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Collateral sprouting of the central terminals of cutaneous primary afferent neurons in the rat spinal cord: Pattern, morphology, and influence of targets
Author(s) -
Fitzgerald Maria,
Woolf Clifford J.,
Shortland Peter
Publication year - 1990
Publication title -
journal of comparative neurology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.855
H-Index - 209
eISSN - 1096-9861
pISSN - 0021-9967
DOI - 10.1002/cne.903000308
Subject(s) - spinal cord , anatomy , sprouting , biology , sciatic nerve , axon , peripheral , receptive field , horseradish peroxidase , neuroscience , medicine , botany , biochemistry , enzyme
Abstract The capacity of the central terminals of primary afferents to sprout into denervated areas of neonatal spinal cord and the morphology of any novel terminals has been investigated. In rats which had undergone sciatic nerve section on the day of birth, 12 of 18 physiologically characterized intact saphenous hair follicle afferents (HFAs) were labelled intra‐axonally with horseradish peroxidase (HRP) were shown to sprout up to 2,000 m̈m into the deafferented sciatic terminal field. The morphology of these sprouts depended on which area of the sciatic nerve territory was invaded by the afferent sprouts. Six HFAs sprouted into areas normally innervated by glabrous skin afferents and the morphology of the collateral sprouts in this region resembled that of rapidly adapting (RA) afferents. The other six saphenous HFAs had sprouted into sciatic “hairy” skin areas and the morphology of these sprouts, although abnormal, was flame shaped. In rats whose sural, saphenous, and superficial peroneal nerves were cut at birth, 4 of 7 single HRP labelled RA afferents had central terminals that had sprouted into regions of cord normally devoted to “hairy” input. These showed clear signs of HFA morphology despite their peripheral receptive fields remaining in the glabrous skin. The results show collateral sprouting of single cutaneous sensory afferent axons into adjacent inappropriate central target regions following neonatal deafferentation. Such plasticity may provide some compensation following neonatal injury. The morphology of the sprouted terminals is appropriate to the new target area rather than to its functional class and is also independent of the peripheral receptive field location providing an example of central rather than peripheral control over afferent growth patterns.