Acute hypoxia differentially affects the γ‐aminobutyric acid type A receptor α1, α2, β2, and γ2 subunit mRNA levels in the developing chick optic tectum: Stage‐dependent sensitivity

This investigation analyzes the effect of an acute hypoxic treatment on the level of four (α1, α2, β2, and γ2) subunit mRNAs of the GABAA receptor in layer “i” of the developing chick optic tectum. Our results show that 1 hr of normobaric acute hypoxia significantly changes the subunit mRNA levels. Different subunit mRNAs display different sensitivity to hypoxia: α1, β2, and γ2 mRNAs are highly sensitive, whereas α2 mRNA is almost not affected. The sensitivity of the mRNA levels to hypoxia is stage dependent. The mean percentages of variation produced by the hypoxia in the level of expression of the four subunits were 20% at ED12, 5% at ED16, and only 2% at ED18. These changes in the mean percentages of expression modify the probability of coexpression. In the case of double mRNA combinations, the hypoxia produced a mean variation in the probability of coexpression of 37% at ED12, 8% at ED16, and only 4% at ED18. With regard to the triple subunit mRNAs combinations, the variations were 206% at ED12, 11% at ED16, and only 7% at ED18. The quadruple combination values were 1,500% at ED12, 21% at ED16, and only 11% at ED18. This study demonstrates that the subunit mRNA levels are highly sensitive during the early stages, suggesting that GABAA receptor composition might undergo environment-dependent plastic changes providing a high degree of plasticity to the GABA neurotransmitter system development. © 2007 Wiley-Liss, Inc.