Somatotopically inappropriate projections of single hair follicle afferent fibres to the cat spinal cord.

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Abstract
In the [lumbar] L7 segment of cats anesthetized with .alpha.-chloralose, single hair follicle afferent (hfa) fibers were injected intra-axonally with horseradish peroxidase (HRP). In the same animal light tactile stimuli were used to plot the receptive fields of laminae III and IV dorsal horn neurones (dhn) at various rostrocaudal levels below the stained segment of axon. Of the 10 injected axons 8 gave rise to collaterals in somatotopically inappropriate regions of the dorsal horn, i.e., those regions in which the receptive fields of dhn did not emcompass the receptive field of the stained hfa. Overall the stained hfa gave rise to 53 collaterals, 22 (42%) of which projected to somatotopically inappropriate regions of the dorsal horn. Collateral arborizations in the somatotopically inappropriate region were always located in the same mediolateral region of the dorsal horn as those arborizations in the appropriate region. Collateral arborizations > 600 .mu.m from the somatotopically appropriate region had few branches and gave rise to very few boutons compared with those within the appropriate region.