DESCRIPTION (From the Applicant's Abstract): The goal of this study is to determine whether amacrine cells (ACs) of different morphology and neurotransmitter content exhibit different light response characteristics such as response polarity, kinetics, relative excitatory/inhibitory inputs, relative rod/cone inputs and the frequency of spontaneous postsynaptic current events. Although 20-30 types of anatomically distinct ACs have been reported, the correlation between cell morphology, neurotransmitter content and light responses has not been well established. A recent study has shown that there are twelve types of bipolar cells in the salamander retina, each has distinguishable light response characteristics and pattern of axon terminal stratification in the IPL. It is important to determine how these functionally and morphologically segregated bipolar cell signals are transmitted to the ACs and how ACs integrate and/or segregate these bipolar cell inputs. My specific aim 1 is to correlate light response characteristics with cell morphology of ACs by whole-cell voltage clamp and Lucifer yellow fluorescence with confocal microscopy. My specific aim 2 is to correlate light responses, morphology and neurotransmitter content of individual ACs by using double labeling techniques. In this way, I plan to construct a comprehensive map of how patterns of dendritic stratification in the IPL and the cells' neurotransmitter content are correlated with various light response parameters in individual ACs.