Contribution of inhibitory mechanisms to the orientation sensitivity of cat dLGN Neurones.

The effect of iontophoretically applied bicuculline methiodide, an antagonist of GABA-mediated inhibition, was tested on the responses of cat dLGN neurones to moving lines. Most geniculate neurones normally show an orientation bias when tested with slowly moving long lines. This sensitivity to the orientation of the line stimulus could be markedly reduced during iontophoretic application of bicucullin. It is concluded that the orientation bias shown by geniculate neurones is to a large extent due to intrageniculate GABAergic inhibition.