Brain metabolism and the acquisition of new behaviors. III. Evidence for secretion of two proteins into the brain extracellular fluid after training.

Immunochemical and double labeling experiments were used to demonstrate that at least two out of three brain cytoplasmic proteins, whose metabolism is markedly influenced by behavior, are products which are secreted into the extracellular fluid (ECF) of goldfish brain. Even after 1 h of labeling, the extracts of goldfish brains with 0.32 M sucrose were found to contain highly labeled proteins. Electrophoretic analyses of the proteins, on SDS polyacrylamide gels, indicated that an increased incorporation of [3H]valine occurs for trained animals as compared to untrained controls ([14C]valine) at specific protein bands migrating at 32,000 and 26,000 daltons. The proteins in the ECF gave identical precipitin bands to goldfish brain proteins whose metabolism was responsive to the acquisition of new patterns of behavior and to proteins in CSF. These results are consistant with the hypothesis that the cells which contain the proteins and whose location in the ependymal zone was determined by immunohistochemistry can secrete the products into ECF. It is therefore quite possible that the functional sites of the proteins are away from the locus of their synthesis.