Editorial

Abstract

The concept of sigma receptors or sigma binding sites emerged in the late seventies out of the field of opiate receptor research, when the dysphoric effects of several new opiate drugs could not sufficiently be explained by interaction with one of the known opiate receptors. Originally proposed as an additional subtype of opiate receptors it was soon recognized that the newly designed sigma site was distinct from the different subtypes of opiate receptors (typical G-protein coupled membrane receptors) but seemed to represent first candidates of a new class of drug binding sites with rather atypical localization (largely intracellularly), of unknown transduction mechanism and with rather obscure cellular functions. Similarly, their pharmacological relevance remained in dispute.