DIFFERENTIAL EXPRESSION OF SODIUM-CHANNELS IN ACUTELY ISOLATED MYELINATING AND NON-MYELINATING SCHWANN-CELLS OF RABBITS

1. Single channel recordings were made of voltage-sensitive sodium cha nnels in outside-out patches excised from the cell body region of Schw ann cells. The cells were freshly isolated from sciatic nerves of 10-w eek-old rabbits and both myelinating and non-myelinating Schwann cells were visually identified for recordings. 2. Sodium channel activities were observed in approximately 75 % of patches (n = 41) obtained from cell bodies of non-myelinating Schwann cells. In contrast. sodium cha nnels were not observed in patches (n = 78) obtained from cell bodies of myelinating Schwann cells. 3. Transection of the sciatic nerves and allowing Wallerian degeneration to occur for 5-11 days in vivo prior to recording resulted in the appearance of sodium channel activities i n approximately 30% of the patches (n = 33) obtained from the cell bod y of the myelinating cells. 4. It is interesting that although immunoc ytochemical and saxitoxin binding experiments indicate the clear prese nce of sodium channels in the plasmalemma of myelinating Schwann cells (both at the cell body and at the paranodal region), the present stud y suggests that these channels are absent from the soma region of norm al myelinating Schwann cells.