Co-localization of the glial cell line-derived neurotrophic factor (GDNF) and its functional receptor c-RET was examined immunohistochemically in the dorsal root ganglion (DRG) of the 5th lumbar nerve in rats. The total 1728 DRG neurons were observed in three female rats (Wistar) with ca. 200 g body weight, 46.6% of small neurons, 41.4% of medium-sized neurons, and 8.4% of large neurons showed GDNF-immunoreactivity. C-RET immunoreactivity was more intense in small and medium-sized DRG neurons than in large ones; it was detected in 43.8% of small neurons, 52.0% of medium-sized neurons and 14.5% of large neurons. On examination of alternate serial sections, each of which was immunostained for GDNF and c-RET, 16.1% of small neurons, 16.9% of medium-sized neurons, and 2.4% of large neurons showed both GDNF- and c-RET-immunoreactivities. Ligation of the sciatic nerve caused an accumulation of GDNF immunoreactive products more prominently in the ganglion side rather than the peripheral side of ligation. Our present results suggested that GDNF was always expressed in DRG neurons and was transported to spinal dorsal horn via the primary afferent neurons. Copyright (C) 1999 Elsevier Science Ireland Ltd.
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