Autoradiographic visualization of a calcium channel antagonist, [¹²⁵I]ω-conotoxin GVIA, binding site in the brains of normal and cerebellar mutant mice (pcd and weaver)

An in vitro autoradiographic technique has been used to localize [¹²⁵I]ω-conotoxin GVIA binding sites in the brains of normal and cerebellar mutant mice. In the brains of normal mice, the highest densities of binding sites were observed at glomeruli of the olfactory bulb, cerebral cortex, caudate nucleus-putamen, hippocampus, and the nucleus of the solitary tract. Moderate densities of the silver grains occured on the granular layer of the olfactory bulb, the molecular layer of the dentate gyrus, the molecular layer of the cerebellum, and the cochlear nucleus. No specific binding appeared in the white matter or the deep nucleus of the cerebellum, the corpus callosum, the internal capsule and the external plexiform layer of the olfactory bulb. Autoradiographic studies of the cerebella of Purkinje cell degeneration (pcd) mice showed that the distribution of binding sites on the molecular layer of the cerebellum are not affected by the degeneration of Purkinje cells. However, only background levels of the silver grains occured on the cerebella of agranular weaver mutant mice, suggesting that the receptor for ω-conotoxin GVIA in the cerebellum are predominantly distributed on the parellel fibers of granule cells.