SOLUBILIZATION AND CHARACTERIZATION OF BINDING-SITES FOR [H-3] NE-100, A NOVEL AND POTENT SIGMA1 LIGAND, FROM GUINEA-PIG BRAIN

The binding sites for [H-3]NE-100, a newly defined sigmal ligand, was solubilized from guinea pig brain, using zwitterionic detergent -chola midopropyl)dimethylamino]-1-propanesulfonate (CHAPS), and the properti es of the solubilized binding sites were compared to those for [H-3]()-pentazocine, a selective sigmal ligand. The pharmacological selectiv ity of solubilized sites for both [H-3]NE-100 and [H-3](+)-pentazocine was identical to that obtained from membrane preparations. Stereosele ctivity of benzomorphan such as pentazocine and SKF10,047 was preserve d in displacing [H-3]NE-100 binding in solubilized preparations as obs erved in membrane preparations. The inhibitory potencies of several si gma ligands on [H-3]NE-100 binding were similar to those on [H-3](+)-p entazocine binding, indicating that the pharmacological characteristic s of the binding sites for [H-3]NE-100 are retained after solubilizati on. Phenytoin augmented the binding of [H-3](+)-3-(3-hydroxyphenyl)-N- (1-propyl) piperidine hydrochloride (3-PPP) to solubilized sigma bindi ng sites while it had no effect on the binding of [H-3]NE-100. Further more, the inhibitory effect of putative sigma receptor agonists such a s (+)-3-PPP and dextromethorphan were enhanced by phenytoin; the effec ts of haloperidol, a putative sigma receptor antagonist, were unaltere d. Molecular weight of [H-3]NE-100 binding protein was estimated to be 440KDa by Sepharose CL-6B gel filtration chromatography, and the valu e was identical to that of [H-3](+)-pentazocine binding protein, a put ative sigmal binding protein. These findings indicate that [H-3]NE-100 binding sites are putative sigmal binding sites, and that NE-100 may act as an antagonist at sigmal binding sites.