The expression and regulation of seven GABA(A) receptor subunit gene transcripts were examined in the adult monkey lateral geniculate nucleus. In situ hybridization histochemistry was used to localize mRNAs of the genes encoding monkey-specific ∅1, α2, α4, α5, β1, β2, and γ2 subunits. The highest levels of expression in the nucleus were for α1, β2, and γ2 subunit transcripts. The levels were substantially higher in the magnocellular than in the parvocellular layers. Alpha-2, α4, α5, and β1 subunit mRNAs were expressed at much lower levels, and magno- and parvocellular layers had approximately equal levels of expression. Following 4- or 21-day periods of monocular deprivation induced by intravitreal injections of tetrodotoxin, levels of the α1, α2, α4, α5, β1, and β2 mRNAs were decreased in the deprived geniculate laminae. Adjacent sections hybridized with probes specific for 67-kDa glutamic acid decarboxylase (GAD) mRNA also showed decreased levels of expression in deprived laminae after the 21-day deprivation period. Levels of γ2 receptor subunit mRNA were unaffected by monocular deprivation. In our previous studies, a clearly significant downregulation is observed for this subunit transcript in the visual cortex of monkeys deprived for equivalent times. The differential expression and responses to deprivation in the lateral geniculate nucleus suggest region-specific regulation of GABA(A) receptor subunit genes.
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