[Long-term depression of excitatory synapses in the cortex and hippocampus].
The efficacy of excitatory synapses terminating on cortical and hippocampal pyramidal cells may be persistently depressed as well as potentiated. Homo-synaptic long-term depression (LTD) seems to be triggered by an entry of calcium into a post-synaptic cell less than that needed to initiate long-term potentiation (LTP). Theoretical work predicted, and experimental studies confirmed, that moderate elevations of calcium initiate LTD via a cascade of biochemical interactions involving calcium-dependent phosphatases. Genetically modified animals confirmed the prediction of a sliding threshold that defines the limit between LTD and LTP. While mechanisms for the initiation of LTD are quite well established, it remains unclear whether pre- or post-synaptic mechanisms, or both, are involved in its maintenance. A role for LTD in processes of learning and forgetting in the adult animal remains to be firmly established. It seems probable, however, that a persistent reduction in synaptic weight is a basic process used in the establishment and refinement of neuronal circuits during development.
Laboratoire de neurobiologie cellulaire, Inserm U261, Institut Pasteur, Paris, France.
I
I
Cohen
P
P
Parra
R
R
Miles
D000818:Animals; D002118:Calcium / Q000502:physiology; D002540:Cerebral Cortex / Q000502:physiology*; D006624:Hippocampus / Q000502:physiology*; D009473:Neuronal Plasticity / Q000502:physiology*; D016194:Receptors, N-Methyl-D-Aspartate / Q000502:physiology; D009435:Synaptic Transmission / Q000502:physiology*
D016194:Receptors, N-Methyl-D-Aspartate; D002118:Calcium
Dépression à long-terme des synapses excitatrices dans le cortex et l'hippocampe.