Latent inhibition threshold in Roman high-avoidance rats: A psychogenetic model of abnormalities in attentional filter?

Introduction. Basic research devoted to the study of the psychobiological anomalies of schizophrenia, as well as of its treatments, has used animal models in which some psychotic-like symptoms are induced by administration of psycho-stimulant drugs. There is, however, a growing necessity of having animal models presenting better construct validity, i.e., animal lines spontaneously showing phenotypes associated to the psychotic spectrum (for instance, enhanced sensitivity to psychostimulants, or cognitive and attentional anomalies characteristic of schizophrenic disorders). Several lines of evidence suggest that the RHA (Roman high-avoidance) rat strain presents a neurobehavioral profile which is consistent with such goals. Methods. RHA rats were compared to Sprague-Dawley (SD) rats (as a standard control strain) for the expression of latent inhibition (in a 100-trial session of two-way active avoidance) under threshold conditions (i.e., only 15 preexposures to the conditioned stimulus were administered). Results. Under such experimental conditions SD rats showed significant latent inhibition of the two-way active avoidance response (both during the first 50 trials and in the whole 100-trial session), while that attentional phenomenon did not appear in the RHA strain. Conclusions. The experimental results obtained here indicate that RHA rats display a deficit of latent inhibition at threshold conditions, an information processing (or attentional) anomaly which typically appears in schizophrenic patients. It is proposed that RHA rats might be an useful animal model for the study of vulnerability to some schezophrenic symptoms. This conclusion is supported by data that indicate that latent inhibition deficits are a characteristic attentional abnormality of these diseases.