Serafin M, Khateb A, de Waele C, Vidal P P, Mühlethaler M
Département de Physiologie, CMU, Genève, Switzerland.
Exp Brain Res. 1992;88(1):187-92. doi: 10.1007/BF02259140.
We have recently shown in vivo that N-Methyl-D-Aspartate (NMDA) receptors are present in the guinea-pig vestibular complex and demonstrated that they are involved in the regulation of the resting discharge of vestibular neurones. A parallel in vitro study has identified in the guinea-pig medial vestibular nuclei (MVN) two main neuronal cell types, A and B MVNn, differing by their intrinsic membrane properties. One subtype of B MVNn was further characterized by the presence of a low threshold calcium spike (LTS). The present study investigated in vitro the responses of these different cell types to NMDA. Both A and B MVNn were depolarized by NMDA, which also induced a decrease in membrane resistance and an increase in the spontaneous firing rate. These effects could be blocked by D-AP5, a specific antagonist of NMDA receptors. Following a 10-30 mV hyperpolarization, a long-lasting oscillatory behavior could be induced in presence of NMDA. These oscillations were however restricted to the subtype of B MVNn without LTS. The NMDA-induced oscillations were tetrodotoxine-resistant, but could be eliminated by D-AP5 or by replacing sodium with choline. Functional implications of this oscillatory behavior are discussed.
我们最近在体内研究中表明，豚鼠前庭复合体中存在N-甲基-D-天冬氨酸（NMDA）受体，并证明它们参与前庭神经元静息放电的调节。一项平行的体外研究在豚鼠内侧前庭核（MVN）中鉴定出两种主要的神经元细胞类型，即A和B型MVN神经元，它们的内在膜特性不同。B型MVN神经元的一个亚型的特征是存在低阈值钙峰（LTS）。本研究在体外研究了这些不同细胞类型对NMDA的反应。A和B型MVN神经元均被NMDA去极化，这也导致膜电阻降低和自发放电率增加。这些效应可被NMDA受体的特异性拮抗剂D-AP5阻断。在超极化10 - 30 mV后，在存在NMDA的情况下可诱导出一种持久的振荡行为。然而，这些振荡仅限于没有LTS的B型MVN神经元亚型。NMDA诱导的振荡对河豚毒素具有抗性，但可被D-AP5或用胆碱替代钠消除。本文讨论了这种振荡行为的功能意义。
