Projection of cardiovascular afferents to the lateral nodulus-uvula of the cerebellum in rabbits.

Vagal and aortic afferent projections to the nodulus and uvula of the cerebellar vermis were examined in anesthetized and paralysed rabbits. Electrical stimulations of vagal and aortic nerves at a frequency of 1/s produced field potentials in the lateral cortical region of the contralateral nodulus-uvula with a latency of 6.5-19 ms. These potentials were negative in the molecular layer and positive in the granular layer. At a higher stimulation rate (30/s), these potentials were reduced by 60-65% of the control value. These results indicate that the lateral cortical region of the nodulus-uvula receives contralateral vagal and aortic afferent signals via climbing fibers. Electrical stimulation of vagal nerves also produced field potentials in the lateral region of the ipsilateral nodulus-uvula with a latency of 6-10.5 ms. Their laminal profile was characteristic of mossy fiber responses. At a higher stimulation rate (30/s), the reduction of these potentials was only 35%. Thus the lateral nodulus-uvula also receives the ipsilateral vagal afferent signals via mossy fibers. Following injection of horseradish peroxidase into the small areas of the lateral nodulus, labeled cells were found in bilateral intercalatus nucleus, prepositus hypogrossal nucleus, Roller nucleus, medial fascicullus longitudinalis, and medial and lateral vestibular nuclei. These nuclei may contain precerebellar neurons in the pathway from the vagal nerve to the lateral nodulus-uvula via mossy fibers.