Studies on retinal amacrine cells using slice-patch method

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The amacrine cells are an important group of secondary neurons which can exhibit a wide variety of light-evoked responses. The main excitatory inputs to the amacrine cells are believed to originate from the bipolar cells while the amacrine cell itself is thought to provide the main inhibitory inputs to the ganglion cells. The light-evoked responses of the amacrine cells in the goldfish retina have been classified into three main groups with some subdivisions within these three main groups. As determined by intercellular recordings, amacrine cells of the goldfish retina can respond to a light stimulus by yielding a transient, a sustained depolarizing, or a sustained hyperpolarizing response. The mechanisms by which these variety of light-evoked responses is generated is still not completely understood. To elucidate some of the factors which might affect the differing responses of amacrine cells, we undertook the whole-cell patch clamp study of the amacrine cells of the goldfish retina in a slice preparation. Three main morphological subtypes of amacrine cells were observed. Four types of voltage-gated currents were identified in the amacrine cell : a sustained outward potassium current, I_K, a transient outward potassium current, I_A, a sustained inward calcium current, I_<Ca>, and a transient inward sodium current, I_<Na>. In addition, spontaneous current events, carried by chloride ions through GABA_A receptors, were recorded in most of the amacrine cells.