Partition of transient and sustained inhibitory glycinergic input to retinal ganglion cells

Physiological and pharmacological properties of possible subtypes of the native glycine receptor were investigated in retinal neurons using whole-cell voltage-clamp techniques. Two discrete inhibitory glycine responses were identified in ganglion cells. The responses could be distinguished pharmacologically: one was sensitive to strychnine and the other to 5,7-dichlorokynurenic acid. The two responses had different kinetics: the former had a fast onset and fast desensitization, whereas the latter had a slower onset and was much more sustained. The physiological and pharmacological distinctions suggest that the responses are mediated by different receptors. These receptors transduce glycinergic synaptic signals to ganglion cells, where they serve as low- and high-pass filters, respectively, of EPSPs.