Influence of GABAergic pathway on retinal adaptation-related response changes

Retinal ganglion cells （RGCs） exhibit adaptive changes in response to sustained light stimulation, which include decrease in firing rate, tendency to shrink in receptive field （RF） size and reduction in synchronized activities. Gamma-aminobutyric acid-ergic （GABAergic） pathway is an important inhibitory pathway in retina. In the present study, the effects of GABAergic pathway on the contrast adaptation process of bullfrog RGCs were studied using multi-electrode recording technique. It was found that the application of bicuculline （BIC）, a gamma-aminobutyric acid A （GABAA） receptor antagonist, caused a number of changes in the RGCs＇ response characteristics, including attenuation in adaptation-dependent firing rate decrease and the adaptation-dependent weakening in synchronized activities between adjacent neuron-pairs, whereas intensified the adaptation-dependent RF size shrinkage. These results suggest that GABAA receptors are involved in the modulation of the firing activity and synchronized activities in contrast adaptation process of the RGCs, whereas the adaptation-related RF property changes involve more complicated mechanisms.