Differential distribution of gamma-aminobutyric acid(A) receptor subunit (alpha(1), alpha(2), alpha(3), alpha(5) and beta(2+3)) immunoreactivity in the medial prefrontal cortex of the rat

A detailed mapping of the gamma-aminobutyric acid (GABA)(A) receptor subunits (alpha(1), alpha(2), alpha(3), alpha(5) and beta(2+3)) in the infralimbic/ventral prelimbic region (IL/vPL) of the rat frontal cortex was carried out using subunit-specific antibodies. The alpha(1) and beta(2+3) subunit antibodies immunostained all layers of the IL/vPL region. Layers II and III displayed immunostaining of cell bodies whereas I, V and VI showed predominantly neuropil staining. The size of the alpha(1)-positive cell bodies corresponded to that of small interneurons (range, 20-55 mu m(2), mean +/- SEM, 37 +/- 5.5 mu m(2)) as well as pyramidal cells or large interneurons (range, 87-135 mu m(2); mean +/- SEM, 103.4 +/- 9.7 mu m(2)). However, beta(2+3) antibody immunostained only small cell bodies. Immunoreactivity for alpha(2) was restricted to layers I and II, whereas alpha(3) and alpha(5) subunit expression was seen only in layer VI. The antibody to the at subunit immunostained small cell bodies (range, 29-63 63 mu m(2); mean +/- SEM, 32 +/- 4.5 mu m(2)) in layer II, resembling interneurons. Conversely, both alpha(3) and alpha(5) antibodies immunostained large cell bodies (range, 94-151 mu m(2); mean +/- SEM, 115.7 +/- 13.4 mu m(2)), consistent with pyramidal cell labelling in layer VI.