Voss Logan J, Jacobson Gregory, Sleigh James W, Steyn-Ross Alistair, Steyn-Ross Moira
Department of Anesthesiology, Waikato Clinical School, University of Auckland, Waikato Hospital, New Zealand.
Epilepsia. 2009 Aug;50(8):1971-8. doi: 10.1111/j.1528-1167.2009.02087.x. Epub 2009 Apr 19.
The role of gap junctions in seizures is an area of intense research. Many groups have reported anticonvulsant effects of gap junction blockade, strengthening the case for a role for gap junctions in ictogenesis. The cerebral cortex is underrepresented in this body of research. We have investigated the effect of gap junction blockade on seizure-like activity in rat and mouse cerebral cortex slices.
Seizure-like activity was induced by perfusing with low-magnesium artificial cerebrospinal fluid. The effect of three gap junction blockers was investigated in rat cortical slices; quinine (200 and 400 microm), quinidine (100 and 200 microm), and carbenoxolone (100 and 200 microm). In addition, the effect of mefloquine was investigated in wild-type mice and connexin36 knockout mice. The data were analyzed for the effect on frequency and amplitude of seizure-like events.
Paradoxical excitatory effects on seizure-like activity were observed for all three agents in rat cortical slices. Quinine (200 microm) and carbenoxolone (100 microm) increased both the frequency and amplitude of seizure-like events. Quinidine (100 microm) increased the frequency of events. Higher doses of quinine (400 microm) and carbenoxolone (200 microm) had biphasic excitatory-inhibitory effects. Similar excitatory effects were observed in adult wild-type mouse cortical slices perfused with mefloquine (5 microm or 10 microm), but were absent in slices from connexin36-deficient mice.
In conclusion, we have shown a paradoxical proseizure effect of pharmacologic gap junction blockade in a cortical model of seizure-like activity. We suggest that this effect is probably due to a disruption of inhibitory interneuron coupling secondary to connexin36 blockade.
缝隙连接在癫痫发作中的作用是一个深入研究的领域。许多研究小组报告了缝隙连接阻断的抗惊厥作用，这进一步证明了缝隙连接在癫痫发作形成过程中发挥作用。在这一研究领域中，大脑皮层的研究相对较少。我们研究了缝隙连接阻断对大鼠和小鼠大脑皮层切片中癫痫样活动的影响。
通过灌注低镁人工脑脊液诱导癫痫样活动。研究了三种缝隙连接阻滞剂对大鼠皮层切片的影响；奎宁（200和400微摩尔）、奎尼丁（100和200微摩尔）和甘草次酸（100和200微摩尔）。此外，还研究了甲氟喹对野生型小鼠和连接蛋白36基因敲除小鼠的影响。分析数据以观察其对癫痫样事件频率和幅度的影响。
在大鼠皮层切片中，观察到所有三种药物对癫痫样活动均有矛盾的兴奋作用。奎宁（200微摩尔）和甘草次酸（100微摩尔）增加了癫痫样事件的频率和幅度。奎尼丁（100微摩尔）增加了事件的频率。更高剂量的奎宁（400微摩尔）和甘草次酸（200微摩尔）具有双相兴奋-抑制作用。在用甲氟喹（5微摩尔或10微摩尔）灌注的成年野生型小鼠皮层切片中观察到类似的兴奋作用，但在连接蛋白36缺陷小鼠的切片中未观察到。
总之，我们在癫痫样活动的皮层模型中显示了药理学缝隙连接阻断的矛盾促癫痫作用。我们认为这种作用可能是由于连接蛋白36阻断继发的抑制性中间神经元耦合破坏所致。
