Bi-directional plasticity and age-dependent long-term depression at mouse CA3-CA1 hippocampal synapses

Low-frequency stimulation (LFS) is used to induce long-term depression (LTD) and depotentiation at rodent CA3-CA1 hippocampal synapses. The relationship between the efficacy of LFS induction and postnatal age remains to be clearly defined in rat and had not been studied in mouse. The data presented here show that in acute mouse hippocampal slices LFS-induced LTD and depotentiation at CA3-CA1 synapses are: synapse specific; NMDA receptor-dependent; and metabotropic glutamate (mGlu) receptor type I/II independent. Furthermore LFS-induced LTD is highly age-dependent whilst long-term potentiation (LTP) and depotentiation are not. In slices from very young mice (P6-9) LFS induced a robust and stable LTD (-31.1 +/- 5.9%, n = 8, P < 0.01) of CA1 field excitatory post-synaptic potentials (fEPSPs), measured 55-60 min after conditioning. LFS also induced LTD in slices from mice aged P10-13 and P14-17 (-16.0 +/- 3.0%, n = 35, P < 0.001 and -17.9 +/- 5.5%, n = 12, P < 0.01, respectively). However, LTD was not expressed in slices from animals aged P18-21 ( -7.0 +/- 4.1%, n = 16, P > 0.05) or older.