MULTIPLE CLASSES OF CATECHOLAMINE VESICLES OBSERVED DURING EXOCYTOSISFROM THE PLANORBIS CELL BODY

The heterogeneous nature of vesicles has been studied by evaluating ex ocytotic events released from the cell body of a dopamine-containing n euron of Planorbis corneus. Vesicular exocytosis has been elicitied by stimulation with in situ application of elevated potassium and has be en monitored electrochemically with a carbon fiber microelectrode plac ed on the cell body. These electrodes allow individual release events to be monitored and quantitated to reveal vesicular dopamine content. Statistical analysis of individual release events demonstrates that tw o classes of vesicles with specific bimodal distributions in dopamine content and vesicle size are observed after cell stimulation. The effe ct of a psychostimulant on individual vesicular dopamine level has bee n studied by treating the cells with D-amphetamine. After a 20-min app lication of 10 mu M amphetamine, changes in both vesicle content and s ize distributions are obtained with an overall decrease in vesicular d opamine level. of 40%. The altered distribution show trimodal shapes i ndicating a third class of vesicles is created by amphetamine treatmen t. Our data appears to indicate that multiple classes of vesicles are released from the cell body of the dopamine-containing neuron and vesi cular dopamine level can be manipulated by the application of the lipo philic weak base amphetamine.