Spatial exploration induces a persistent reversal of long-term potentiation in rat hippocampus.
Experience-dependent long-lasting increases in excitatory synaptic transmission in the hippocampus are believed to underlie certain types of memory. Whereas stimulation of hippocampal pathways in freely moving rats can readily elicit a long-term potentiation (LTP) of transmission that may last for weeks, previous studies have failed to detect persistent increases in synaptic efficacy after hippocampus-mediated learning. As changes in synaptic efficacy are contingent on the history of plasticity at the synapses, we have examined the effect of experience-dependent hippocampal activation on transmission after the induction of LTP. We show that exploration of a new, non-stressful environment rapidly induces a complete and persistent reversal of the expression of high-frequency stimulation-induced early-phase LTP in the CA1 area of the hippocampus, without affecting baseline transmission in a control pathway. LTP expression is not affected by exploration of familiar environments. We found that spatial exploration affected LTP within a defined time window because neither the induction of LTP nor the maintenance of long-established LTP was blocked. The discovery of a novelty-induced reversal of LTP expression provides strong evidence that extensive long-lasting decreases in synaptic efficacy may act in tandem with enhancements at selected synapses to allow the detection and storage of new information by the hippocampus.
Xu
L
L
Department of Pharmacology and Therapeutics, Trinity College, Dublin, Ireland.
Anwyl
R
R
Rowan
M J
MJ
D000818:Animals; D019706:Excitatory Postsynaptic Potentials; D005106:Exploratory Behavior / Q000502:physiology*; D006624:Hippocampus / Q000502:physiology*; D007858:Learning / Q000502:physiology; D017774:Long-Term Potentiation / Q000502:physiology*; D008297:Male; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors