PHARMACOLOGICAL, PHYSIOLOGICAL,& BIOCHEMICAL AMYGDALA KINDLING & QUENCHING STUDY

这个项目的目标是了解和调节点火和淬火的过程。点燃是指在反复、间歇地给予亚抽搐刺激后出现抽搐。猝灭是我们实验室开发的一种程序，通过提高癫痫发作和/或后放电阈值来抑制点燃癫痫的发展和表达。这两种模型都涉及神经系统的长期变化；点燃可能持续动物的整个一生，而在停止手术后持续数周至数月的熄灭。不同的抗惊厥剂对点燃的影响与点燃发作的发展阶段(如发育期与完成期相比)和点燃刺激的类型(例如药物与电刺激)有关，表明这两个参数在抗惊厥反应性方面的重要性。具有特定生化靶点系统的药物已被用于阐明抗惊厥药物的作用机制，也已进行了研究以确定杏仁核点燃和猝灭的机制。到目前为止的重大发现包括以下几点的论证。1)根据点燃刺激的阶段和类型，出现不同的抗惊厥反应性模式；例如，卡马西平在杏仁核点燃的完成阶段是有效的抗惊厥剂，但在癫痫发展期间不是，慢性但非急性的卡马西平阻止局部麻醉剂点燃的癫痫(及其相关的致命性)的发展，但不是表现。2)胆碱能系统参与局麻药点燃，普鲁卡因和可卡因与利多卡因不同。阿托品可阻断普鲁卡因和可卡因诱发的癫痫发作，并增强利多卡因诱发的癫痫发作。毒扁豆碱可减弱利多卡因点燃。3)在杏仁核点燃的大鼠中，停止癫痫发作的一段时间会导致随后测试中的抗癫痫反应减弱，发作阈值降低(即，癫痫敏感性增加)，这表明癫痫诱导的内源性抗癫痫适应具有功能作用，这种适应似乎是短暂的，并有助于对外源性抗惊厥药物的反应。4)TRH是一种假说的内源性抗惊厥适应作用：在杏仁核点燃的大鼠，海马内注射TRH后，TRH呈剂量依赖性地减少后放电和癫痫持续时间。5)一些即刻早期基因、营养因子和多肽的mRNA表达在点燃过程中和完全或自发性癫痫发作后呈区域选择性增加。其中一些局部效应取决于诱发的后放电的长度；另一些则取决于刺激发生在杏仁核的哪个部位。6)在完全点燃的动物中，使用极低水平的直流电(LL)结合或不结合同时的低频刺激可以产生持久的后放电和癫痫阈值增加，并抑制点燃发展和癫痫的表达。这些阈值效应在停止猝灭刺激后持续数周至数月。7)猝灭与内嗅觉皮质和嗅周皮质苯二氮卓类受体结合增加有关，但不会增加一些即刻早期基因和TRH的mRNA表达。8)DC猝灭与胶质酸性腓肠肌蛋白的局部mRNA增加和银带沉积有关，这提出了一个问题，即LL-DC是否正在产生显微镜下的损害及其最终的临床相关性。9)树突状细胞也被用于杏仁核脑片的制备，其中它诱导同型突触而不是异型突触抑制，这种抑制可以通过增加刺激强度来克服。

The objectives of this project are to understand and modulate the processes of kindling and quenching. Kindling involves the development of convulsions following repeated, intermittent administration of a subconvulsant stimulation. Quenching is a procedure developed in our laboratory to inhibit the development and expression of kindled seizures by increasing the seizure and/or afterdischarge thresholds. Both models involve long-term changes in the nervous system; with kindling lasting possibly for the entire lifetime of the animal and quenching lasting for weeks to months after discontinuation of the procedure. The effects of various anticonvulsants on kindling have been examined in relation to stage of kindled seizure development (e.g., development vs. completed vs. spontaneous) and type of kindling stimulation (e.g., pharmacological vs. electrical), indicating the importance of both parameters in relation to anticonvulsant responsivity. Agents with specific biochemical target systems have been used to elucidate the mechanisms of action of anticonvulsants, and studies have also been conducted to determine mechanisms of amygdala kindling and quenching. Significant findings to date include demonstration of the following. 1) Distinct patterns of anticonvulsant responsivity occur based on the stage and type of kindling stimulation; e.g., carbamazepine is an effective anticonvulsant during the completed phase of amygdala kindling, but not during seizure development, and chronic, but not acute, carbamazepine blocks the development, but not expression, of local-anesthetic-kindled seizures (and their associated lethality). 2) The cholinergic system is involved in local anesthetic kindling and is distinct for procaine and cocaine compared with lidocaine. Atropine blocks seizures induced by procaine and cocaine and potentiates seizures induced by lidocaine. Physostigmine attenuates lidocaine kindling. 3) In amygdala-kindled rats, time off from seizures leads to a diminished anticon-vulsant response upon subsequent testing and a decrease in seizure threshold (i.e., increased seizure susceptibility), indicating a functional role for seizure-induced endogenous anticon-vulsant adaptations, which appear to be transient and to facilitate response to exogenous anticonvulsant agents. 4) TRH is one of the hypothesized endogenous anticonvulsant adaptations: following intrahippocampal administration, TRH dose-dependently attenuated the afterdischarge and seizure duration in amygdala-kindled rats. 5) The mRNA expression for a number of immediate early genes, trophic factors, and peptides is increased in a regionally selective manner during kindling development and after completed or spontaneous seizures. Some of these regional effects are dependent upon the length of the elicited afterdischarge; others are dependent on where in the amygdala the stimulation is occurring. 6) Quenching paradigms have been developed using very low levels (LL) of direct current (DC) with or without concurrent low frequency stimulation which produce a long-lasting increase in afterdischarge and seizure threshold, and an inhibition of kindling development and seizure expression in fully kindled animals. These threshold effects persisted for weeks to months after quenching stimulation was discontinued. 7) Quenching was associated with increases in benzodiazepine receptor binding in the entorhinal and perirhinal cortices, but did not produce increases in mRNA expression for a number of immediate early genes and TRH. 8) DC quenching is associated with local increases in the mRNA for glial acid fibulary protein and a strip of silver deposition, raising the question of whether a microscopic lesion is being produced by the LL-DC and of its ultimate clinical relevance. 9) DC has also been utilized in the amygdala slice preparation wherein it induces homosynaptic but not heterosynaptic inhibition that can be overridden by increasing intensity of stimulation.