A comparative study of the behavioral patterns of RLA/Verh and RHA/Verh rats in the exploration box

Roman high- and low-avoidance (RHA/Verh and RLA/Verh) rats differ in their emotionality profiles. As emotional processes are considered to play an important role in exploratory behavior, differences between the Roman sublines in responding to a novel environment can be anticipated. The present study provides a quantitative (based on the frequency of particular responses) and qualitative (based on the frequency of behavioral sequences) comparison of exploratory behavior of RHA/Verh and RLA/Verh rats. Rats of both sexes were tested individually for 30 min in an exploration box containing a few objects. Observation periods were divided, based on earlier studies, into three consecutive blocks of 5, 10, and 15 min, respectively. Analysis of quantitative data showed differences in sniffing (RHA/Verh scoring higher) and in immobility (RLA/Verh scoring higher), both persisting throughout all measurement periods. Males of both sublines were generally more active and exploratory than their respective females. The analysis of sequential data revealed that during the first 5 min RHA/Verh rats showed a less diverse but more exploratory repertoire and that during the first 15 min males of both sublines showed more behavioral sequences than females. This study indicates that the Roman rat sublines should provide a useful model to study the mechanisms of exploratory behavior.