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控制癫痫发作的新治疗策略，该策略对于调节癫痫大脑中的突触重组电路可能具有相对选择性。这项探索性/开发性（R21）研究计划的目的是确定外源性和内源性大麻素对毛果芸香碱诱导的颞叶癫痫（TLE）小鼠齿状回神经元的影响，其特征是慢性自发性癫痫发作、苔藓纤维出芽以及神经元兴奋性和同步性增加。有人提议使用大麻素来治疗癫痫症，但案例研究分析的结果好坏参半。该提案的目标是确定大麻素如何调节 TLE 小鼠模型中齿状回的活动，以便了解该物质对经过突触重组的系统的影响（相对于对正常神经回路的影响）。大麻素最知名的中枢作用是由 1 型大麻素受体 (CB1R) 介导的，通常位于突触前末端。在海马体中，大麻素抑制对主要神经元（包括齿状回颗粒细胞）的突触输入，尤其是反馈抑制。尽管大麻素似乎可以抑制某些类型的癫痫发作，但细胞的“去抑制”特性似乎在正常大脑中具有促惊厥作用。最近的分析表明，大麻素可能会抑制癫痫大脑的癫痫发作活动。然而，尚未在 TLE 动物模型（即细胞丢失、轴突萌芽和突触重组）的齿状回中进行细胞水平的研究。这里提供的初步数据表明，在没有 GABAA 受体介导的抑制作用的情况下，大麻素可以抑制癫痫样放电，这种放电可归因于毛果芸香碱诱导的 TLE 小鼠齿状回中新形成的周期性兴奋回路的激活。利用电生理学、解剖学和分子生物学技术，提出以下假设：1) 大麻素抑制新的周期性兴奋回路； 2) 大麻素直接抑制颗粒细胞，3) 患有 TLE 的动物中 CB1R 表达上调，并且将在本实验室开发的 TLE 小鼠模型中测试突触重组。了解这些影响可能会促进专为 TLE 患者设计更有效的治疗策略，这些患者的大脑已经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.