Successive negative contrast in one-way avoidance learning in female Roman rats.

The inbred RLA (Roman Low-Avoidance) and RHA (Roman High-avoidance) rat strains have been psychogenetically selected for rapid (RHA) vs. extremely poor acquisition (RLA) of two-way active avoidance. As a consequence of this selective breeding, RLA animals exhibit a higher level of emotionality that can be observed in many anxiety models. The present study was conducted in order to analyze the performance of female RLA, RHA and Wistar rats in a behavioral test of anxiety that involves the reduction of the magnitude of an expected reward: the negative contrast effect that is obtained in one-way avoidance learning by reducing the time spent in the safe compartment. To this aim, three groups of animals (30-1/RLA, 30-1/RHA and 30-1/W) were trained to avoid an electric foot-shock administered in a "danger" compartment, by running from this compartment to a "safe" compartment. We observed an impairment of the avoidance response when time spent in the safe compartment was reduced from 30 to 1 s, when 30-1/RLA and 30-1/W groups were compared with control groups that were trained with a constant safe time (1-1/RLA and 1-1/W, respectively). We also obtained significant differences between 30-1/RLA and 30-1/RHA groups in the postshift phase. These results indicate that RLA rats respond more negatively to the frustration triggered by the reduction in time spent in the safe compartment, suggesting that animal models based on negative contrast effects can be useful tools for studying the genetic basis of anxiety.