EFFECT OF SENSORY DEAFFERENTATION ON IMMUNOREACTIVITY OF GABAERGIC CELLS AND ON GABA RECEPTORS IN THE ADULT CAT VISUAL-CORTEX

To investigate the effects of sensory deafferentation on the cortical GABAergic circuitry in adult cats, glutamic acid decarboxylase (GAD) a nd gamma-aminobutyric acid (GABA) immunoreactivity and GABA receptor b inding were studied in the visual cortex of normal cats and compared w ith cats that had received restricted binocular central lesions of the retina and had survived for 2 weeks postlesion in a normal visual env ironment. In the visual cortex of lesioned cats, two changes were obse rved in the number of GAD-immunoreactive elements in the regions affec ted by the retinal lesions: the number of GAD-positive puncta decrease d, whereas that of GAD-immunoreactive somata increased. In contrast, n o detectable changes were measured in the number of GABA-immunopositiv e somata or puncta. At the receptor level, we observed no differences in either the laminar distribution or the affinity of cortical GABAA a nd GABAB receptors labeled with [H-3]muscimol and [H-3]-baclofen, resp ectively, in the lesioned versus normal cats. We present the hypothesi s that sensory deafferentation in these adult cats (1) leads to a redu ction of cortical GABAergic inhibition in the deafferented region, and (2) that this decreased inhibition may permit changes in efficiency o f synapses and (3) that these changes may represent a first stage of e vents underlying the retinotopic reorganization preceeding the structu ral changes. (C) 1995 Wiley-Liss, Inc.