Further characterization of [ 3H]ifenprodil binding to σ receptors in rat brain

Abstract

This study was undertaken to examine further the pharmacology of [ 3H]ifenprodil binding in rat brain at 37°C. [ 3H]Ifenprodil bound specifically to membranes ( K d = 5.09 ± 0.30 nM; B max = 2.36 ± 0.19 pmol/mg protein). [ 3H]Ifenprodil binding was potently inhibited by σ ligands and inhibitors of cytochrome P-450. The levorotatory enantiomers of pentazocine and SKF 10,047 were more potent inhibitors than corresponding dextrorotatory enantiomers. Furthermore, the pharmacological profile of [ 3H]ifenprodil binding was highly correlated with that of σ 2 sites, not σ 1 sites. The results suggest that [ 3H]ifenprodil labels σ 2 sites in rat brain at 37°C, and that [ 3H]ifenprodil would be useful for studying σ receptor subtypes