Dorsal pressure potentiates the duration of tonic immobility and catalepsy in rats.

This study tested the generalizations that cutaneous pressure will elicit immobility, that there is a relationship between the intensity of cutaneous pressure and the duration of immobility, and that the localization or body surfaces, particularly the upper dorsal area or the nape of the neck, is more susceptible to immobility. Immobility was measured by the duration in sec of tonic immobility, bar grasp and vertical cling behaviors or catalepsy. It was shown in the first experiment that dorsal pressure immobility can be elicited in the adult rat. The application of a 9-kg pressure elicited a significant potentiation of the duration of tonic immobility and the bar grasp catalepsy and both 5 and 9 kg of pressure potentiated the duration of vertical cling catalepsy. In the second experiment, only pressure applied to the midline of the dorsal surface at the nape of the neck significantly potentiated the duration of these measures. These results were compared with other experimentally and naturally occurring immobilities.