Eur J Anat, 1 (1): 43-50 (1997)

Distribution of the a₁, a₂ and B_2/3 GABA_A receptor subunits in the anterior thalamus of the rat

Héctor J. Caruncho, Isabel Liste and José Luis Labandeira-García*

*- Dept. of Morphological Sciences. University of Santiago de Compostela. School of Medicine, E-15705 Santia­go de Compostela. Spain.

ABSTRACT The distribution of the al' a2 and ~2/3subunits of the GABAA receptor in the anterior thalamus of the rat was studied by immunocytochemistry using subunit-specific antibodies. In general, though with some exceptions, immunoreactivity was observed mostly in the neuropil. Most prin­ cipal (relay) thalamic nuclei showed strong al and ~2/3-positivity; however, most intralaminar nuclei were immunonegative for these subunits. The reverse was true of a? immunoreactivity: most intralaminar nuclei were strongly a?-positive, whereas most principal nuclei were cl?-nega­ tive or only weakly immunopositive. These data suggest that neurons in the principal nuclei mostly express GABAA receptors containing the aland ~2! subunits (i.e. benzodiazepine type 1 receptors), while neurons in the intralaminar nu­ clei mostly express GABAA receptors containing the a? subunit (i.e. benzodiazepine type II re­ ceptors). Double-Iabeling experiments revealed colocalization of the al and ~2/3 subunits insomata and neurites of most principal nuclei. Colocalization of the al and a2 subunits was observed only in neurons of the anterodorsal nucleus.

Keywords: Thalamus, GABAA receptor, immunocytochemistry, rat.