Spontaneous voltage transients in mammalian retinal ganglion cells dissociated by vibration

We recently developed a new method to dissociate neurons from mammalian retinae by utilizing low-Ca2+ tissue incubation and the vibro-dissociation technique, but without use of enzyme. The retinal ganglion cell somata dissociated by this method showed spontaneous voltage transients (sVT) with the fast rise and slower decay. In this study, we analyzed characteristics of these sVT in the cells under perforated-patch whole-cell configuration, as well as in a single compartment cell model. The sVT varied in amplitude with quantal manner, and reversed in polarity around -80 mV in a normal physiological saline. The reversal potential of sVT shifted dependently on the K+ equilibrium potential, indicating the involvement of some K+ conductance. Based on the model, the conductance changes responsible for producing sVT were little dependent on the membrane potential below -50 mV. These results could suggest the presence of isolated, inhibitory presynaptic terminals attaching on the ganglion cell somata.