Sundaresan Karthik, Ziemann Ulf, Stanley Jeff, Boutros Nash
Department of Psychiatry and Behavioral Neurosciences, School of Medicine, Wayne State University, USA.
Neuroreport. 2007 Feb 12;18(3):289-92. doi: 10.1097/WNR.0b013e3280143cf0.
Prior transcranial magnetic stimulation studies showed that resting motor threshold is elevated in abstinent cocaine-dependent patients, suggesting a decrease in axonal excitability. In contrast, the increased incidence of seizures and psychosis in this group suggests increased excitability or decreased inhibition. Here, we studied long-interval intracortical facilitation and long-interval intracortical inhibition, paired-pulse transcranial magnetic stimulation measures that are more directly linked to glutamatergic cortical facilitation and GABAergic inhibition, respectively. Ten cocaine-dependent and 10 healthy controls were examined. Resting motor threshold, long-interval intracortical facilitation and long-interval intracortical inhibition were tested from the left motor cortex. The cocaine group showed an elevated resting motor threshold and an increased long-interval intracortical facilitation, whereas long-interval intracortical inhibition was normal. Although the increase in long-interval intracortical facilitation suggests exaggerated cortical glutamatergic excitability, the increase in resting motor threshold may signify a protective mechanism against seizures and psychosis.
先前的经颅磁刺激研究表明，戒断的可卡因依赖患者静息运动阈值升高，提示轴突兴奋性降低。相比之下，该组癫痫发作和精神病发病率增加表明兴奋性增加或抑制作用降低。在此，我们研究了长时程皮质内易化和长时程皮质内抑制，这两种成对脉冲经颅磁刺激测量方法分别与谷氨酸能皮质易化和γ-氨基丁酸能抑制更直接相关。对10名可卡因依赖者和10名健康对照者进行了检查。从左侧运动皮质测试静息运动阈值、长时程皮质内易化和长时程皮质内抑制。可卡因组静息运动阈值升高，长时程皮质内易化增加，而长时程皮质内抑制正常。虽然长时程皮质内易化增加提示皮质谷氨酸能兴奋性过高，但静息运动阈值升高可能意味着对癫痫发作和精神病的一种保护机制。
