The presence and possible significance of agranular reticulum in paranodal oligodendrocyte cytoplasm and in periglomerular astrocyte processes.

Paranodal glial loops (lateral belt cytoplasm) of myelinated CNS and PNS fibres contain tubules of agranular reticulum, as well as microtubules, wound spirally around the axon. Similar agranular elements run circumferentially in the expanded rims of sheet-like astrocytic processes encapsulating thalamic synaptic glomeruli. A role for agranular reticulum in these sites in control of the ionic composition of adjacent cellular and extracellular compartments is suggested.