Primary sensory neurons with dichotomizing axons projecting to the facet joint and the sciatic nerve in rats.
METHODS
Dorsal root ganglion (DRG) neurons that have dichotomizing axons to the lumbar facet joint and to the sciatic nerve were investigated in rats using a double fluorescent labeling technique.


OBJECTIVE
To clarify the existence of DRG neurons with dichotomizing axons projecting to the lumbar facet joint and to the sciatic nerve in rats.


BACKGROUND
DRG neurons having dichotomizing axons have been reported in several species and are considered to be related to referred pain. However, such DRG neurons have not been investigated in the lumbar spine. Clinically, pain from the lumbar facet joint is sometimes referred to the lower extremities innervated by the sciatic nerve.


METHODS
Two kinds of neurotracers (DiI and FG) were used in the present double-labeling study. DiI crystals were placed in the left L5-L6 facet joint, and FG was applied to the ipsilateral sciatic nerve or along the midline of the L5 dermatome. Bilateral DRGs T13-S1 were observed by fluorescence microscope.


RESULTS
DRG neurons double labeled with DiI and FG were recognized only in the ipsilateral DRGs from L3 to L6 levels. Approximately 3% of DRG neurons innervating the L5-L6 facet joint had other axons to the sciatic nerve. By contrast, no double-labeled neurons were observed after FG was applied to the L5 dermatome.


CONCLUSIONS
In rats approximately 3% of DRG neurons innervating the lumbar facet joints have dichotomized axons projecting to the sciatic nerve.
Sameda
H
H
Third Department of Anatomy, School of Medicine, Chiba University, Japan. sameda@athena.ocn.ne.jp
Takahashi
Y
Y
Takahashi
K
K
Chiba
T
T
Ohtori
S
S
Moriya
H
H
D000818:Animals; D001369:Axons / Q000502:physiology*; D002232:Carbocyanines; D005456:Fluorescent Dyes; D005727:Ganglia, Spinal / Q000166:cytology / Q000502:physiology*; D006614:Hindlimb; D008159:Lumbar Vertebrae / Q000294:innervation*; D008297:Male; D009475:Neurons, Afferent / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012584:Sciatic Nerve / Q000502:physiology*; D012867:Skin / Q000294:innervation; D013266:Stilbamidines; D009435:Synaptic Transmission
C049774:2-hydroxy-4,4'-diamidinostilbene, methanesulfonate salt; D002232:Carbocyanines; D005456:Fluorescent Dyes; D013266:Stilbamidines; C024286:3,3'-dioctadecylindocarbocyanine