Although termed ‘receptors’, the evidence for coupling through conventional signalling pathways is lacking. Initially described as a subtype of opioid receptors, there is only a modest pharmacological overlap and no structural convergence with the G protein-coupled receptors. A wide range of compounds, ranging from psychoactive agents to antihistamines, have been observed to bind to these sites, which appear to be intracellular.

(-)-Pentazocine also shows activity at opioid receptors.

* Key recommended reading is highlighted with an asterisk

* de Medina P, Paillasse MR, Ségala G, Khallouki F, Brillouet S, Dalenc F, Courbon F, Record M, Poirot M, Silvente-Poirot S. (2011) Importance of cholesterol and oxysterols metabolism in the pharmacology of tamoxifen and other AEBS ligands. Chem. Phys. Lipids, 164 (6): 432-7. [PMID:21641337]

* Dubrovsky B. (2006) Neurosteroids, neuroactive steroids, and symptoms of affective disorders. Pharmacol. Biochem. Behav., 84 (4): 644-55. [PMID:16962651]

* Guitart X, Codony X, Monroy X. (2004) Sigma receptors: biology and therapeutic potential. Psychopharmacology (Berl.), 174 (3): 301-19. [PMID:15197533]

* Matsumoto RR, Liu Y, Lerner M, Howard EW, Brackett DJ. (2003) Sigma receptors: potential medications development target for anti-cocaine agents. Eur. J. Pharmacol., 469 (1-3): 1-12. [PMID:12782179]

1. Berardi F, Colabufo NA, Giudice G, Perrone R, Tortorella V, Govoni S, Lucchi L. (1996) New sigma and 5-HT1A receptor ligands: omega-(tetralin-1-yl)-n-alkylamine derivatives. J. Med. Chem., 39 (1): 176-82. [PMID:8568804]

2. Lever JR, Gustafson JL, Xu R, Allmon RL, Lever SZ. (2006) Sigma1 and sigma2 receptor binding affinity and selectivity of SA4503 and fluoroethyl SA4503. Synapse, 59 (6): 350-8. [PMID:16463398]

3. Mach RH, Wu L, West T, Whirrett BR, Childers SR. (1999) The analgesic tropane analogue (+/-)-SM 21 has a high affinity for sigma2 receptors. Life Sci., 64 (10): PL131-7. [PMID:10096443]

4. Matsumoto RR, Bowen WD, Tom MA, Vo VN, Truong DD, De Costa BR. (1995) Characterization of two novel sigma receptor ligands: antidystonic effects in rats suggest sigma receptor antagonism. Eur. J. Pharmacol., 280 (3): 301-10. [PMID:8566098]

5. Okuyama S, Imagawa Y, Ogawa S, Araki H, Ajima A, Tanaka M, Muramatsu M, Nakazato A, Yamaguchi K, Yoshida M et al.. (1993) NE-100, a novel sigma receptor ligand: in vivo tests. Life Sci., 53 (18): PL285-90. [PMID:7901723]

6. Prezzavento O, Campisi A, Ronsisvalle S, Li Volti G, Marrazzo A, Bramanti V, Cannavò G, Vanella L, Cagnotto A, Mennini T et al.. (2007) Novel sigma receptor ligands: synthesis and biological profile. J. Med. Chem., 50 (5): 951-61. [PMID:17328523]

7. Su TP, Wu XZ, Cone EJ, Shukla K, Gund TM, Dodge AL, Parish DW. (1991) Sigma compounds derived from phencyclidine: identification of PRE-084, a new, selective sigma ligand. J. Pharmacol. Exp. Ther., 259 (2): 543-50. [PMID:1658302]