Connexins are transmembrane proteins that form hemichannels allowing the exchange of molecules between the extracellular space and the cell interior. Two hemichannels from adjacent cells dock and form a continuous gap junction pore, thereby permitting direct intercellular communication. Connexin 36 (Cx36), expressed primarily in neurons, is involved in the synchronous activity of neurons and may play a role in aberrant synchronous firing, as seen in seizures. To understand the reciprocal interactions between Cx36 and seizure-like neural activity, we examined three questions: (a) does Cx36 deficiency affect seizure susceptibility, (b) does seizure-like activity affect Cx36 expression patterns, and (c) does acute blockade of Cx36 conductance increase seizure susceptibility. We utilize the zebrafish pentylenetetrazol [PTZ; a GABA(A) receptor antagonist] induced seizure model, taking advantage of the compact size and optical translucency of the larval zebrafish brain to assess how PTZ affects brain-wide neuronal activity and Cx36 protein expression. We exposed wild-type and genetic Cx36-deficient (cx35.5-/-) zebrafish larvae to PTZ and subsequently mapped neuronal activity across the whole brain, using phosphorylated extracellular-signal-regulated kinase (pERK) as a proxy for neuronal activity. We found that cx35.5-/- fish exhibited region-specific susceptibility and resistance to PTZ-induced hyperactivity compared to wild-type controls, suggesting that genetic Cx36 deficiency may affect seizure susceptibility in a region-specific manner. Regions that showed increased PTZ sensitivity include the dorsal telencephalon, which is implicated in human epilepsy, and the lateral hypothalamus, which has been underexplored. We also found that PTZ-induced neuronal hyperactivity resulted in a rapid reduction of Cx36 protein levels within 30 min. This Cx36 reduction persists after 1-h of recovery but recovered after 3–6 h. This acute downregulation of Cx36 by PTZ is likely maladaptive, as acute pharmacological blockade of Cx36 by mefloquine results in increased susceptibility to PTZ-induced neuronal hyperactivity. Together, these results demonstrate a reciprocal relationship between Cx36 and seizure-associated neuronal hyperactivity: Cx36 deficiency contributes region-specific susceptibility to neuronal hyperactivity, while neuronal hyperactivity-induced downregulation of Cx36 may increase the risk of future epileptic events.

连接蛋白是形成半通道的跨膜蛋白，允许细胞外空间和细胞内部之间的分子交换。来自相邻细胞的两个半通道停靠并形成连续的间隙连接孔，从而允许直接的细胞间通讯。连接蛋白36（Cx36）主要在神经元中表达，参与神经元的同步活动，并可能在癫痫发作中异常同步放电中起作用。为了了解Cx36与癫痫样神经活动之间的相互关系，我们研究了三个问题：（a）Cx36缺乏会影响癫痫易感性吗？（b）癫痫样活动是否会影响Cx36的表达模式，以及（c）急性阻断Cx36电导增加癫痫发作敏感性。我们利用斑马鱼戊四氮[PTZ; [GABA（A）受体拮抗剂]诱导的癫痫发作模型，利用斑马鱼幼虫大脑的紧凑大小和光学半透明性来评估PTZ如何影响大脑范围的神经元活性和Cx36蛋白表达。我们暴露了野生型和遗传性Cx36缺陷（cx35.5-/-斑马鱼幼虫到PTZ，然后使用磷酸化的细胞外信号调节激酶（pERK）作为神经元活动的代理，在整个大脑中绘制神经元活动。我们发现cx35.5-/-与野生型对照组相比，鱼表现出区域特异性敏感性和对PTZ诱导的过度活跃的抵抗力，这表明遗传性Cx36缺乏症可能以区域特异性方式影响癫痫发作的敏感性。显示PTZ敏感度增加的区域包括牵涉到人类癫痫症的背端脑和未充分探究的下丘脑外侧。我们还发现PTZ诱导的神经元过度活跃导致30分钟内Cx36蛋白水平快速降低。这种Cx36降低在恢复1小时后仍然存在，但在3-6小时后恢复。PTZ对Cx36的这种急性下调可能是适应不良的，因为甲氟喹对Cx36的急性药理作用导致对PTZ诱导的神经元过度活跃的敏感性增加。一起，