| Abstract: | The aim of this study is to clarify the fiber distribution of the nucleus reticularis magnocellularis (NRMC) and adjacent
areas in the rat spinal cord. Biotinylated dextran amine was injected iontophoretically through a glass capillary into the
areas, in which a single cell responded to noxious electrical stimulation of the sciatic nerve and to a pinch of the thigh
skin with multiple spikes. Labeled fibers descended bilaterally through the ventral funiculi of the medulla oblongata and
then through the ventral and lateral funiculi of the cervical cord with an ipsilateral predominance, and terminated in the
spinal gray (laminae I–2X). A single fiber sometimes ran through several laminae while bifurcating many short branches with
axon varicosities and terminal buttons in one transverse section, that is, through laminae V, VII and X, through laminae V,
III–IV and I-II, and through laminae VII to I–II. The present study showed that the wide distribution of a single fiber and
a mass of fibers descending from the NRMC and adjacent areas might modulate not only somatic sensory and motor functions but
also autonomic functions in the spinal cord. |
