Journal of Neurophysiology, Vol 70, Issue 6 2399-2410, Copyright © 1993 by APS
Morphology of A beta hair follicle afferent collaterals in dorsal horn of cats with neonatal chronic denervation of digits
P. Wilson and P. J. Snow
Department of Anatomical Sciences, University of Queensland, Australia.
1. The effect of neonatal denervation of two adjacent hindpaw digits
(digits 3 and 4) in the cat on the morphology of spinal collaterals of
identified A beta hair follicle afferents (HFAs) with receptive fields
(RFs) on the neighbouring digits has been investigated using intra-axonal
injection of horseradish peroxidase. 2. The morphology of collaterals of
HFAs innervating intact digits (digit 2 or digit 5) was examined within the
neonatally and chronically deprived region of dorsal horn by selectively
injecting the afferents directly over this region. 3. Of a total of nine
injected axons, seven had RFs on the distal part of digit 2, whereas two
had RFs on the distal part of digit 5. With the exception of one of the
digit 5 afferents, all injected afferents gave rise to stained collaterals
throughout the chronically deprived digit representation. 4. Many
collaterals within the chronically deprived region of dorsal horn gave rise
to arborizations having relatively large numbers of boutons when compared
with previously described somatotopically inappropriate (SIA) collaterals
in the normal adult cat. 5. It is suggested that neonatal denervation of
digits in the cat may lead to collateral sprouting and bouton formation by
SIA collaterals of A beta HFAs innervating adjacent intact digits. This
morphological plasticity could explain the previously reported functional
reorganization of the RFs of spinocervical tract neurons that occurs in
these neonatally deafferented animals.
