STARBURST AMACRINE CELLS CHANGE FROM SPIKING TO NONSPIKING NEURONS DURING RETINAL DEVELOPMENT

The membrane excitability of cholinergic (starburst) amacrine cells wa s studied in the rabbit retina during postnatal development. Whole-cel l patch-clamp recordings were made from 110 displaced starburst cells in a thin retinal slice preparation of rabbits between postnatal days P1 acid P56 old. We report that displaced starburst cells undergo a dr amatic transition from spiking to nonspiking, caused by a loss of volt age-gated Na currents. This change in membrane excitability occurred j ust after eye opening (P10), such that all of the starburst cells test ed before eye opening had conspicuous tetrodotoxin-sensitive Na curren ts and action potentials, but none tested after the first 3 postnatal weeks had detectable Na currents or spikes. Our results suggest that s tarburst cells use action potentials transiently during development an d probably play a functional role in visual development. These cells t hen cease to spike as the retina matures, presumably consistent with t heir role in visual processing in the mature retina.