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Nat Neurosci. 2010 May;13(5):592-600. doi: 10.1038/nn.2517. Epub 2010 Mar 28.

Reduction in endocannabinoid tone is a homeostatic mechanism for specific inhibitory synapses.

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1
Departments of Physiology, University of Maryland School of Medicine, Baltimore, Maryland, USA.

Abstract

When chronic alterations in neuronal activity occur, network gain is maintained by global homeostatic scaling of synaptic strength, but the stability of microcircuits can be controlled by unique adaptations that differ from the global changes. It is not understood how specificity of synaptic tuning is achieved. We found that, although a large population of inhibitory synapses was homeostatically scaled down after chronic inactivity, decreased endocannabinoid tone specifically strengthened a subset of GABAergic synapses that express cannabinoid receptors. In rat hippocampal slice cultures, a 3-5-d blockade of neuronal firing facilitated uptake and degradation of anandamide. The consequent reduction in basal stimulation of cannabinoid receptors augmented GABA release probability, fostering rapid depression of synaptic inhibition and on-demand disinhibition. This regulatory mechanism, mediated by activity-dependent changes in tonic endocannabinoid level, permits selective local tuning of inhibitory synapses in hippocampal networks.

PMID:
20348918
PMCID:
PMC2860695
DOI:
10.1038/nn.2517
[Indexed for MEDLINE]
Free PMC Article

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