Saturday, May 08, 2010

TRPV1 Expression and Temporal Lobe Epilepsy

Dr Bret. Smith and his lab at Tulane have demontrated a link between Temporal Lobe Epilepsy (TLE) and VR1 N-Terminus (TRPV1) expression.

In this excellent study they showed an increase in expression in TLE mice vs controls.

Muthu D. Bhaskaran and Bret N. Smith. Effects of TRPV1 activation on synaptic excitation in the dentate gyrus of a mouse model of temporal lobe epilepsy. doi:10.1016/j.expneurol.2010.01.021
...with polyclonal VR1 N-terminus (1:2500) (Neuromics, Edina)..

Abstract: Temporal lobe epilepsy (TLE) is a condition characterized by an imbalance between excitation and inhibition in the temporal lobe. Hallmarks of this change are axon sprouting and accompanying synaptic reorganization in the temporal lobe. Synthetic and endogenous cannabinoids have variable therapeutic potential in treating intractable temporal lobe epilepsy, in part because cannabinoid ligands can bind multiple receptor types. This study utilized in vitro electrophysiological methods to examine the effect of transient receptor potential vanilloid type 1 (TRPV1) activation in dentate gyrus granule cells in a murine model of TLE. Capsaicin, a selective TRPV1 agonist had no measurable effect on overall synaptic input to granule cells in control animals, but significantly enhanced spontaneous and miniature EPSC frequency in mice with TLE. Exogenous application of anandamide, an endogenous cannabinoid that acts at both TRPV1 and cannabinoid type 1 receptors (CB1R), also enhanced glutamate release in the presence of a CB1R antagonist. Anandamide reduced the EPSC frequency when TRPV1 were blocked with capsazepine. Western blot analysis of TRPV1 receptor indicated protein expression was significantly greater in the dentate gyrus of mice with TLE compared with control mice. This study indicates that a prominent cannabinoid agonist can increase excitatory circuit activity in the synaptically reorganized dentate gyrus of mice with TLE by activating TRPV1 receptors, and suggests caution in designing anticonvulsant therapy based on modulating the endocannabinoid system.

Images: Western blot detection of TRPV1 receptor expression in the dentate gyrus. A. Diagram of dentate gyrus showing the microdissected area (box). B. Western blot showing TRPV1 receptor expression in two untreated mice and in two pilocarpine-treated mice that survived SE. Actin was used as the loading control which did not change significantly. C. Graph showing a significant (p less than 0.05; n=4) TRPV1 expression in epileptic mice.

Related Reagents:

TRPV (Vanilloid); TRPM; TRPA and TRPCs

Neurotransmission Research Antibodies
-GPCRs, Ligand Gated Ion Channels, Biogenic Amines and more

Primary Neurons and Astrocytes
- Primary human, rat and mouse neurons and astrocytes by Category.

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