Fish brains were homogenized in an all-glass Potter-Elvehjem-type tissue grinder in 40% sucrose solution. The homogenate concentration was 10 brains/ml for both the bluegill and channel catfish. The brei was centrifuged at 34,700 g for 30 min at 5 C, and 30 J.lliters of the supernatant were used per column for electrophoresis.