LOCALIZATION OF DOPAMINE D-3 RECEPTOR IN THE RAT CEREBELLAR CORTEX - A LIGHT-MICROSCOPE AUTORADIOGRAPHIC STUDY

The pharmacological properties and the anatomical localisation of dopa mine Dg receptor were assessed in the rat cerebellar cortex using radi oligand binding techniques associated with light microscope autoradiog raphy and 7-[H-3]hydroxy-N,N-di-n-propyl-2-aminotetralin (7-[H-3]OH-DP AT) as a ligand. 7-[H-3]OH-DPAT was specifically bound to sections of rat cerebellar cortex with a dissociation constant (K-d) of 0.5 nM and a maximum density of binding sites (B-max) of 97 +/- 4 fmol/mg tissue . The rank order of potency of competitors of 7-[H-3]OH-DPAT binding a nd the observation that guanosine triphosphate did not affect radiolig and binding suggest the labelling of a dopamine Dg receptor. 7-[H-3]OH -DPAT binding sites are located mainly in the molecular layer and in l esser amounts in the Purkinje neuron layer, primarily within the cell body of Purkinje neurons. No specific accumulation of silver grains wa s observed in the granule neuron layer or in the white matter of the c erebellar cortex. The localisation of a putative dopamine Dg receptor within Purkinje neurons suggests that this site may have functional re levance in the cerebellar cortex.