Journal of Neuroscience, Vol 8, 2234-2247, Copyright © 1988 by Society for Neuroscience
Effect of neonatal infraorbital nerve transection on substance P- and leucine enkephalin-like immunoreactivities in trigeminal subnucleus caudalis of the rat
RW Rhoades, NL Chiaia, PR Hess and MW Miller
Department of Anatomy, University of Medicine and Dentistry of New Jersey, School of Osteopathic Medicine, Piscataway 08854.
The distributions of substance P-like immunoreactivity (SPLI) and
leucine-enkephalin-like immunoreactivity (LENKLI) in subnucleus caudalis of
normal adult rats were compared with those observed in the adult rats that
sustained transection of the infraorbital (IO) nerve either on the day of
birth or in adulthood. All immunocytochemical experiments in the neonatally
nerve damaged rats were carried out at least 60 d after the nerve
transection. In the animals that sustained nerve transections as adults,
brains were processed for immunohistochemistry between 7 and 60 d after the
lesions. In the rats that sustained IO nerve transections as adults, there
was a transient reduction in the density of the SPLI in layers I and II of
ipsilateral subnucleus caudalis. It was most apparent about 2 weeks after
the nerve transection and returned to near normal values by 60 d after the
lesion. In the rats that sustained IO nerve transections on the day of
birth, there was no reduction in the density of SPLI in caudalis, and the
band of staining on the deafferented side of the brain stem was actually
40% wider than that on the intact side. Neither neonatal nor adult IO nerve
transection had appreciable effects upon the distribution of LENKLI in the
rat's trigeminal brain-stem complex. In another series of experiments, rats
that sustained neonatal transection of the IO nerve had this same nerve
recut in adulthood. Twelve days after the second lesion, the brains of
these animals were processed for SPLI. There was a marked reduction in the
density of the staining for this peptide on the deafferented side. This
last result is consistent with the interpretation that the increased
distribution of SPLI in the neonatally nerve damaged rats is due, at least
partially, to reorganization of primary afferents.