STATUS EPILEPTICUS REORGANIZES CANNABINOID RECEPTORS

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The central nervous system cannabinoid receptor (CB1) is one of the most abundant G-Protein coupled receptors in brain and mediates many of the effects of cannabinoid substances on neuronal function. Our laboratory has demonstrated that one hour of prolonged seizures (status epilepticus, SE) in the pilocarpine model of SE produces a long-term reorganization in the expression of the CB1 receptor ahd that these changes in CB1 expression persist for essentially the life of the animal. SE is a major neurological emergency that has a high mortality and morbidity, including acquired epilepsy (AE) and memory deficits. Our preliminary results suggest that the SE induced persistent changes in expression and function of the CB1 receptor are reorganized to be decreased on inhibitory and increased on excitatory nerve terminals, indicating that this long-term plasticity change may represent a significant modulator of neuronal function. This research effort will test the Central Hypothesis that SE (acute event) causes long lasting reorganization in the expression of the CB1 that results in persistent changes in the overall function of the endocannabinoid system, causing a greater inhibition of glutamate release and a smaller inhibition of GABA release in epileptic compared to control brain and ultimately in changes in the behavior of the animal, as manifested by memory deficits. To test this hypothesis we will conduct the following specific aims: Aim 1. Evaluate whether SE alone or with the development of AE causes persistent rearrangements in the immunoreactivity and expression of the CB1 receptor in brain and evaluate the time course of these changes; Aim 2. Determine if the SE induced changes in CB1 receptor expression are associated with corresponding changes in CB1 function as determined by G-protein activation, receptor binding and regulation of neurotransmiter release; Aim 3. Determine the association of SE induced CB1 receptor reorganization on excitatory and inhibitory nerve terminals; Aim 4. Determine the effects of long-term plasticity changes in CB1 expression and function on the long-term memory effects observed after SE. The goal of this research is to determine if changes in the expression of the CB1 system following SE contribute to altered neuronal excitability and memory deficits produced by SE. These studies may lead to the development of novel therapeutic interventions to reverse the effects of SE on AE and memory loss by pharmacologically regulating the endogenous CB1system.