Expression of α3, β3 and γ1 GABAA receptor subunit messenger RNAs in visual cortex and lateral geniculate nucleus of normal and monocularly deprived monkeys

Complementary RNA probes derived from complementary DNA specifically subcloned from monkey tissue were used to localize, by in situ hybridization histochemistry, the relatively rare α3, β3 and γ1 subunit transcripts of the GABAA receptor in visual cortex and lateral geniculate nucleus of normal monkeys and in monkeys that had been deprived of vision in one eye. Overall, levels of α3, β3 and γ1 subunit transcripts were very low. In the primary visual cortex (area 17) they were concentrated in layers II and VI and in a stratum of white matter subjacent to layer VI. The localization and density of the three messenger RNAs closely resembled those of other rare (α2, α5 and β1) transcripts but their distribution also overlapped that of the predominant α1, β2 and γ2 subunit transcripts. In area 18, α3 and β3 transcript distribution resembled that in area 17, with the addition of a third band of hybridization in layer IV for β3. γ1 subunit transcript localization in area 18 differed significantly from that in area 17, with increased expression restricted to layer IV. In the dorsal lateral geniculate nucleus, β3 and γ1 transcripts were expressed at low levels across all layers while α3 transcripts were restricted to the magnocellular layers. Following 15 and 18 day periods of monocular deprivation, induced by intravitreal injections of tetrodotoxin, levels of α3 receptor subunit transcripts showed modest reductions in layer VI of area 17 and in deprived geniculate laminae of adult animals. Reductions in α3 transcript levels were much more pronounced in layer IVCβ of a five-month-old monkey deprived for the same time. Levels of β3 and γ1 transcripts were unaffected by monocular deprivation in cortex and geniculate at any age.