Journal of Neuroscience, Vol 9, 548-557, Copyright © 1989 by Society for Neuroscience
Physiological and anatomical consequences of infraorbital nerve transection in the trigeminal ganglion and trigeminal spinal tract of the adult rat
WE Renehan, BG Klein, NL Chiaia, MF Jacquin and RW Rhoades
Department of Anatomical Sciences and Neurobiology, University of Louisville School of Medicine, Kentucky 40292.
Single-unit recording and retrograde tracing techniques were used to assess
the receptive field properties, topography, and projections of rat
trigeminal primary afferent neurons subsequent to transection of the
infraorbital (IO) nerve in adulthood. Four hundred and fifty-eight units
were recorded in the trigeminal ganglion ipsilateral to nerve section. Of
these, 66.6% had IO receptive fields. Thirty percent responded to innocuous
stimulation of vibrissae, 39.1% to guard hair deflection, 8.2% to gentle
indentation or stretch of the skin, and 22.3% to noxious stimuli (compared
to 77.2% vibrissa, 12.0% guard hair, 4.5% skin, and 6.3% noxious in normal
animals). An additional 15 units were driven by a stimulating electrode
placed on the IO nerve proximal to the site of the lesion but had no
receptive field. Of the cells with vibrissa receptive fields, 33.3% were
slowly adapting type I (SAI), 6.6% were slowly adapting type II (SAII),
32.2% were low velocity rapidly adapting (RA-LV), 20.0% were high velocity
rapidly adapting (RA- HV), and 7.7% were nociceptive (NX, in normal animals
43.8% were SAI, 10.3% SAII, 27.6% RA-LV, 16.8% RA-HV, and 1.5% NX). A
number of cells had receptive field properties not seen in normal animals.
The single- unit recordings indicated that the topography of mandibular and
ophthalmic representations in the ganglion were essentially normal, while
the organization of the maxillary region of the ganglion was slightly
abnormal. The ganglion physiology experiments were augmented by records
from primary afferents in the trigeminal spinal tract (TrV). Eighty-one
(72.2%) of the 112 fibers recorded in the TrV of normal rats had IO
receptive fields. Of these, 73.2% responded to innocuous vibrissal
stimulation, 14.6% to guard hair deflection, 8.5% to gentle indentation of
the skin, and 2.5% to noxious stimuli. Of the 61 vibrissa units, 37.8% were
SAI, 19.7% SAII, 37.8% RA-LV, 3.3% RA-HV, and 1.6% NX. In adult-lesioned
animals, 81 (61.3%) of the recorded fibers had IO receptive fields. Of this
number, 38.2% responded to vibrissae, 29.6% to guard hairs, 16.0% to skin,
and 19.7% to noxious simuli. Of the vibrissa-sensitive units, 16.1% were
SAI, 3.2% were SAII, 45.2% were RA-LV, 35.5% were RA-HV, and 3.2% NX. As in
the ganglion recording studies, a number of abnormal receptive fields were
documented.(ABSTRACT TRUNCATED AT 400 WORDS)
Previous Article | Next Article
