Characteristics and localization of high-affinity kainate sites in slide-mounted sections of rat cerebellum

The characteristics and localization of high-affinity, kainic acid (KA)-sensitive glutamate sites have been investigated using a radioreceptor procedure to provide insights into specific high affinity KA receptors identified in molecular biological studies. Binding sites identified by employing [H-3]KA, in the presence of the AMPA-selective antagonist NBQX (1 mu M), and slide-mounted, coronal sections of rat cerebellum were of high-affinity (K-d 6 nM) and possessed an unique pharmacological profile. Specific binding was to a single population of sites and fully inhibited by kainoids and glutamate, but essentially insensitive to AMPA and willardiines. Autoradiography revealed that the high-affinity KA sites were localized to the granule cell layer of cerebellum. The KA site resembled both the KA receptor found on spinal motoneurones and the KA-2 type of receptor.