Action potentials in the dendrites of retinal ganglion cells

The somas and dendrites of intact retinal ganglion cells were exposed by en zymatic removal of the overlying endfeet of the Muller glia. Simultaneous w hole cell patch recordings were made from a ganglion cell's dendrite and th e cell's soma. When a dendrite was stimulated with depolarizing current, im pulses often propagated to the soma, where they appeared as a mixture of sm all depolarizations and action potentials. When the soma was stimulated, ac tion potentials always propagated back through the dendrite. The site of in itiation of action potentials, as judged by their timing, could be shifted between soma and dendrite by changing the site of stimulation. Applying QX- 314 to the soma could eliminate somatic action potentials while leaving den dritic impulses intact. The absolute amplitudes of the dendritic action pot entials varied somewhat at different distances from the soma, and it is not clear whether these variations an real or technical. Nonetheless, the qual itative experiments clearly suggest that the dendrites of retinal ganglion cells generate regenerative Na+ action potentials, at least in response to large diner depolarizations.