CHARACTERIZATION AND DISTRIBUTION OF MU-OPIOID RECEPTORS IN RABBIT CEREBELLUM

The binding characteristics and distributions of [H-3]ohmefentanyl ([H -3]OMF), [H-3]etorphine, yl-N-[7-(I-pyrrolidinyl)-1-oxa-spiro(4,5)dec- 8-yl] benzeneacetamide [H-3]U-69593), and [H-3] (D-penicillamine2, D-p enicillamine5) enkephalin ([H-3]DPDPE) in rabbit cerebellum were studi ed. In saturation experiment, [H-3]OMF bound to a single population of sites with K(d) = 2.2 +/- 1.3 nmol . L-1 and B(max) = 69 +/- 13 fmol/ mg protein. The results of [H-3]etorphine (K(d) = 1.0 +/- 0. 4 nmol . L-1 and B(max) = 16 +/- 6 fmol/mg protein) were similar to those of [H -3]OMF. There were no specific bindings of [H-3]U-69593 and [H-3]DPDPE in rabbit cerebellar membranes. In autoradiographic study, the gray s cales of specific binding for [H-3] OMF , [H-3] etorphine , [H-3]U-695 93, and [H-3]DPDPE were 20.2 +/- 4.6, 8.5 +/- 2. 7, 2. 0 +/- 0. 7, and 3. 2 +/- 4. 3, respectively. The gray matter of rabbit cerebellum was intensely labeled by [H-3]OMF and [H-3]etorphine, but not by [H-3]U-6 9593 or [H-3]DPDPE. These results suggested that the rabbit cerebellum contained mu opioid receptors.