Original Paper	Pharmacopsychiatry 2004; 37: 183-188 DOI: 10.1055/s-2004-832676
© Georg Thieme Verlag KG Stuttgart · New York
Behavioral Pharmacology of σ-Ligands
G. Skuza1, K. Wedzony1
1 Institute of Pharmacology, Polish Academy of Sciences, 31-343 Krakow PL

Sigma (σ) receptors, first defined as a subclass of opioid receptors, later confounded with the high affinity phencyclidine (PCP) binding sites, now are regarded as unique binding sites, distinct from opiate and PCP receptors, and related to higher brain function. The investigation of functional significance of σ receptors in the brain has been hampered for many years by relative lack of specific tool drugs and by the unavailability of their coherent classification into postulated agonists and antagonists. However, a potential involvement of σ receptors in psychotic disorders was first suggested soon after their discovery. The σ receptors are classified into two subtypes, σ₁ and σ₂ receptors, of which the first was recently cloned from rodent and human tissues while the second has not yet been fully characterized. Although the precise mechanism of the functional response of these receptors is still uncertain, it is accepted that σ receptors can modulate a number of central neurotransmitter systems, including noradrenergic, glutamatergic and dopaminergic ones. The σ receptors have been postulated to be involved in numerous pharmacological and physiological functions, including motor disorders, psychotic disorders, neuroprotective mechanisms. In the last years, a number of compounds with a high affinity and selectivity for σ binding sites have been discovered and investigated for their therapeutic potential. In this review, we try to summarize the behavioral effects of σ receptor ligands that have been described, and their activity in animal models related to some brain disorders, especially schizophrenia and affective disorders.