STRAIN DIFFERENCES IN LATENT INHIBITION

Latent inhibition (LI)-that is, retarded conditioning to a stimulus fo llowing its nonreinforced preexposure-was tested in inbred Buffalo Dar k-Agouti (CD) 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 p attern 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 t he administration of haloperidol. This is a first demonstration of str ain differences in LI acquisition. Since LI disruption characterizes s pecific 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 import ant for understanding the neural substrates of this deficit.