Evidence for an enhanced role of GABA inhibition in visual cortical ocular dominance of cats reared with abnormal monocular experience.

The effects of microiontophoretic bicuculline, a gamma-aminobutyric acid (GABA) antagonist, on the ocular dominance of visual cortical neurons were compared in normal cats and cats reared with abnormal monocular visual experience (monocular deprivation, surgical strabismus, and monocular deprivation after dark rearing). Cells that were monocular prior to drug application showed disinhibitory effects on ocular dominance far more frequently than originally binocular cells in all rearing conditions. When the total population of neurons was considered there were marked differences among rearing conditions: only 17% of cells showed change in ocular dominance in normal cats whereas over 50% showed changes in cats reared with abnormal monocular visual experience. These results indicate that GABA inhibition plays an enhanced role in cats with abnormal cortical ocular dominance. The results are interpreted in the context that the GABA system is passively biased by alterations in the pattern of excitatory input to contribute to abnormal patterns of ocular dominance.