Presynaptiset

Presynaptiset is a term used in some neuroscience discussions to refer to the presynaptic apparatus of chemical synapses—the structures and processes that control the release of neurotransmitters from the presynaptic neuron. It encompasses the cellular components and molecular machinery that operate at the axon terminal to enable synaptic transmission.

Key components include the presynaptic terminal (bouton) and the active zone, where vesicle docking occurs, as well as the molecular machinery that mediates vesicle fusion. This includes synaptic vesicles, SNARE proteins (syntaxin-1, SNAP-25, and synaptobrevin/VAMP), and the calcium sensor synaptotagmin, as well as voltage-gated calcium channels (P/Q-type Cav2.1 and N-type Cav2.2) that mediate calcium influx. The coordinated action of these elements enables fast, calcium-triggered exocytosis of neurotransmitters into the synaptic cleft.

During the vesicle cycle, vesicles originate from multiple pools, are docked and primed at the active zone, and released when Ca2+ triggers SNARE-mediated fusion. After neurotransmitter release, endocytosis via clathrin-coated pits recovers vesicles for recycling, helping to maintain the readily releasable pool and sustain transmission during activity.

Release probability and timing are modulated by presynaptic receptors and signaling pathways. Autoreceptors and neuromodulators adjust calcium entry and SNARE activity through kinases and phosphatases, contributing to short-term plasticity such as facilitation and depression, and affecting long-term synaptic strength.

Presynaptiset thus captures the functional core of neurotransmitter release and its regulation, with implications for learning, memory, and neurological disorders. While the term is not universally used, it aligns with established concepts of presynaptic terminals and their role in neural circuitry.