Differential distribution of γ-aminobutyric acidA, receptor subunit (α1, α2, α3, α5 and β2+3) immunoreactivity in the medial prefrontal cortex of the rat

Abstract A detailed mapping of the γ-aminobutyric acid (GABA) A receptor subunits ( α 1 , α 2 , α 3 and β 2+3 ) in the infralimbic/ventral prelimbic region (IL/vPL) of the rat frontal cortex was carried out using subunit-specific antibodies. The α 1 and β 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 α 1 -positive cell bodies corresponded to that of small interneurons (range, 20–55 μm 2 ; mean ± SEM, 37 ± 5.5 μm 2 ) as well as pyramidal cells or large interneurons (range, 87–135 μm 2 ; mean ± SEM, 103.4 ± 9.7 μm 2 ). However, β 2+3 antibody immunostained only small cell bodies. Immunoreactivity for α 2 was restricted to layers I and II, whereas α 3 and α 5 subunit expression was seen only in layer VI. The antibody to the α 2 subunit immunostained small cell bodies (range, 29–63 μm 2 ; mean ± SEM, 32 ± 4.5 μm 2 ) in layer II, resembling interneurons. Conversely, both α 3 and α 5 antibodies immunostained large cell bodies (range, 94–151 gmm 2 ; mean ± SEM, 115.7 ± 13.4 μm 2 ), consistent with pyramidal cell labelling in layer VI.