The dendritic varicosity: a mechanism for electrically isolating the dendrites of cat retinal amacrine cells?

Amacrine dendritic varicosities from cat retina were reconstructed using serial electron micrographs. Each varicosity contained a synaptic input and a synaptic output, suggesting that they may function as isolated local circuits. A passive steady state electrical model demonstrated that for a given conductance change the varicose dendrite maximizes the local membrane potential and minimizes th distance membrane potential change as compared to other possible dendritic shapes. We, therefore, suggest that the function of the varicosities on amacrine cell dendrites might be to electrically isolate these local input-output circuits.