Interactions between arachidonic acid and metabotropic glutamate receptors in the induction of synaptic potentiation in the rat hippocampal slice

Perfusion of neither the metabotropic glutamate receptor agonist (1S,3R)-1-aminocyclopentane-1,3-dicarboxylic acid (ACPD), nor arachidonic acid caused any long-term enhancement of synaptic transmission in the CA1 region of the rat hippocampal slice. However, co-perfusion of ACPD (50 mu M) and arachidonic acid (10 mu M) for 5 min induced a rapidly evoked and long-lasting enhancement of synaptic transmission. This enhancement persisted in the presence of D(-)-2-amino-5-phosphonopentanoic acid (40 mu M) and is therefore independent of NMDA receptor activation. The potentiation was mimicked by perfusion of the phospholipase A(2) activator melittin (10 mu g/ml) for 5 or 10 min, or exogenous phospholipase A(2) (1 mu g/ml) for 5 min, immediately before ACPD application. We propose a role for arachidonic acid in the induction of synaptic potentiation, possibly as a retrograde transmitter substance.