Synapsím

Synapsím is a term used to describe a hypothetical class of presynaptic regulatory elements in neurons that coordinate neurotransmitter release by modulating synaptic vesicle availability and release probability at the active zone. The term is not an established scientific term; it is used in speculative literature and some fiction to discuss potential mechanisms that could couple electrical activity with rapid, multivesicular release and plastic changes at the synapse.

Possible composition and mechanism: In theoretical models, synapsím refers to a protein-like complex or signaling module that interacts with the cytoskeleton, SNARE machinery, and calcium sensors. It is proposed to respond to intracellular calcium transients, promoting rapid mobilization of reserve vesicles toward release sites or stabilizing release-ready vesicles, thereby influencing short-term synaptic plasticity such as facilitation and depression on time scales from milliseconds to seconds.

Discovery status: As of now, there is no consensus or widely accepted molecular identity for synapsím. It is often discussed as a concept to explore how synaptic regulation could operate beyond classic paradigms like synapsins and release probability modulation. Some researchers note that components resembling the proposed functions might exist in known proteins, but no definitive evidence confirms a distinct synapsím system.

See also: synapse, synaptic plasticity, synapsin, presynaptic active zone, vesicle trafficking.