The distribution of [³H]kainate binding sites in primate hippocampus is similar to the distribution of both Ca²⁺-sensitive and Ca²⁺-insensitive [³H]kainate binding sites in rat hippocampus

The distribution of [³H]kainate binding sites was determined by quantitative autoradiography in three vertebrate species: rat, monkey, and human. These animals displayed a similar pattern of binding site density in the hippocampus. Highest levels were found within the stratum lucidum and moderate levels in the inner portion of the dentate gyrus molecular layer. Although the distribution is similar, there is a lower density of binding sites in the stratum lucidum of primates than in rodents. Experiments using rat brain synaptic plasma membrane fractions indicated that inclusion of Ca²⁺ ions results in a selective reduction in binding at the high affinity sites. The Ca²⁺-inhibited and Ca²⁺-insensitive binding sites in the rat hippocampus exhibited a similar distribution. Together, these results suggest that in a variety of mammalian species kainate receptors exhibit similar regional distributions, and that the high anf loe affinity kainate binding sites also exhibit similar regional distributions.