Immunohistochemical localization of the sigma₁ receptor in Schwann cells of rat sciatic nerve

The sigma-1 (σ1) receptors can bind different psychotropic drugs and have been implicated in schizophrenia, depression and dementia. The cloning of the σ1-receptor has allowed to obtain specific antibodies and, in a recent immunohistochemical study, we demonstrated that, in addition to neurons, the σ1-receptor is located in oligodendrocytes [Brain Res. 961 (2003) 92.]. In the present study using in vivo and in vitro techniques, we demonstrate the localization of the σ1-receptor in Schwann cells. Double immunofluorescence studies showed that σ1-receptor co-localized with S100 protein, a specific marker of Schwann cells, in both rat sciatic nerve Schwann cells and Schwann cells in cultures. The σ1-receptor immunoreactivity was seen in the cytoplasm and paranodal region formed by these cells, but not in myelin itself. The presence of σ1-receptor in oligodendrocytes and Schwann cells is discussed on the basis on recent findings involving this receptor in lipid metabolism, compartmentalization and transport to the plasma membrane, thus suggesting a role for σ1-receptor signaling in myelination. © 2004 Elsevier B.V. All rights reserved.