Electrochemical monitoring of bursting exocytotic events from the giant dopamine neuron of Planorbis corneus.

We have discovered a neuronal system that fires bursting exocytotic events. In the giant dopamine neuron of the fresh water snail Planorbis corneus, bursting exocytotic events are evoked following in situ stimulation with elevated potassium. Amperometric detection using carbon fiber 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-spike interval) recorded from about 80% of the neurons reveals the occurrence of distinct bursting patterns defined by transients having an equal interval among them. Statistical analysis of these bursting exocytotic events shows three distinct distributions of inter-spike intervals with mid points occurring at 5, 22 and 45 ms. This bursting release behavior is not observed from cultured pheochromocytoma cells although they show calcium-dependent exocytosis following in situ stimulation with elevated potassium. Our data appear to indicate that the Planorbis dopamine neuron in vivo is actively involved in specific modes of neural communication and may represent an important phenomenon in understanding single cell activities.