Ja. Black et al., ISOFORM-SPECIFIC EXPRESSION OF SODIUM-CHANNELS IN ASTROCYTES IN-VITRO- IMMUNOCYTOCHEMICAL OBSERVATIONS, Glia, 14(2), 1995, pp. 133-144
The expression of sodium channel alpha-subunit isoforms in astrocytes
cultured from P-0 rat spinal cord and P-7 rat optic nerve was examined
utilizing immunocytochemical methods with antibodies generated agains
t conserved and isoform-specific amino acid sequences of the rat brain
sodium channel. In spinal cord cultures at 5 days in vitro (DIV), bot
h stellate and flat astrocytes were immunostained with antibody SP20,
which recognizes a conserved sequence common to sodium channel types I
, II/IIA, and III. Antibody SP11-I, which is directed against a subtyp
e-specific sequence in sodium channel I, did not yield detectable stai
ning in spinal cord astrocytes. Antibody SP11-II, which is directed ag
ainst a subtype-specific sequence in sodium channel II, immunostained
both stellate and flat spinal cord astrocytes, although with less inte
nsity than SP20. Antibody SP32-III, which is directed against a subtyp
e-sequence in sodium channel III, immunostained stellate but not flat
spinal cord astrocytes. SP20, SP11-II, and SP32-III staining persisted
in stellate spinal cord astrocytes through 14-21 DIV, while SP20 and
SP11-II immunostaining in flat spinal cord astrocytes was attenuated w
ith time in culture. In optic nerve cultures at 5 DIV, SP20 staining w
as present in both stellate and flat astrocytes, but at reduced levels
compared to spinal cord astrocytes. With increased time in culture, S
P20 staining was maintained in stellate optic nerve astrocytes but was
gradually lost in flat optic nerve astrocytes. Stellate optic nerve a
strocytes exhibited low levels of staining with SP11-I, SP11-II, and S
P32-III. Flat optic nerve astrocytes lacked or displayed very low SP11
-II staining, and SP11-I and SP32-III staining was not detectable. The
se observations demonstrate that cultured astrocytes are immunoreactiv
e to antibodies generated against conserved and isotype-specific pepti
de sequences of rat brain sodium channels, and further suggest that th
ere are different patterns of sodium channel expression between flat v
s. stellate astrocytes and in astrocytes derived from different region
s of the CNS. (C) 1995 Wiley-Liss, Inc.