The projection of splanchnic afferents on the cerebellum of the cat.

1. The projections of the ipsilateral and contralateral splanchnic nerves on the cerebellum were studied in cats under sodium thiopentone anaesthesia.2. The splanchnic nerves were electrically stimulated. Evoked potentials and single unit discharges were recorded by means of 2.5 M-NaCl-filled glass micropipettes. A responsive region was found in the intermediate cortex of lobules Vb to f of the anterior lobe.3. The Agammadelta fibres of the splanchnic nerve had a bilateral cerebellar representation. The Abeta fibres were represented only on the ipsilateral side.4. At the level of the upper cervical spinal cord, fibres from the ipsilateral splanchnic nerve were conveyed in both the dorsal and lateral funiculi; fibres from the contralateral nerve were restricted to the ipsilateral lateral funiculus.5. On the basis of the characteristic potential fields generated in the cerebellar cortex, it is concluded that the majority of the splanchnic afferents studied terminate in the cerebellum as climbing fibres. A few responses of short latency may have been due to a mossy fibre input.6. In interaction experiments, a conditioning stimulus to one splanchnic nerve depressed the response to stimulation of the other nerve for up to 80-100 msec, the effect being most pronounced at 40-50 msec. During this period, spontaneous activity of the cerebellar unit was also suppressed.7. The organization of the splanchnic pathways to the cerebellum and their terminal connexions are discussed.