Titration schedule with rats in a restraining device.

In a restraining device, providing a constant localization and easy placement of stimulating electrodes, rats were conditioned to push a front panel in order to reduce the intensity of a shock which otherwise increased regularly every 10 sec. Rapid conditioning was obtained from all subjects. They showed a very stable behavior, with negligible inter- or intra-individual variability throughout very long experimental sessions. The operant nature of the response was demonstrated further in extinction, where no shock was delivered, and in situations where the animal could not change the predetermined intensity of the shock. The interpretation of the obtained threshold was discussed with reference to previous studies on titration schedule. It was suggested that, with the parameters used, the shock intensity at which it was maintained by the rats' behavior, had the value of a warning signal, and that, in this particular case, the titration schedule generated mainly discriminative avoidance behavior rather than escape behavior.