Long-term potentiation in the dentate gyrus of the anaesthetized rat is accompanied by an increase in protein efflux into push-pull cannula perfusates

Changes in protein content of push-pull cannula perfusates from the dentate gyrus of anaesthetized rats were analyzed before and after the induction of long-term potentiation (LTP). LTP, induced by either high-frequency stimulation of the perforant path or raising the extracellular calcium concentration, was associated with increases in the protein content of the perfusates. Tetanically induced LTP was accompanied with a large but delayed increase (apparent in the second hour after the stimulation) in protein efflux. In contrast, when LTP was induced by the elevation of extracellular calcium concentration, a smaller but more immediate increase in protein efflux was observed. When 5-D-aminophosphonovalerate was used to block the induction of LTP, no increase was observed in either case. These results indicate that LTP in the dentate gyrus is accompanied by an increase in the efflux of proteins into push-pull cannula perfusates. The possible origins of these proteins and their role in LTP are discussed.