Observation and Quantitation of Exocytosis from the Cell Body of a FullyDeveloped Neuron in Planorbis Corneus

摘要

We have discovered a neuronal system that releases neurotransmitter viaexocytosis from the cell body. In the large dopamine cell of the pond snail Planorbis corneus, depolarization induces rhythmic release of dopamine from the cell body. When a stimulant is applied extracellularly or intracellularly in situ to the cell body, transient dopamine concentration packets which appear in a bursting pattern are observed. Dopamine release is calcium dependent and release is on the time scale expected for exocytosis (2 to 4 ms rise time). Quantitation of individual events reveals an average of 818,000 molecules per exocytotic event. As many as 89,000 individual exocytotic events have been observed following a single stimulation of one cell. Neurotransmitter exocytosis from the neuronal cell body appears to represent an alternative form of neurocommunication to synaptic transmission.