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

The improvement and optimization of methods used to detect reproductive dis orders in experimental animals are among the main challenges facing researc hers in this field. The conventional method for testing male sexual behavio r uses ovariectomized females rendered sexually receptive by injection of e stradiol benzoate and progesterone prior to testing, The receptive females are then mated with exposed male rats during the dark phase of the cycle un der dim red light followed by direct visual and momentary observation of th e mating activity. The ovariectomized females may respond differently to ho rmonal injection (individual differences), leading to variations in the int ensity of lordosis, Additionally, the data obtained by the direct visual an d momentary evaluation of copulatory activity are very subjective and may p roduce inaccurate results, In the optimized method, the sexual cycles of fe male rats are determined, and only those in estrus are selected and mated w ith sexually experienced male rats. The mating activity is videotaped, enab ling the correct observation and evaluation of the different components of mating behavior. This method fosters animal welfare by avoiding surgical in tervention and enables the videotape to be kept as permanent documentation. (C) 1998 Elsevier Science Inc.