Sigma Receptor (σR)
Sigma receptors [σRs] are a relatively novel group of receptors originally discovered in the central nervous system [CNS] of mammals in 1976. They represent a ubiquitously expressed unique binding site in the CNS and other peripheral tissues. σRs are a member of the orphan receptor class for which no endogenous ligand was known until recently – dimethyltryptamine [DMT] (Fontanilla et al. 2009). They also bind with high affinity to several classes of chemically unrelated ligands such as neurosteroids, neuroleptics, dextrobenzomorphans, and several psychostimulants such as cocaine, methamphetamine, methylenedioxymethamphetamine, and methacathinone. Consequently, it is thought that the σR may mediate the immunosuppressant, antipsychotic, and neuroprotective effects of many drugs (Niitsu et al. 2012).
Historically, the σR was identified as one of the subtypes of opiate receptors, differentiated using a chronic spinal...