Ultrastructure of the neuro-insular complexes in the pancreas of sand rats (Psammomys obesus).

The ultrastructure of the nervous elements in Langerhans islets of Psammomys obesus has been studied. A great variety of neural structures present in the islets has been described: neuroganglion-, enterochromaffin- and satellite Schwann cells (neuro-insular complexes type I) and cholinergic, adrenergic and peptidergic nerve fibers (neuro-insular complexes type II) in direct contact with the endocrine cells. In the pericapillary space typical neuro-vasal endings of neurosecretory type have been described. The islets of Langerhans and some of the endocrine cells have a total or partial glial sheath. These findings support the thesis of the paraneuronal nature of the endocrine cells of the Langerhans islets.