Effect of prolonged hypoxia on Na + channel mRNA subtypes in the developing rat cortex

Voltage-gated Na + channels are regulated in response to oxygen deprivation in the mammalian cortex. Past investigations have demonstrated that Na + channel protein expression is up-regulated in the immature brain exposed to prolonged hypoxia. Since it is unknown as to which Na + channel subtype(s) is involved in this regulation, we used RT-PCR to assess the effect of hypoxia on Na + channel I, II and III α-subunit mRNA expression in the developing rat cortex. Na + channel II mRNA tended to increase during early development, whereas Na + channel I and III did not change or slightly decreased with age. Hypoxic exposure for 1-day had no effect on Na + channel expression, while 5-day hypoxia significantly increased Na + channel III density, with a slight increase in Na + channel I and no appreciable change in Na + channel II. These results suggest that Na + channel subtype expression in the developing cortex is differentially regulated in response to prolonged hypoxic exposure.