TYPE-II SODIUM-CHANNELS IN SPINAL-CORD ASTROCYTES IN-SITU - IMMUNOCYTOCHEMICAL OBSERVATIONS

The expression of sodium channel alpha-subunit isoforms in astrocytes in adult rat spinal cord and optic nerve was examined utilizing immuno cytochemical methods with antibodies generated against conserved and s ubtype-specific sequences of the sodium channel. In adult rat spinal c ord, astrocytes within the dorsal and ventral funiculi were immunolabe lled with antibody SP20, which recognizes a conserved sequence within sodium channel types I, II, and III. In addition, astrocytes within th ese spinal cord white matter tracts were immunostained with antibody S P11-II, which recognizes sodium channel type II. Antibodies SP11-I and SP32-III, which are directed against subtype-specific sequences in so dium channel types I and III, respectively, did not label astrocytes i n the dorsal and ventral funiculi of the spinal cord. In optic nerves, astrocytes were immunostained with antibody SP20. However, no detecta ble labelling of cells within the optic nerve was observed with antibo dies SP11-I, SP11-II, and SP32-III. These observations demonstrate tha t sodium channel II is expressed by astrocytes in spinal cord white ma tter. Moreover, these data suggest that regional factors regulate the level of sodium channel isoform expression in astrocytes. (C) 1994 Wil ey-Liss, Inc.