Kainic acid binding to membranes of striatal neurons.

The specific binding of ³H]-kainic acid to membrane fragments of rat striatum was examined. The specific binding was found to be saturable and of high affinity. The dissociation constant was about 71 nM, while the apparent maximal number of receptor sites was 254 fmoles/mg protein. ³H]-Kainic acid binding was effectively competed by both unlabeled kainic acid and glutamate, Lesions of the striatum by stereotaxic injection of 5 nmoles of kainic acid reduced the density of ³H]-kainic acid binding sites by half, without affecting their affinity. Lesions of the cortico-striatal afferents, however, did not affect the binding of ³H]-kainic acid, although sodium-dependent glutamate uptake was reduced by 30%. It is concluded that ³H]-kainic acid binds to a population of receptors localized on neurons of the caudate-putamen.