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

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Sigma receptors are provocative,mysterious, and controversialtargets of many psychotropic drugs andare only now beginning to be understood.Sigma receptors are not a type ofopiate receptor nor a type of receptoron the NMDA (N-methyl-D-aspartate)glutamate receptor complex, but theyare now known to be a unique set ofproteins with at least 2 subtypes of receptors:σ1 and σ2.’ ‹

Sigma receptors are located in manytissues where they represent sites inthe endoplasmic reticulum (ER), not incell membranes.^1-3‘ ‹