Climbing fiber representation of the renal afferent nerve in the vermal cortex of the cat cerebellum

Abstract

In order to understand how the cerebellum may participate in various autonomic functions, it is necessary to first determine the occurrence and distribution of the various visceral inputs in the cerebellar cortex and their relation to other cerebellar afferents. This study examines the organization of climbing fiber responses (complex spikes) of Purkinje cells elicited by electrical stimulation of the renal afferent nerve and their relationship to climbing fiber responses representing the body surface. Visceral and somatic afferent responses were mapped in the lateral vermal cortex of lobules V to VII in chloralose-anesthetized cats. Extracellular single-unit recordings were made from 628 Purkinje cells, of which 14% had climbing fiber responses induced by renal afferent nerve stimulation. Except for one Purkinje cell, the renal climbing fiber input converged with somatic induced climbing fiber input. Tactile stimulation also elicited 54% of cells, which were unresponsive to the renal afferent nerve stimulation. The occurrence and distribution of the climbing fiber responses elicited by renal afferent nerve stimulation varied between lobules V, VI, and VII for the proportion of responsive units, the onset latencies, and topological organization. More renal responsive units were encountered in lobules V (18%) and VII (17%) than in lobule VI (6%), the average latency of renal climbing fiber responses was significantly longer in lobule VII than in lobules V and VI, and the latencies were also different among various parasagittal planes in lobules V and VII. The proportional representation of various body areas for cells with renal and somatic convergent input was different than for cells with only somatic representation. Proportionally, the forelimb had the greatest representation in lobule V, split receptive fields were frequently represented in lobule VI, and the face was well represented in lobule VII. The results of this study, in conjunction with studies showing climbing fiber representation of the vagal and splanchnic nerves, further substantiate role of the cerebellum in autonomic functions.