LAMINAR PATTERNS OF EXPRESSION OF GABA(A) RECEPTOR SUBUNIT MESSENGER-RNAS IN MONKEY SENSORY-MOTOR CORTEX

Radioactive complementary RNA probes, made from monkey-specific cDNAs specific for the alpha(1), alpha(2), alpha(4), alpha(5), beta(1), beta (2), and gamma(2) subunits of the gamma-aminobutyric acid A (GABA(A)) receptor were used for in situ hybridization histochemistry of the pri mary motor, somatosensory, and anterior parietal areas of the cerebral cortex in macaque monkeys. mRNAs for the alpha(1), beta(2), and gamma (2) subunit polypeptides, which form receptors with the full range of classical properties, are expressed at much higher levels in all areas and show laminar- and sublaminar-specific concentrations. alpha(2), a lpha(4), alpha(5), and beta(1) subunit transcripts are expressed at mu ch lower levels but also display individual, laminar-specific concentr ations; alpha(5) expression, in particular, is highly expressed in lay er IV in the somatosensory and parietal areas and in a layer IV-like b and in the motor cortex. In layers in which expression of a particular transcript is high, all neurons may express the gene, but in layers i n which expression is moderate, it is possible to detect differences i n the degree of labeling of individual neurons for a particular mRNA, and some neurons may not express certain subunit transcripts in detect able amounts. These findings indicate the variability in expression of different GABA(A) receptor subunits in the cerebral cortex. Laminar d ifferences may indicate the assembly of functional receptors from diff erent arrangements of available subunits in different classes of cells . (C) 1995 Wiley-Liss, Inc.