Somatosensory pressure affects immobility and grasping reactions in bilateral labyrinthectomized rats.

The effects of dorsal clip pressure and proprioceptive plate pressure to soles of the feet on tonic immobility; dorsal clip pressure on contact righting, horizontal bar, and vertical cling; forepaw and slope board grasp reactions were investigated in bilateral labyrinthectomized (BL) rats. Both dorsal and proprioceptive pressures potentiated the duration of tonic immobility in BL animals whereas only the dorsal pressure affected the controls. Dorsal pressure potentiated the duration of the horizontal bar, vertical cling, and slope board grasps in both the control and BL group. However, the behavioral patterns were different. The BL animals had weak grasp reactions and with the dorsal clip, emitted "head-back fall" during the vertical cling and slope board grasp conditions. The results were discussed in terms of the tactile and vestibular interactions and control on the postural mechanisms.