We have evaluated the spatial distribution of low-voltage-activated
calcium currents in ganglion cells of the tiger salamander retina.
Whole-cell recordings were obtained from ganglion cells in a retinal
slice preparation and from acutely dissociated ganglion cells that were
identified through retrograde dye injection. In single dissociated
cells, we estimated the magnitude (pA) and current density (pA/pF)
of LVA currents in ganglion cells, both with and without dendritic
processes. Ganglion cells that retained a portion of their dendritic
arbor had larger LVA calcium currents and higher LVA current densities
than those which lacked processes. When cell capacitance measurements
were used to derive the surface area of the soma and dendritic
processes, we concluded that a higher LVA current density was present
in the dendrites; we estimate that, on average, the current density in
the dendrites is approximately five times that of the soma. The
presence of a significant density of LVA calcium channels in the
dendrites of ganglion cells suggests that they could be involved in a
number of cellular functions, including dendritic integration of
synaptic currents, impulse generation, and homeostatic functions
related to changes in the intradendritic calcium concentration.