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Sci. STKE, 28 September 2004
Vol. 2004, Issue 252, p. tw348
[DOI: 10.1126/stke.2522004tw348]

EDITORS' CHOICE

SYNAPTIC PLASTICITY Endocannabinoids Lower the LTP Threshold

Endocannabinoids have been implicated in various forms of synaptic depression (see Related Resources and Fitzjohn and Collingridge). Chevaleyre and Castillo demonstrate that endocannabinoid-mediated long-term depression of inhibitory synapses (I-LTD) in the hippocampus lowers the threshold for the induction of long-term potentiation (LTP) of nearby excitatory synapses. Only theta-burst stimuli (TBS) that were close (10 μm) to the site of the induced inhibitory postsynaptic potentials (IPSPs) produced I-LTD. (TBS is a well-established repetitive stimulation protocol that can produce long-term synaptic changes.) Using a stimulation frequency that produced I-LTD, but not LTP in the excitatory Schaffer collateral to CA1 synapses, the authors triggered I-LTD and then investigated the magnitude of the LTP produced in response to subsequent stimuli. LTP magnitude was larger following priming by I-LTD, and this effect required GABAA ion channels and the CB1 endocannabinoid receptor. The authors suggest that repetitive stimulation produces LTP directly in a restricted region and I-LTD in a wider region, because lower stimulation frequencies are required, and this I-LTD facilitates the induction of LTP in synapses adjacent to those directly receiving the repetitive stimuli.

S. M. Fitzjohn, G. L. Collingridge, Endocannabinoids: Losing inhibition to increase learning capacity? Neuron 43, 762-764 (2004). [Online Journal]

V. Chevaleyre, P. E. Castillo, Endocannabinoid-mediated metaplasticity in the hippocampus. Neuron 43, 871-881 (2004). [Online Journal]

Citation: Endocannabinoids Lower the LTP Threshold. Sci. STKE 2004, tw348 (2004).



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