Effects of Preweaning Noxious Stimulation on Later Behavior of Rats: Role of Experimenter Contact and Spacing of Stimulation

Abstract

The role of experimenter contact in preweaning stimulation experiments was examined by comparing the behavior of rats receiving noxious stimulation in their home environment without intervention by E to that of rats stimulated in a novel environment. In Exp. 1, 160 Wistar rats were undisturbed or subjected to a loud noise massed at either 2 or 21 days of age or spaced throughout the preweaning period. Adult testing revealed no differences between in-cage and out-of-cage groups but supported the earlier findings that spaced noxious stimulation increased subsequent emotionality less than massed stimulation. Blood sugar levels were higher for massed groups than for spaced or undisturbed groups. All groups receiving preweaning stimulation showed less emotional reactivity after an adult stressor than undisturbed Ss. In Exp. 2, 220 rats were undisturbed or subjected to cold stress in a design similar to that of Exp. 1. Results were similar in that massed groups were more emotional than spaced groups and that few clear in-cage vs out-of-cage differences were found.