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Quantitative analysis of central terminal projections of visceral and somatic unmyelinated (C) primary afferent fibers in the guinea pig
Author(s) -
Sugiura Y.,
Terui N.,
Hosoya Y.,
Tonosaki Y.,
Nishiyama K.,
Honda T.
Publication year - 1993
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.903320305
Subject(s) - lamina , neuropil , anatomy , biology , spinal cord , afferent , ganglion , lateral funiculus , somatic cell , neuroscience , dorsum , central nervous system , biochemistry , gene
In guinea pigs, intracellular labeling of the dorsal root ganglion (DRG) cells with Phaseolus vulgaris ‐leucoagglutinin (PHA‐L) was used to demonstrate the central projections of somatic and visceral afferent C‐fibers. The terminations of the afferent fibers were analyzed qualitatively and quantitatively with the aid of camera lucida drawings. Terminal branches of C‐fibers of both somatic and visceral origin were, in general, distributed in accord with the organization of the neuropil in lamina of the spinal cord. Terminal boutons arranged from longitudinally coursing fibers were distributed in lamina I, while boutons in lamina II were scattered in an apparent random fashion. The synaptic enlargements were counted in gray matter of the spinal dorsal horn and measured on each terminal branch of a fiber. All synaptic boutons (over one thousand) of somatic fibers were found in the superficial dorsal horn (laminae I and II). More than 60% of the synaptic enlargements of the visceral afferents also were localized superficially (lamina I and adjacent dorsal funiculus) while 10–20% of the visceral enlargements appeared in deeper layers of the spinal cord. Boutons of somatic C‐fibers were larger than those of visceral orgin. Quantitative data of the unmyelinated afferent fibers are discussed in the context of the sensory functions of myelinated afferent fibers. © 1993 Wiley‐Liss, Inc.