Climbing fiber responses evoked in lobule VII of the posterior cerebellum from a vagal nerve in rabbits.

The vagal afferent projection to the cerebellar posterior lobe was examined in decerebrate rabbits with electrophysiological techniques. Electrical stimulation of a vagal nerve at the cervical region evoked field potential responses on both sides of the posterior vermal cortex from lobule VI to VIII. The most prominent potentials appeared in the ipsilateral medial vermis of lobule VIIa. These potentials had a latency of 15.6 ms, and were negative in the molecular layer and positive in the granular layer. At a stimulation rate of 20 Hz, their amplitude was reduced by 70% of the control value at 1 Hz. Superimposed on these field potentials, unitary complex spikes were recorded at the depths of Purkinje cell layers. These results indicate that the medial vermal cortex of lobule VII receives vagal afferent signals via climbing fibers, which presumably convey cardiovascular information.