A crucial problem in neurotransmitter release is how the fusion pore regulates the amount of cargo released during exocytosis. Vesicles can either merge with the plasma membrane (full vesicle fusion) or they can release part of their neurotransmitters during transient contacts (kiss-and-run events). From a lipocentric point of view, after the first aqueous connection, fusion pores have been observed to either close or expand towards a metastable state. 12,82