| Research Abstract |
Three pairs of nonspiking giant interneurons (G1, G2, G3 ; NGIs) respond with depolarizing or hyperpolarizing graded potentials to visual stimuli (Okada and Yamaguchi, 1989). In the present experiments, we obtained the following results.
The NGIs respond with depolarizing and hyperpolarizing graded potentials to body tilt in roll to the ipsi- and contralateral sides in the dark. In ipsilaterally statocystectomized animals, all the NGIs respond with hyperpolarizing potentials only to the contralateral side-down tilt, whereas in contralaterally statocystectomized animals, they respond with depolarizing potentials only to the ipsilateral side-down tilt. In bilaterally statocystectomized animals, none of the NGIs respond to body tilt in the dark, but in the presence of a overhead light, they exhibit depolarizing and hyperpolarizing potentials in response to body tilt to the ipsi- and contralateral sides, respectively. The amplitude of visual responses varies in association with the amplitude of the geotactic response produced by body tilt. On the other hand, in bilaterally statocystectomized animals the NGIs respond with depolarizing and hyperpolarizing graded potentials to upward and respond to substrate tilt about the longitudinal axis of the body in the dark. Relationships between the polarity of potential and the direction of movement in the contralateral walking legs were just opposite to those in the ipsilateral walking legs. In intact animals the NGIs hardly respond to leg movements in the dark.
These results indicate that the NGIs integrate the sensory inputs from eyes, statocysts, and leg proprioceptors and that the interaction between sensory inputs from the left and right sensory organs with either the same modality or with different modalities enhance the directional sensitivity of NGIs as premotoneurons in the compensatory oculomotor system.
|
