Sigma receptors and sigma ligands: background to a pharmacological enigma.

Although it is now well established that the sigma receptors are distinct from neurotransmitter, neuropeptide and steroid receptors, their precise physiological role, and possible involvement in the pathology of neurological and psychiatric disorders, remains an enigma. The purpose of this short review is to provide a basis upon which to explain the pharmacological properties of such a diverse group of drugs as the antidepressants, antipsychotics and neuroprotective agents. However, a greater understanding of the importance of the sigma receptors will depend on the development of more potent and selective sigma agonists and antagonists if the therapeutic potential of the sigma receptors is to be fully realised.