Research paperProximity as a predictor of social behavior in rats

•A simple method for estimating social behavior of a single rat is proposed.•The method measures the time a rat attempts to interact with a co-specific.•The method does not require special conditions or special training from experimenter.•The measure is stable under several conditions and sensitive to at least one drug.

BackgroundIn studies that measure social behavior of a freely interacting pair rats social behavior of one rat is strongly influenced by the behavior of the other. This prevents evaluating social behavior of one single rat.New methodWe assessed the motivation to interact socially in a modified open-field, by measuring the time a rat attempted to interact with a co-specific separated by a grid in a birdcage outside of the apparatus. We propose time in front of the birdcage is an indicator of social behavior.ResultsWe showed that the focal rat allocates more time in front of the birdcage, interacting with another rat through the grid. Also, that the presence of the other rat that attracts the focal rat. Habituation to the apparatus, repeated testing and illumination condition did not alter the proximity measures of rats. Finally, treatment with chlordiazepoxide (3.0 mg/kg) either increased the time spent in front of the cage by males and females or (5.6 mg/kg) increased the proximity measure of females.Comparing with existing methodOur method prevents partners from influencing the target rat's social behavior; existing methods do not. Also, it is more sensitive to the effect of chlordiazepoxide than the broadly used method proposed by File and Hyde (1978).ConclusionsProximity is an advantageous measure: it allows the assessment of only one focal animal without the interference of a partner; it is simple to take; it requires little interpretation skills or training from the experimenter, no special equipment or conditions.