Synapsin I in Nerve Terminals: Selective Association with Small Synaptic Vesicles

Immunocytochemistry revealed that synapsin I is preferentially (and possibly exclusively) associated with small (40- to 60-nanometer) synaptic vesicles and not with large (greater than 60-nanometer) dense-core vesicles in bovine hypothalamus. These observations may explain why synapsin I is found exclusively in neurons, since small synaptic vesicles are specific to neurons whereas large densecore vesicles in neurons may be considered the equivalent of secretory organelles in endocrine cells.