Perisynaptic schwann cells

Perisynaptic schwann cells (also known as Terminal schwann cells or Teloglia) are neuroglia found at the Neuromuscular junction (NMJ) with known functions in synaptic transmission, synaptogenesis, and nerve regeneration. These cells share a common ancestor with both Myelinating and Non-Myelinating Schwann Cells called Neural Crest cells. Perisynaptic Schwann Cells (PSCs) contribute to the tripartite synapse organization in combination with the pre-synaptic nerve and the post-synaptic muscle fiber. PSCs are considered to be the glial component of the Neuromuscular Junction (NMJ) and have a similar functionality to that of Astrocytes in the Central Nervous System. The characteristics of PSCs are based on both external synaptic properties and internal glial properties, where the internal characteristics of PSCs develop based on the associated synapse, for example: the PSCs of a fast-twitch muscle fiber differ from the PSCs of a slow-twitch muscle fiber even when removed from their natural synaptic environment. PSCs of fast-twitch muscle fibers have higher Calcium levels in response to synapse innervation when compared to slow-twitch PSCs. This balance between external and internal influences creates a range of PSCs that are present in the many Neuromuscular Junctions of the Peripheral Nervous System.

Discovery

Perisynaptic (Terminal) Schwann Cells were first discovered by Louis-Antoine Ranvier in 1878 when he observed branching networks surrounding the motor end plate (neural portion of NMJ). He described PSCs as "arborisation nuclei" due to their many projections into the synapse seen under the microscope. These cells were distinguished from muscle fibre nuclei and the motor end plate, making the third component of the tripartite synaptic model.