Cannabinoid modulation of epileptiform activity in mice

描述（由申请人提供）：癫痫研究的主要目标是确定和开发癫痫发作控制的新治疗策略，这些策略可能对癫痫大脑中突触重组电路的调节具有相对选择性。这项探索性/发展性（R21）研究计划的目的是确定外源性和内源性大麻素对匹罗卡品诱发的颞叶癫痫（TLE）小鼠齿状回神经元的影响，其特征是慢性自发发作，苔藓纤维发芽，神经元兴奋性和同步性增加。使用大麻素治疗癫痫已经被提出，但案例研究分析的结果却喜忧参半。本提案的目标是确定大麻素如何调节小鼠TLE模型中齿状回的活性，以了解该物质对经历突触重组的系统的影响（相对于对正常神经回路的影响）。大多数已知的大麻素中枢效应是由大麻素1型受体（CB1R）介导的，通常位于突触前末端。在海马体中，大麻素抑制突触输入-特别是反馈抑制-主要神经元，包括齿状回颗粒细胞。虽然大麻素似乎可以抑制某些类型的癫痫发作，但在正常大脑中，细胞“去抑制”特性似乎是前惊厥。最近的分析表明，大麻素可能会抑制癫痫患者大脑中的癫痫活动。然而，尚未对TLE动物模型（即细胞丢失、轴突发芽和突触重组）的齿状回进行细胞水平的研究。本文提供的初步数据表明，在GABAA受体介导的抑制缺失的情况下，大麻素可以抑制癫痫样放电，这种放电是由于匹罗卡品诱导TLE小鼠齿状回中新形成的复发性兴奋回路的激活引起的。利用电生理学、解剖学和分子生物学技术，假设：1)大麻素抑制新的复发性兴奋电路；2)大麻素直接抑制颗粒细胞，3)CB1R在TLE动物中表达上调，突触重组将在本实验室开发的小鼠TLE模型中进行测试。了解这些影响可能会促进为TLE患者设计更有效的治疗策略，这些患者的大脑经历了一定程度的突触重组。

DESCRIPTION (provided by applicant): A principal goal of epilepsy research is to identify and develop novel treatment strategies for seizure control that may be relatively selective for modulation of the synaptically reorganized circuitry in the epileptic brain. The objective of this Exploratory/Developmental (R21) research proposal is to identify the effects of exogenous and endogenous cannabinoids on neurons of the dentate gyrus in mice with pilocarpine-induced temporal lobe epilepsy (TLE), characterized by chronic spontaneous seizures, mossy fiber sprouting, and increased neuronal excitability and synchrony. The use of cannabinoids for treating seizure disorders has been proposed, but results of case study analyses have been mixed. The goal of this proposal is to determine how cannabinoids modulate activity in the dentate gyrus in a murine model of TLE in order to understand effects of the substance on a system that has undergone synaptic reorganization (versus effects on normal neural circuits). Most known central effects of cannabinoids are mediated by cannabinoid type 1 receptors (CB1R), usually located on presynaptic terminals. In the hippocampus, cannabinoids suppress synaptic input-especially feedback inhibition--to principal neurons, including dentate gyrus granule cells. Although cannabinoids appear to suppress some types of seizures, the cellular "disinhibitory" properties appear to be proconvulsive in normal brains. Recent analyses suggest that cannabinoids may suppress seizure activity in the epileptic brain. However, no studies at the cellular level have been performed in the dentate gyrus in an animal model of TLE (i.e., having cell loss, axon sprouting, and synaptic reorganization). Preliminary data presented here suggest that, in the absence of GABAA receptor-mediated inhibition, cannabinoids can inhibit epileptiform discharges that are attributable to activation of newly-formed recurrent excitatory circuitry in the dentate gyrus in mice with pilocarpine-induced TLE. Using electrophysiological, anatomical, and molecular biological techniques, the hypotheses that: 1) cannabinoids inhibit new recurrent excitatory circuitry; 2) cannabinoids inhibit granule cells directly, and 3) CB1R expression is upregulated in animals with TLE and synaptic reorganization will be tested in a murine model of TLE developed in this lab. Understanding these effects may promote more effective treatment strategies designed specifically for TLE patients, whose brains have undergone a degree of synaptic reorganization.