Fear-dependent variations in continuous avoidance behavior of pigs. I. Lack of effect of diazepam on performance of discriminative fear conditioning.

Pigs trained to avoid shocks by crossing a barrier in a shuttle-box according to a continuous avoidance procedure were submitted to a Pavlovian discriminative fear-conditioning procedure in which a tone was always followed by unavoidable shock (CS+) and another tone never followed by shock (CS-). The presentation of the CS+ on a test session in the shuttle-box induced an increase of the response rate while the CS- decreased the performance. Diazepam (1 mg/kg) administered before the test session did not modify the changes in avoidance response to each CS.