Block of HFS-induced LTP in the dentate gyrus by 1S,3S-ACPD: further evidence against LTP as a model for learning.

We have previously shown that block of high-frequency stimulation (HFS) induced long-term potentiation (LTP) of synaptic transmission in area CA1 by (1S,3S)-1-aminocyclopentane-1,3-dicarboxylic acid (1S,3S-ACPD; 5 microliters of a 20 mM solution), an agonist at group II metabotropic glutamate receptors, did not prevent animals from learning a spatial task. Here we show that the same dose of 1S,3S-ACPD also blocked the induction of HFS-induced LTP of the slope of the excitatory postsynaptic potential and of the amplitude of the population spike in the dentate gyrus. We conclude that HFS-induced LTP in the dentate gyrus is not a good model for memory formation.