EXPRESSION OF SODIUM-CHANNEL ALPHA-SUBUNITS AND BETA-SUBUNITS IN THE NERVOUS-SYSTEM OF THE MYELIN-DEFICIENT RAT

Using subtype-specific riboprobes and a non-isotope in situ hybridizat ion technique, the pattern of expression of the mRNAs for voltage depe ndent sodium channel cr-subunits I, II, III and NaG, and the beta(1)-s ubunit were compared in myelin-deficient rats and unaffected male litt ermates. Tissues examined included the hippocampus, cerebellum, spinal cord and dorsal root ganglia. Previous studies have demonstrated that the expression of sodium channel alpha- and beta(1)-subunits follows a distinct temporal and spatial pattern during development, characteri zed in part by greater expression of alpha-subunit III and its mRNA du ring development than in the adult. We examined animals of 20-22 days of age, a time when, according to earlier reports, the unaffected anim als should nearly have reached an adult expression pattern. Normal mal e littermates were indeed found to express a sodium channel subunit mR NA pattern generally consistent with previous reports on adult rats. M yelin-deficient animals exhibited an expression pattern identical to t he unaffected littermates, indicating that myelination is not required for the progression from the embryonic to the adult expression patter n of sodium channel subunits.