Journal of Neuroscience, Vol 6, 3706-3720, Copyright © 1986 by Society for Neuroscience
Functional consequences of neonatal infraorbital nerve section in rat trigeminal ganglion
MF Jacquin, WE Renehan, BG Klein, RD Mooney and RW Rhoades
Standard single-unit recording and stimulation techniques were used to
assess the topographic organization, receptive field properties, and
projections of cells (n = 297) in the ophthalmic-maxillary part of the
trigeminal ganglion in 6 normal adult rats and 15 adults with unilateral
infraorbital nerve section at birth (cells recorded ipsilateral to lesion:
n = 641; cells recorded on the intact side: n = 223). Stimulating
electrodes were placed on the central portion of the regenerate
infraorbital nerve and in the trigeminal brain stem subnucleus caudalis in
6 nerve-damaged rats and at equivalent points in 5 normal animals. Data
from the normal rats and the intact side of the nerve-damaged animals were
identical and were considered together. Of these cells, 73.5% had
infraorbital receptive fields. Of these, 77.2% were discharged by vibrissa
stimulation (43.8% slow-adapt type I, 10.3% slow-adapt type II, 27.6%
low-velocity sensitive rapid adapt, 16.8% high-velocity sensitive rapid
adapt, and 1.5% noxious-biased), while the rest responded best to guard
hair deflection (12.0%), gentle skin indentation (4.5%), or a strong pinch
or deep pressure (6.3%). In stereotaxically matched penetrations in ganglia
ipsilateral to the neonatal infraorbital nerve lesions, only 40.6% of the
cells had infraorbital receptive fields. Of these, only 37.7% responded to
vibrissa stimulation (29.8% slow-adapt type I, 1.2% slow-adapt type II,
2.2% low-velocity sensitive rapid adapt, 32.9% high-velocity sensitive
rapid adapt, 33.9% noxious). Other infraorbital cells responded best to
guard hair deflection (11.9%), gentle skin indentation (10.8%), or a strong
pinch or deep pressure (39.6%). An additional 30 cells did not have a
detectable receptive field and were identified only by infraorbital and
brain-stem shocks. We also recorded cells with unusual infraorbital
receptive fields: 9 units responded to more than 1 vibrissa, 4 were
activated by both vibrissa and guard hair deflection, 10 had unusually
large skin or deep receptive fields, 1 had a split receptive field, and 7
were discharged only by deep pressure to the region of the nerve section.
Seven cells with infraorbital receptive fields were not driven by
infraorbital shocks, and 2 were not activated by brain-stem shocks. In
normal rats, all cells with infraorbital receptive fields were driven by
both electrodes. The percentages of receptive field types for
noninfraorbital cells were unchanged in ganglia ipsilateral to the damaged
nerve.(ABSTRACT TRUNCATED AT 400 WORDS)