Ikegaya Y, Yoshida M, Saito H, Nishiyama N
Department of Chemical Pharmacology, Faculty of Pharmaceutical Sciences, University of Tokyo, Japan.
J Pharmacol Exp Ther. 1997 Jan;280(1):471-6.
Hippocampal slice from early postnatal rat was used to elucidate the influence of epileptic activity elicited by picrotoxin on synapse formation of mossy fibers. Neurite reelongation and synaptogenesis of mossy fibers transected at 8 days in vitro were confirmed by staining with Dil, a fluorescent membrane dye used as a neuronal tracer, and by recording field excitatory postsynaptic potentials (fEPSP) in the CA3 region evoked by stimulation of the dentate gyrus. Picrotoxin (50 microM), which evoked spontaneous epileptiform firing in the CA3 region that was occluded by tetrodotoxin (1 microM), hindered development of fEPSP amplitude after a lesion of mossy fibers. Furthermore, observations using a Timm method, a histochemical technique that preferentially labels synaptic terminals of mossy fibers, revealed that picrotoxin prevented synaptogenesis in the CA3 region. This inhibitory effect of picrotoxin was completely abolished by tetrodotoxin or nicardipine (10 microM), a L-type calcium channel blocker, but not by 2-amino-5-phosphonopentanoic acid (50 microM), a N-methyl-D-aspartate receptor antagonist, suggesting that influx of calcium ion via L-type calcium channels during epileptic bursts mediated the disturbance of appropriate synapse formation of mossy fibers.
使用出生后早期大鼠的海马切片来阐明由印防己毒素引发的癫痫活动对苔藓纤维突触形成的影响。通过用Dil（一种用作神经元示踪剂的荧光膜染料）染色以及记录刺激齿状回在CA3区诱发的场兴奋性突触后电位（fEPSP），证实了体外培养8天时横断的苔藓纤维的神经突重新伸长和突触发生。印防己毒素（50微摩尔）在CA3区诱发自发癫痫样放电，该放电可被河豚毒素（1微摩尔）阻断，它在苔藓纤维损伤后阻碍了fEPSP幅度的发展。此外，使用Timm方法（一种优先标记苔藓纤维突触终末的组织化学技术）进行的观察显示，印防己毒素阻止了CA3区的突触发生。印防己毒素的这种抑制作用可被河豚毒素或尼卡地平（10微摩尔，一种L型钙通道阻滞剂）完全消除，但不能被N-甲基-D-天冬氨酸受体拮抗剂2-氨基-5-磷酸戊酸（50微摩尔）消除，这表明癫痫发作期间通过L型钙通道的钙离子内流介导了苔藓纤维适当突触形成的紊乱。
