An electron spin resonance study of synaptosome opiate receptors. The preparation and use of a spin labeled morphine

Morphine spin labeled on the phenolic hydroxy group has been prepared using commercially available reagents and characterized by thin layer chromatography, mass spectroscopy, and electron spin resonance spectroscopy. It has been shown that morphine modified in this way retains some opiate activity, does not pass through the blood-brain barrier, and specifically binds to isolate rat brain synaptosomes. Spin labeled morphine has been shown to be an effective biophysical probe complementing radioactive tracer techniques in the study of the narcotic receptor site.