Functional and Binding Properties of σ Receptors in Rat Cerebellum

Document Type

Journal Article

Publication Date

1-1-1995

Journal

Journal of Neurochemistry

Volume

65

Issue

6

DOI

10.1046/j.1471-4159.1995.65062509.x

Keywords

(+)‐Pentazocine; BD737; Cerebellum; DuP 734; NMDA receptor; σ receptor

Abstract

Abstract: Autoradiographic studies have shown that σ receptors are enriched in the locus coeruleus, the origin of noradrenergic projections to the cerebellum, as well as in the Purkinje, molecular, and granular layers and the interpositus cerebellar nucleus of the cerebellum itself. In contrast, the cerebellum is relatively poor in phencyclidine (PCP) binding sites, which have been historically confused with σ sites. The high ratio of σ to PCP receptors in cerebellum is advantageous for discriminating σ‐mediated physiological effects. σ agonists and antagonists have been shown to regulate N‐methyl‐d‐aspartate (NMDA)‐stimulated norepinephrine release in hippocampus, which is innervated by locus coeruleus projections. We now report that σ drugs also regulate norepinephrine release from cerebellum. In contrast to findings in the hippocampus, where regulation is via σ1 and σ2 receptors, σ‐mediated regulation in cerebellum seems to be primarily via σ1 receptors. In radioligand binding studies, we find that σ receptors primarily of the σ1 type are present in the cerebellum. We further report that binding to σ receptors in cerebellum is not affected by the addition of NMDA or glycine or by the presence of NMDA antagonists, suggesting that σ receptors are not located within the NMDA‐operated cation channel in this brain region. Copyright © 1995, Wiley Blackwell. All rights reserved

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