[(3)H]GABA binding in the cerebellum of the reeler murine mutant

In the cerebellum of the reeler mutant mouse, characterized morphologically by depletion of the granule cell population and abnormal synapse formation, increased GABA concentration and alterations in [(3)H]GABA binding have been observed. This study shows decreased affinity of the Na(+)-independent, high affinity GABA binding component of synaptosomal membranes and an increased affinity of the Na(+)-dependent, high affinity GABA binding component in reeler cerebellar homogenate and synaptic membranes. In contrast to the changes in affinity, the number of both Na(+)-dependent and Na(+)-independent binding sites was not significantly altered. The decreased affinity of the Na(+)-independent GABA binding and the increased affinity of the Na(+)-dependent binding, evidenced only in cerebellar tissue, were interpreted to indicate, respectively, hypo- and hypersensitivity of the postsynaptic and presynaptic elements of cerebellar GABAergic synapses, induced by the depressed excitatory granule cell input and/or the increased mossy fiber contact with the ectopic Purkinje cells.