Potassium chloride pulse enhances mitogen-activated protein kinase activity in rat hippocampal slices.

Mitogen-activated protein (MAP) kinases have been implicated in multiple responses to extracellular stimuli. In this study we show that MAP kinase activity is enhanced after a KCl pulse. This activation correlates with an increased tyrosine phosphorylation of a 42-kDa protein as determined by antiphosphotyrosine immunoblot. The same band is found in an anti-MAP kinase immunoblot. Activity is enhanced within 1 min, reaches a maximum at 2 min, and returns to basal level after 10 min. A second peak of activity is observed between 12 and 30 min. The activation is completely blocked by 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), showing the involvement of the AMPA type of glutamate receptor. Partial inhibition of MAP kinase activation by 2-amino-5-phosphonovalerate (APV) also shows the involvement of the NMDA receptor. Because the KCl pulse used induces long-term potentiation (LTP) in rat hippocampal slice, we conclude that MAP kinase may be involved in neuronal transduction events leading to LTP.