We assessed the mechanisms and related kinetics of vesicular release during the enhancement and depression of synaptic efficacy by the exogenous application of neuromodulators as well as altering the levels of protein related to vesicle fusion within nerve terminals. In order for a vesicle to be released, it must first dock at the presynaptic membrane; then, in the presence of Ca2+, a fusion pore for evoked transmitter release opens. To determine if the presence of synaptically relevant proteins, such as α-SNAP, can alter the number of evoked quantal units and then-rate of occurrence, α-SNAP was injected into the nerve terminals and the kinetics of release were measured. The enhancement of α-SNAP within the nerve terminal increases the number of rapidly occurring quantal events. The neuromodulator serotonin (5-HT), known to stimulate an IP3 cascade, also causes an enhancement of evoked quantal events. The presence of 5-HT or ot-SNAP at the terminal results in a faster rate of release for multiple events without a detectable change in the initial rate of primary events. Interestingly, the molt-related hormone, ecdysone (20-HE), causes a decrease in the rate of multiple events and results in an increase in latency jitter of vesicular release, thus indicating that 20-HE may act as a neuromodulator that depresses release. Investigating proteins and modulators of synaptic function will hopefully allow one to understand some of the mechanisms underlying synaptic differentiation and selective actions of neuromodulators, individually and in combination.