Post-Synaptic Localization of CB2 Cannabinoid Receptors in the Rat Hippocampus

BRUSCO A, TAGLIAFERRO P, SAEZ T, ONAIVI E

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Wiley Liss, Inc.

Año: 2008 vol. 62 p. 944 - 949

The expression of CB2 cannabinoid receptors (CB2-Rs) in the brain and their neuronal function has now attracted research interest since we and others have demonstrated the presence of CB2-Rs in neuronal and glial cells in the brain.  In this study we show the subcellular distribution of CB2-Rs in neuronal, glial and endothelial cells in the rat hippocampus using immunohistochemical electron microscopy.  Brain sections from the hippocampus were immunolabeled for CB2-R, visualized and analyzed by electron microscopy.  We found that in neurons, CB2-R immunoreactivity is present in the cell body as well as in large and medium-sized dendrites.  In the soma, the CB2-R labeling is associated with the rough endoplasmic reticulum and Golgi apparatus demonstrating that CB2-Rs are synthesized by hippocampal neurons.  CB2-R labeling in dendrites was observed in the cytoplasm and associated with the plasma membrane near the area of synaptic contact with axon terminals indicating a postsynaptic distribution of these receptors.  In CB2-R immunoreactive glial and endothelial cells the labeling was also found to be associated with the plasma membrane.  These results provide the first ultrastructural evidence that CB2-Rs are mainly postsynaptic in the rat hippocampus.