Assessment of Sexual Behavior of Male Mice

Sexual behavior is a dynamic and a complex process that's influenced by biologic, social, and the environment factors. The study of mouse sexual behavior can provide more information about this interactions. This procedure facilitates the recording of the number and the duration of male mice sexual behaviors to allow the identification and the characterization of mouse sexual behavior interactions and the patterns.

48 hours before the sexual behavior test, inject 20 micrograms of Estradiol benzoate in 100 microliters of sterilized olive oil intraperitoneally into a six to eight week old female mouse to induce estrus. On the same day, place the male mice to be tested in the center of a 40 by 40 by 40 centimeter square open field box with three black plexiglass walls and one transparent front wall. Allow the animals to explore the environment freely for 30 minutes per day for the next two days.

On the day of the test, four hours before the experiment inject 500 micrograms of progesterone in 100 microliters of sterile olive oil intraperitoneally into the female mice and set the room lighting to 650 lux. Then set up a digital camera linked to a computer to videotape the movement and behavior of the mice. To conduct the behavioral assay, during the first hours of the dark cycle turn on the camera and place the male mouse to be tested in the center of the open field in the test box for five minutes.

When the mouse has acclimated to the test environment, place a female mouse in hormone induced estrus into the test box and record the social and mating behaviors and interactions between the male and female mice for 30 minutes. At the end of the test period, confirm that the video has been saved and turn off the camera. Return the mice to their individual home cages and clean any urine, feces, and padding within the apparatus.

Then remove the smell of the tested animals with 75%ethanol and begin the test for the next male mouse as just demonstrated. To analyze the behavioral data, when all of the mice have been tested play back the video recording and record the number of mounts and the number of intromissions that occurred during the 30 minute experimental period. Record the time from the introduction of the female to the first mounting as the mounting latency, the time from the introduction of the female to the first intromission as the intromission latency, and the time from the first intromission to the first ejaculation as the ejaculation latency.

Then record the number and the time of all the copulatory series in 30 minutes. The success rate of copulation tends to be lower in isolation reared groups than in group housed groups, likely due, at least in part, to the longer mounting latency observed in isolation reared groups compared to the group housed groups. The intromission latency is also longer in isolation reared groups indicating that these animals require a longer time to perform the insertion of the penis into the female's vagina.

No statistically significant difference between the two groups is observed in terms of ejaculation latency or post-ejaculatory mount latency. The duration of the copulatory series is shorter in the isolation housed group than in the group housed group. No statistically significant differences between the two groups are observed in terms of the number of mounts, number of intromissions, or number of copulatory series.

Sexual behavior is a refraction of neural and the neurocrine function. Understanding mouse sexual behavior patterns can help further our understanding of human sexual behaviors and their interactions.