Immunofluorescent evidence for a specific binding site for phenytoin in the cerebellum.

The regional distribution of phenytoin in the brains of experimental animals was studied using the indirect fluorescent antibody technique. Using antibodies directed against phenytoin, we observed a specific pattern of staining the Purkinje and granule cell layers of the cerebellum. An identical pattern of staining was seen in phenytoin-treated and untreated animals. Several control procedures and studies indicated that the observed pattern was not caused by nonspecific staining or autofluorescence. The distinctive staining pattern obtained using this technique can be attributed to the high molecular specificity of antigen-antibody reactions and a discrete binding site for phenytoin in the vicinity of cerebellar Purkinje and granule cells.