GABA(B) RECEPTOR GENE-EXPRESSION IN MONKEY THALAMUS

Expression of gamma-amino butyric acid type B (GABA(B)) receptor gene transcripts was examined in the macaque monkey thalamus by in situ hyb ridization, using monkey-specific cRNA probes. GABA(B) transcript expr ession was widespread and of much higher density in the dorsal thalamu s than in the reticular nucleus and other parts of the ventral thalamu s and was highest in the epithalamus. In the dorsal thalamus, highest mRNA levels were found in the anteroventral nucleus and in the parafas cicular nucleus. Sensory relay nuclei showed moderate GABA(B) mRNA lev els. Neurons of all sizes mere labeled, suggesting expression in relay cells and interneurons, and there was no labeling of neuroglial cells . Following 10-day periods of monocular deprivation, levels of GABA(B) mRNA were decreased in the deprived magno- and parvo-cellular laminae of the dorsal lateral geniculate nuclei, indicating activity-dependen t regulation. High levels of GABA(B) receptors in the dorsal thalamus are likely to reflect the high density of synaptic inputs from the ret icular nucleus while low expression in the reticular nucleus implies w eak, GABA(B)-mediated intrareticular inhibition. (C) 1998 Wiley-Liss, Inc.