Pharmacology of calcium-induced long-term potentiation in rat hippocampal slices

A transient increase (10 min) in extracellular calcium concentration (4 mM) causes a long-lasting (greater than 2 hr) enhancement of population spike responses evoked by radiatum fibers to CA1 pyramidal neurons in rat hippocampal slices. This phenomenon is similar to tetanic long-term potentiation (LTP), and is also related to memory processes. The influence of various drugs was investigated on calcium-induced LTP. The NMDA antagonist 2 amino-5-phosphonopentanoic acid (AP5; 100 microM) was able to prevent the calcium-induced LTP, while atropine sulphate (10 microM), propranolol hydrochloride (10 microM) and verapamil hydrochloride (100 microM) were ineffective. The results suggest an involvement of the NMDA receptor in the development of calcium-induced LTP.