Opioid binding sites of the kappa-type in guinea-pig cerebellum.
(-)-[3H]Bremazocine interacts almost equally well with the mu-, delta- and kappa-types of opioid binding sites. In homogenates of guinea-pig cerebellum, it was bound with high affinity (KD = 0.046 nM) and the maximum binding capacity was 7.04 pmol/g wet wt of tissue. When the mu- and delta-binding of (-)-[3H]bremazocine was prevented with unlabelled ligands, a KD of 0.034 nM and a capacity of 5.94 pmol/g tissue was found for the kappa-binding site, which therefore comprised 84% of the opioid binding sites in the cerebellum. Autoradiographic analysis showed that the binding of (-)-[3H]bremazocine was relatively low in lobules IX and X and that it was predominantly located in the molecular and to a lesser extent in the granular layers. The addition of unlabelled mu- and delta-ligands did not alter the distribution. Thus, the guinea-pig cerebellum contains opioid binding sites of which almost all are of the kappa-type and is therefore an ideal tissue for the isolation of kappa-receptors and for the investigation of their biochemical and pharmacological properties.
D000818:Animals; D001345:Autoradiography; D001575:Benzomorphans / Q000031:analogs & derivatives / Q000378:metabolism; D002531:Cerebellum / Q000378:metabolism*; D006168:Guinea Pigs; D008297:Male; D051379:Mice; D011817:Rabbits; D051381:Rats; D011957:Receptors, Opioid / Q000378:metabolism*; D017473:Receptors, Opioid, kappa; D013045:Species Specificity
D001575:Benzomorphans; D011957:Receptors, Opioid; D017473:Receptors, Opioid, kappa; C027248:bremazocine