EXPRESSION OF RAF SERINE THREONINE PROTEIN-KINASES IN THE CELL-BODIESOF PRIMARY SENSORY NEURONS OF THE ADULT-RAT/

We have used immunocytochemistry to examine the distribution of raf pr otein kinases in sensory neurons of the adult rat. In lumbar and trige minal sensory ganglia, cells of all size ranges appeared to be raf imm unoreactive and this was confirmed by double labeling using subpopulat ion specific markers. Almost all cells labeled with Griffonia simplici folia IB4 (a small cell marker) or immunostained by using a large cell marker (RT97) showed raf immunoreactivity. These two markers label ce lls known to differ in their expression of neurotrophin receptors (trk ). Thus raf kinases are not confined to cells expressing only certain trk subtypes. In the dorsal horn of the spinal cord, raf immunoreactiv ity was present in scattered neurons. However, sensory axons identifie d by IB4 histochemistry were devoid of raf immunostaining. Lectin-labe led nerve fibers in the cornea, lower lip and glans penis were also no t immunoreactive. Ligation of the sciatic nerve did not produce any ac cumulation of raf immunoreactivity, confirming that raf kinases are no t axonally transported to the peripheral processes of sensory neurons. Surgical dissection of the sciatic nerve caused the normal homogeneou s cytoplasmic raf immunoreactivity to be replaced in some cells by a s taining concentrated predominantly under the plasma membrane. One poss ibility is that this represents activation of raf in these cells.