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Preoptic glutamate facilitates male sexual behavior
Juan M Dominguez1, Mario Gil, Elaine M Hull
1Department of Psychology, Neuroscience Program, Florida State University, Tallahassee, Florida 32306-1270, USA.
Abstract:
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 [approximately 140% of baseline (BL)] rise in extracellular glutamate when the female was presented, a significant increase (approximately 170% of BL) during periods of mounting and intromitting, and a very large increase in samples collected during ejaculation (approximately 300% 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 (approximately 280% 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.
Insights
Glutamate in the medial preoptic area (MPOA) significantly increases during male rat mating, peaking at ejaculation. A subsequent fall in MPOA glutamate levels regulates the post-ejaculatory interval.
Area of Science:
- Neuroscience
- Behavioral Neuroscience
- Neuroendocrinology
Background:
- The medial preoptic area (MPOA) is a key brain region for regulating male sexual behavior.
- Understanding the neurochemical mechanisms underlying sexual behavior is crucial for addressing related disorders.
Purpose of the Study:
- To investigate the role of glutamate in the MPOA during male rat copulation.
- To determine how extracellular glutamate levels change before, during, and after mating.
- To examine the effect of modulating MPOA glutamate on sexual behavior parameters.
Main Methods:
- Microdialysis was used to measure extracellular glutamate levels in the MPOA of male rats before, during, and after copulation.
- Glutamate uptake inhibitors were administered via reverse-dialysis into the MPOA during mating.
- Behavioral parameters, including ejaculation latency and post-ejaculatory interval, were recorded.
Main Results:
- Extracellular glutamate in the MPOA increased progressively during mounting, intromission, and ejaculation.
- A sharp decrease in MPOA glutamate was observed immediately post-ejaculation, correlating with the duration of sexual quiescence.
- Inhibition of glutamate uptake in the MPOA enhanced sexual behavior, increasing ejaculations and reducing latencies.
Conclusions:
- MPOA glutamate acts as a significant facilitator of male copulatory behavior.
- The dynamic changes in MPOA glutamate, particularly the post-ejaculatory fall, play a critical role in regulating sexual behavior and refractory periods.
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