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Central projection of unmyelinated (C) primary afferent fibers from gastrocnemius muscle in the guinea pig
Author(s) -
Ling LiJun,
Honda Takashi,
Shimada Yasuhiro,
Ozaki Noriyuki,
Shiraishi Yousuke,
Sugiura Yasuo
Publication year - 2003
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.10619
Subject(s) - anatomy , biology , spinal cord , retrograde tracing , lamina , fasciculus , guinea pig , ganglion , lumbar , dorsal root ganglion , neuroscience , dorsum , white matter , medicine , endocrinology , fractional anisotropy , radiology , magnetic resonance imaging
We have demonstrated the central projections of muscle C or group IV afferent fibers in the guinea pig by tracing arborizations in the spinal cord. C afferent fibers from the gastrocnemius muscle (GCM) were electrophysiologically identified by conduction velocity (less than 1 m/second). A single neuron in the lumbar 5 dorsal root ganglion (L5 DRG) was intracellularly labeled with Phaseolus vulgaris leucoagglutinin (PHA‐L). After iontophoretic injection of PHA‐L, we processed the lumbar cord and L5 DRG for PHA‐L immunohistochemistry. Six muscle C afferent fibers from 40 animals were labeled, and whole trajectories were recovered. Labeled fibers were reconstructed by tracing of the arbor in serial parasagittal sections. The GCM C afferents projected rostrocaudally for two or three segments and ran at the surface of the dorsal funiculus, giving off collaterals into laminae I and II and sometimes into parts of lamina III. We determined, based on the branching pattern and form of the terminal plexus, that the branching of muscle C afferent fibers showed an intermediate pattern that fell morphologically between the terminal patterns of somatic and visceral afferents. The numbers and sizes of fiber swellings and terminal swellings were measured on all collateral branches. We found that the area of distribution of the terminal swellings of muscle C afferent fibers is larger than that of somatic terminals but that the density of terminal swellings in the terminal area was lower than that of the somatic terminals. J. Comp. Neurol. 461:140–150, 2003. © 2003 Wiley‐Liss, Inc.