ELECTROCHEMICAL MONITORING OF BURSTING EXOCYTOTIC EVENTS FROM THE GIANT DOPAMINE NEURON OF PLANORBIS-CORNEUS

We have discovered a neuronal system that fires bursting exocytotic ev ents. In the giant dopamine neuron of the fresh water snail Planorbis corneus, bursting exocytotic events are evoked following in situ stimu lation with elevated potassium. Amperometric detection using carbon fi ber microelectrodes, which provides high temporal resolution, has been used to record exocytotic events released from the neuron. Evaluation of the time interval between consecutive exocytotic events (inter-spi ke interval) recorded from about 80% of the neurons reveals the occurr ence of distinct bursting patterns defined by transients having an equ al interval among them. Statistical analysis of these bursting exocyto tic events shows three distinct distributions of inter-spike intervals with mid points occurring at 5, 22 and 45 ms. This bursting release b ehavior is not observed from cultured pheochromocytoma cells although they show calcium-dependent exocytosis following in situ stimulation w ith elevated potassium. Our data appear to indicate that the Planorbis dopamine neuron in vivo is actively involved in specific modes of neu ral communication and may represent an important phenomenon in underst anding single cell activities.