Specifically, they are thought to be involved in regulating the number of synaptic vesicles available for release via exocytosis at any one time.

Gene knockout studies in mice (where the mouse is unable to produce synapsin) have had some surprising results.

Consistently, knockout studies have shown that mice lacking one or more synapsins have defects in synaptic transmission induced by high‐frequency stimulation, suggesting that the synapsins may be one of the factors boosting release probability in synapses at high firing rates, such as by aiding the recruitment of vesicles from the reserve pool.

[4] These results suggest that while synapsins are not essential for synaptic function, they do serve an important modulatory role.

Lastly, observed effects seemed to vary between inhibitory and excitatory synapses, suggesting synapsins may play a slightly different role in each type.