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Brainstorms: The Sigma Enigma: Can Sigma Receptors Provide a Novel Target for Disorders of Mood and Cognition?

J Clin Psychiatry 2008;69(11):1673-1674

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Sigma receptors are provocative, mysterious, and controversial targets of many psychotropic drugs and are only now beginning to be understood. Sigma receptors are not a type of opiate receptor nor a type of receptor on the NMDA (N-methyl-D-aspartate) glutamate receptor complex, but they are now known to be a unique set of proteins with at least 2 subtypes of receptors: σ1 and σ2.​

Sigma receptors are located in many tissues where they represent sites in the endoplasmic reticulum (ER), not in cell membranes.1–3