Immunocytochemical localization of the sigma(1) receptor in the adult rat central nervous system

In order to characterize the localization of the sigma(1) receptor in the a dult rat central nervous system, a polyclonal antibody was raised against a 20 amino acid peptide, corresponding to the fragment 143-162 of the cloned sigma(1) receptor protein. Throughout the rostrocaudal regions of the cent ral nervous system extending from the olfactory bulb to the spinal cord, in tense to moderate immunostaining was found to be associated with: (i) epend ymocytes bordering the entire ventricular system, and (ii) neuron-like stru ctures located within the parenchyma. Double fluorescence studies confirmed that, throughout the parenchyma, sigma, receptor-immunostaining was essent ially associated with neuronal structures immunostained for the neuronal ma rker beta III-tubulin. In all rats examined, high levels of immunostaining were always associated with neurons located within specific regions includi ng the granular layer of the olfactory bulb, various hypothalamic nuclei, t he septum, the central gray, motor nuclei of the hindbrain and the dorsal h orn of the spinal cord. In contrast, only faint immunostaining was associat ed with neurons located in the caudate-putamen and the cerebellum. Electron microscope studies indicated that sigma(1) receptor immunostaining was mos tly associated with neuronal perikarya and dendrites, where it was localize d to the limiting plasma membrane, the membrane of mitochondria and of some cisternae of the endoplasmic reticulum. At the level of synaptic contacts, intense immunostaining was associated with postsynaptic structures includi ng the postsynaptic thickening and some polymorphous vesicles, whereas the presynaptic axons were devoid of immunostaining. These data indicate that the sigma(1) receptor antibody prepared here, repr esents a promising tool for further investigating the role of ol receptors. (C) 2000 IBRO. Published by Elsevier Science Ltd.