Strain differences in latent inhibition

Latent inhibition (LI) - that is, retarded conditioning to a stimulus following its nonreinforced preexposure - was tested in inbred Buffalo Dark- Agouti (DA) rats. Unlike albino outbred Wistar rats, which showed LI to both tone and flashing light in a conditioned emotional response (CER) procedure, DA rats showed LI to light but not to tone. The same pattern was obtained in DA rats in a two-way active-avoidance procedure. In addition, DA rats failed to show LI to white noise. LI to tone in CER was not restored by increasing the number of preexposures or by the administration of haloperidol. This is a first demonstration of strain differences in LI acquisition. Since LI disruption characterizes specific neuropsychiatric disorders, the elucidation of the mechanisms underlying the failure to develop LI, when this failure is not caused by external manipulations (e.g., by a drug or a lesion), may be important for understanding the neural substrates of this deficit.