The objective of the present study was to evaluate the sexual behavior of male rats kept under constant laboratory conditions for one entire year. A total of 213 sexually-inexperienced, male Wistar rats were maintained in controlled environmental conditions from birth. Depending the month in which they reached the age 3-month-old, the male rats were divided into 12 groups, one for each month of the year, and their sexual behavior was evaluated. Records of their sexual behavior were made from 09:00 to 11:00 hrs am. The following parameters were recorded: mount (latency and number), intromission (latency and number), ejaculation latency, and intromission rate. During the months of March, June, July and September, the rats showed lower mount and intromission latencies than in January, February, April, May and October-to-December. Similarly, in March, June, July and August they had higher copulatory efficiency than in January, February, April and December. Results suggest that male rats exposed to controlled environmental conditions could have endogenous mechanisms that regulate sexual behavior but are independent of seasonal environmental signals. The annual variability in the sexual behavior of male rats maintained under constant laboratory conditions should be considered when planning research and experiments.

中文翻译：

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在恒定的实验室条件下保持雄性大鼠交配行为的年度变化。

本研究的目的是评估在恒定实验室条件下饲养一年的雄性大鼠的性行为。从出生开始，共有213只性经验不足的雄性Wistar大鼠维持在受控的环境条件下。根据它们达到3个月大的月份，将雄性大鼠分为12组，一年中的每个月一组，并评估其性行为。他们的性行为记录是从上午09:00到上午11:00。记录以下参数：坐骑（潜伏期和人数），入院（潜伏期和人数），射精潜伏期和入睡率。在3月，6月，7月和9月的几个月中，大鼠的坐骑和内倾潜伏期比1月，2月，4月，5月和10月至12月的低。同样，在三月 6月，7月和8月的交配效率高于1月，2月，4月和12月。结果表明，暴露于受控环境条件下的雄性大鼠可能具有调节性行为的内生机制，但与季节性环境信号无关。在计划研究和实验时，应考虑在恒定实验室条件下维持的雄性大鼠性行为的年度变化。