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Updated: May 25, 2026
Assessment of Sexual Behavior of Male Mice
Published on: March 5, 2020
An NMDA antagonist in the MPOA impairs copulation and stimulus sensitization in male rats
Anna V Vigdorchik1, Bradley P Parrish, Gwen A Lagoda
1Department of Psychology, State University of New York at Buffalo, USA.
Abstract:
Systemic injections of an NMDA antagonist have been shown to impair mating in male rats. One site where glutamate and its NMDA receptors may contribute to mating is the medial preoptic area (MPOA), which is vital for male sexual behavior. Glutamate is released in the MPOA during copulation, and especially at the time of ejaculation. We report here that the NMDA antagonist MK-801, microinjected into the MPOA, impaired copulatory behavior in sexually naïve as well as experienced males. In rats tested both as naïve and after sexual experience, drug treatment produced more profound impairment in naïve males. In addition, MK-801, microinjected into the MPOA before each of 7 noncopulatory exposures to receptive female rats, resulted in copulatory impairments on a drug-free test on Day 8, relative to aCSF-treated rats; their behavior was similar to that of males that had not been preexposed to females. Therefore, NMDA receptors in the MPOA contribute to the control of copulation and stimulus sensitization. Glutamate, acting via NMDA receptors, regulates many neural functions, including neuronal plasticity. This is the first demonstration that a similar mechanism in the MPOA sensitizes male rats to the stimuli from a receptive female, and thereby enhances their behavior.
Insights
NMDA receptors in the medial preoptic area (MPOA) are crucial for male rat mating behavior. Blocking these receptors impairs copulation and reduces sensitivity to female cues.
Area of Science:
- Neuroscience
- Behavioral Neuroscience
- Reproductive Biology
Background:
- Glutamate and NMDA receptors play roles in neural functions, including plasticity.
- The medial preoptic area (MPOA) is vital for male sexual behavior.
- Glutamate is released in the MPOA during copulation, particularly at ejaculation.
Purpose of the Study:
- To investigate the role of NMDA receptors in the MPOA in controlling male rat copulatory behavior.
- To determine if NMDA receptor activity in the MPOA influences sensitization to female sexual stimuli.
Main Methods:
- Microinjection of the NMDA antagonist MK-801 into the MPOA of male rats (sexually naïve and experienced).
- Behavioral testing of copulatory performance after drug administration.
- Assessing the effects of MPOA NMDA receptor blockade on sensitization to female cues through repeated non-copulatory exposures.
Main Results:
- Microinjection of MK-801 into the MPOA significantly impaired copulatory behavior in both naïve and experienced male rats.
- The impairment was more pronounced in sexually naïve males.
- Pre-exposure to receptive females followed by MPOA MK-801 treatment resulted in copulatory deficits, similar to males not pre-exposed, indicating impaired stimulus sensitization.
Conclusions:
- NMDA receptors within the MPOA are essential for the regulation of male rat copulation.
- NMDA receptor activation in the MPOA contributes to stimulus sensitization, enhancing male rats' responsiveness to receptive females.
- This study demonstrates a mechanism by which NMDA receptors in the MPOA modulate sexual behavior through neuronal plasticity and sensitization.
