POTENTIATION OF THE IMMOBILITY RESPONSE ELICITED BY BANDAGING AND CLAMPING IN MESENCEPHALIC RATS

In earlier work, we showed that adult rats exhibit immobility response (IR) if a clamp is fastened to the skin of the nape of the neck, but not at other areas of the body, and not by bandaging. The present stud y characterizes IR in adult rats with complete mesencephalic transecti ons. In the mesencephalic rats, the duration of the IR not only increa sed, but the stimuli capable of eliciting it were more diverse. All he ad and body areas clamped or bandaged were capable of inducing a profo und IR. In contrast, the IR in intact rats was of shorter duration, an d was only induced by clamping the neck, or by bandaging the upper or the lower torso. Furthermore, unlike the mesencephalic rats the abilit y of the bandaging to induce IR is reduced after the first trial and f inally disappears. Only clamping the neck was able to persistently ind uce IR in intact rats. These data support the hypothesis that the IR c ontrol system is in the midbrain, hindbrain or spinal cord, and that s ystems above the mesencephalon modulate the IR. Such modulation appear s to involve the ability to discriminate amongst tactile stimuli, and to integrate previous experience.