Enhancement of extracellular protein concentrations during long-term potentiation in the rat hippocampal slice.

The possibility that the enhancement of extracellular protein concentrations during long-term potentiation is related to the maintenance of long-term potentiation was examined in area CA1 of rat hippocampal slices. First, we found that during the 3 h after induction, long-term potentiation maintenance was correlated with a persistent enhancement of extracellular protein concentrations. Second, when the protein synthesis inhibitor cycloheximide was applied 10-15 min before long-term potentiation induction, the drug blocked both the maintenance of long-term potentiation and the elevation of extracellular protein concentrations. These results suggest that the elevation of extracellular protein concentrations requires new protein synthesis. The results further indicate that the newly synthesized proteins may play a role in the maintenance of long-term potentiation.