We have used sequence-specific oligonucleotide probes and in situ hybridisation histochemistry to examine the distribution of the GABAA receptor alpha 1- and gamma 2-subunit mRNAs in serial sections of 1-day-old chick brain. Both transcripts are present together, at high levels, in many brain regions. Differences are found, however, in the relative amounts of these mRNAs in two isthmic nuclei of the optic lobe, the deep cerebellar nuclei, and the dorsal thalamus. We therefore conclude that while the alpha 1 and gamma 2 subunits predominantly occur together in the same receptor complex, they may also be found separately in other GABAA receptor subtypes
