may be linked to disordered social behaviors like autism and severe anxiety. Male rat sexual behavior is an excellent model for OT regulation of behavior, as its pattern and neural substrates are well characterized. We previously reported that OT microinjected into the medial preoptic area (MPOA), a major integrative site for male sexual behavior, facilitates copulation in sexually experienced male rats, whereas intra-MPOA injection of an OT antagonist (OTA) inhibits copulation. In the present studies, copulation on the day of sacrifice stimulated OTR mRNA expression in the MPOA, irrespective of previous sexual experience, with the highest levels observed in first-time copulators. In addition, sexually experienced males had higher levels of OTR protein in the MPOA than sexually naïve males and first-time copulators. Finally, intra-MPOA injection of OT facilitated mating in sexually naive males. Others have reported a positive correlation between OT mRNA levels and male sexual behavior. Our studies show that OT in the MPOA facilitates mating in both sexually naive and experienced males, some of the behavioral effects of OT are mediated by the OTR, and sexual experience is associated with increased OTR expression in the MPOA. Taken together, these data suggest a reciprocal interaction between central OT and behavior, in which OT facilitates copulation and copulation stimulates the OT/OTR system in the brain.
Nitric oxide in the medial preoptic area (MPOA) is important for the expression and sensitization of male sexual behavior. In this article, the authors report that repeated sexual experience (mating for 2 hr on each of 3 days) increased levels of nitric oxide synthase (NOS) in the MPOA of male rats, regardless of whether they mated on the day they were given an overdose of sodium phenobarbital. This effect resulted from the previous experience and not acute mating, as NOS was not increased 2 hr after the first mating in previously naive males. Experience-induced increases in NOS in the MPOA may be one mechanism through which sexual experience facilitates sexual behavior in male rats.
Objective. To assess the feasibility of a parent mentor model of intervention for early childhood obesity using positive deviance-based methods to inform the intervention. Methods. In this pilot, randomized clinical trial, parent-child dyads (age: 2–5) with children whose body mass index (BMI) was ≥95th percentile were randomized to parent mentor intervention or community health worker comparison. The child's height and weight were measured at baseline, after the six-month intervention, and six months after the intervention. Feasibility outcomes were recruitment, participation, and retention. The primary clinical outcome was BMI z-score change. Results. Sixty participants were enrolled, and forty-eight completed the six-month intervention. At baseline, the BMI z-score in the parent mentor group was 2.63 (SD = 0.65) and in the community health worker group it was 2.61 (SD = 0.89). For change in BMI z-score over time, there was no difference by randomization group at the end of the intervention: −0.02 (95% CI: −0.26, 0.22). At the end of the intervention, the BMI z-score for the parent mentor group was 2.48 (SD = 0.58) and for the community health worker group it was 2.45 (SD = 0.91), both reduced from baseline, p < 0.001. Conclusion. The model of a parent mentor clinical trial is feasible, and both randomized groups experienced small, sustained effects on adiposity in an obese, Hispanic population.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.