Enhancement of CB1 receptor immunoreactivity in pilocarpine-induced epilepsy in mice
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1
Institute of Experimental Medicine, Hungarian Academy of Science, Hungary
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2
Department of Anatomy, Hokkaido University School of Medicine, Japan
The endocannabinoid system plays a central role in retrograde synaptic communication. Alterations affecting the endocannabinoid system were observed in epilepsy both in animal models and in humans. Using the pilocarpine model of epilepsy we examined the expression pattern of the Type 1 cannabinoid receptor (CB1) in the hippocampi of CD1 mice at a survival time of 2-3 months. Based on the behavioural signs of the acute seizures, animals were classified as “weakly” or “strongly” epileptic using the modified Racine scale. In the weak group there were only a few mild seizures, whereas in the strong group the seizures were frequent with intense motor symptoms. In the weak group none of the hippocampi were sclerotic, however in the strong group the hippocampi of mice showed sclerosis in most cases. In control samples the most intense staining of CB1-positive fibers was found in the molecular layer of the dentate gyrus (DG), in str. pyramidale of the cornu Ammonis (CA), and in the subiculum. In contrast, faint labeling was observed in the strata radiatum and granulosum. In non-sclerotic epileptic cases, CB1-immunolabelling surrounding the CA1 pyramidal cell bodies has slightly increased. In the sclerotic samples the general CB1-immunostaining was much stronger throughout the hippocampus. The most striking difference was found in the str. moleculare and granulosum of the DG, in the str. pyramidale and radiatum of the CA and in the subiculum. It is well known that CB1 receptors are expressed by glutamatergic and GABAergic terminals. Electron microscopic examination proved that our antibody labeled the CB1 receptors on terminals giving symmetric synapses. Therefore the changes of the endocannabinoid system revealed in this study are associated with the GABAergic inhibitory system and depend on the severity of the hippocampal sclerosis. The enhancement of the CB1-staining may reflect sprouting of the GABAergic interneuronal fibers.
Support: Szentágothai K. C. RET 05/2004.
Conference:
12th Meeting of the Hungarian Neuroscience Society, Budapest, Hungary, 22 Jan - 24 Jan, 2009.
Presentation Type:
Poster Presentation
Topic:
Pathophysiology and neurology - degenerative disorders
Citation:
Toth
K,
Karlocai
R,
Watanabe
M,
Freund
TF and
Magloczky
Z
(2009). Enhancement of CB1 receptor immunoreactivity in pilocarpine-induced epilepsy in mice.
Front. Syst. Neurosci.
Conference Abstract:
12th Meeting of the Hungarian Neuroscience Society.
doi: 10.3389/conf.neuro.01.2009.04.178
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Received:
05 Mar 2009;
Published Online:
05 Mar 2009.
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Correspondence:
Kinga Toth, Institute of Experimental Medicine, Hungarian Academy of Science, Budapest, Hungary, tothk@koki.hu