The expression of rat brain voltage-sensitive Na+ channel mRNAs in astrocytes.
Astrocytes from various regions of CNS have been shown to express voltage-activated Na+ currents. To date, three distinct subtypes (I, II and III) of Na+ channels have been cloned from rat brain. We have applied a combined technique of reverse transcription and polymerase chain reaction (RT-PCR) to examine the expression of rat brain Na+ channels in rat astrocytes in vivo and in vitro. Five PCR primer sets were used to amplify coding or 3' non-coding regions of subtype I, II, and III Na+ channels. We were able to amplify all three of these rat brain Na+ channel subtypes from rat optic nerve, which does not have neuronal cell bodies but does contain astrocytes known to express voltage-sensitive Na+ channels. In studies on cultured spinal cord astrocytes, we were also able to amplify all three subtypes of rat brain Na+ channel mRNAs. In control experiments, RT-PCR was performed on RNAs prepared from several rat tissues, including brain, skeletal muscle, and liver. Rat brain was shown to express the three Na+ channel subtypes as expected. In rat skeletal muscle, subtype I and III Na+ channel mRNAs, but not subtype II, were amplified. In rat liver, Na+ channel messages were not detectable. The present study provides the first direct evidence that astrocytes in vivo and in vitro express rat brain voltage-sensitive Na+ channel mRNAs, which have been considered as mainly neuronal-type Na+ channel messages.
Oh
Y
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Department of Neurology, Yale University School of Medicine, New Haven, CT 06510.
Black
J A
JA
Waxman
S G
SG
D000818:Animals; D001253:Astrocytes / Q000378:metabolism*; D001923:Brain Chemistry; D002478:Cells, Cultured; D005786:Gene Expression Regulation; D009419:Nerve Tissue Proteins / Q000096:biosynthesis* / Q000235:genetics; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D012680:Sensitivity and Specificity; D015222:Sodium Channels / Q000096:biosynthesis* / Q000145:classification / Q000235:genetics; D013116:Spinal Cord / Q000166:cytology* / Q000378:metabolism
D009419:Nerve Tissue Proteins; D012333:RNA, Messenger; D015222:Sodium Channels