An optimized approach for the assessment of sexual behavior in male rats

The improvement and optimization of methods used to detect reproductive disorders in experimental animals are among the main challenges facing researchers in this field. The conventional method for testing male sexual behavior uses ovariectomized females rendered sexually receptive by injection of estradiol benzoate and progesterone prior to testing, The receptive females are then mated with exposed male rats during the dark phase of the cycle under dim red light followed by direct visual and momentary observation of the mating activity. The ovariectomized females may respond differently to hormonal injection (individual differences), leading to variations in the intensity of lordosis, Additionally, the data obtained by the direct visual and momentary evaluation of copulatory activity are very subjective and may produce inaccurate results, In the optimized method, the sexual cycles of female rats are determined, and only those in estrus are selected and mated with sexually experienced male rats. The mating activity is videotaped, enabling the correct observation and evaluation of the different components of mating behavior. This method fosters animal welfare by avoiding surgical intervention and enables the videotape to be kept as permanent documentation. (C) 1998 Elsevier Science Inc.