VARIATION OF DORSAL HORN CELL DENDRITIC SPREAD WITH MAP SCALE

Cells in laminae III, IV, and V of cat dorsal horn were injected with horseradish peroxidase or neurobiotin. Dorsal views of the dendritic d omains were constructed in order to measure their lengths, widths, are as, and length/width ratios in the horizontal plane (the plane of the somatotopic map). Dendritic domain width and area in the horizontal pl ane were negatively correlated with fractional distance between the me dial and lateral edges of the dorsal horn. These results are consisten t with the hypothesis that dendritic domain width varies with map scal e, which is maximal in the medial dorsal horn. This is similar to the variation in widths of primary afferent bouton distributions. The para llel variation of dorsal horn cell dendritic domain width and primary afferent bouton distribution width with map scale suggests that there is a causal relation between morphology and map scale in the dorsal ho rn representation of the hindlimb. This variation of adult morphology with map scale must reflect mechanisms responsible for the assembly of receptive fields. (C) 1996 Wiley-Liss, Inc.