Wolszon L R, Pereda A E, Faber D S
Department of Neurobiology and Anatomy, MCP Hahnemann School of Medicine, Allegheny University of the Health Sciences, Philadelphia, Pennsylvania 19129, USA.
J Neurophysiol. 1997 Nov;78(5):2693-706. doi: 10.1152/jn.1997.78.5.2693.
A fast synaptic potential mediated by NMDA and non-NMDA receptors. J. Neurophysiol. 78: 2693-2706, 1997. Excitatory synaptic transmission in the CNS often is mediated by two kinetically distinct glutamate receptor subtypes that frequently are colocalized, the N-methyl--aspartate (NMDA) and non-NMDA receptors. Their synaptic currents are typically very slow and very fast, respectively. We examined the pharmacological and physiological properties of chemical excitatory transmission at the mixed electrical and chemical synapses between auditory afferents and the goldfish Mauthner cell, in vivo. Previous physiological data have suggested the involvement of glutamate receptors in this fast excitatory postsynaptic potential (EPSP), the chemical component of which decays with a time constant of <2 ms. We demonstrate here that the pharmacological and voltage-dependent characteristics of the synaptic currents are consistent with glutamatergic transmission and that both NMDA and non-NMDA receptors are involved. The two components surprisingly exhibit quite similar kinetics even at resting potential, with the NMDA response being only slightly slower. Due to its fast kinetics and characteristic voltage dependence, NMDA receptor-mediated transmission at these first-order synapses contributes significantly to paired pulse and frequency-dependent facilitation of successive fast EPSPs during high-frequency repetitive firing, a presynaptic impulse pattern that induces activity-dependent homosynaptic changes in both electrical and chemical transmission. Thus NMDA receptor kinetics in this intact preparation are suited to its functional requirements, namely speed of information transmission and the ability to trigger changes in synaptic efficacy.
一种由NMDA和非NMDA受体介导的快速突触电位。《神经生理学杂志》78: 2693 - 2706, 1997年。中枢神经系统中的兴奋性突触传递通常由两种动力学特性不同且常共定位的谷氨酸受体亚型介导，即N - 甲基 - D - 天冬氨酸（NMDA）受体和非NMDA受体。它们的突触电流通常分别非常缓慢和非常快速。我们在体内研究了听觉传入神经与金鱼Mauthner细胞之间混合电突触和化学突触处化学性兴奋性传递的药理学和生理学特性。先前的生理学数据表明谷氨酸受体参与了这种快速兴奋性突触后电位（EPSP），其化学成分以小于2毫秒的时间常数衰减。我们在此证明，突触电流的药理学和电压依赖性特征与谷氨酸能传递一致，并且NMDA和非NMDA受体均参与其中。令人惊讶的是，即使在静息电位下，这两个成分也表现出相当相似的动力学，NMDA反应仅稍慢一些。由于其快速的动力学和特征性的电压依赖性，在这些一级突触处由NMDA受体介导的传递在高频重复放电期间对相继快速EPSP的成对脉冲和频率依赖性易化有显著贡献，这种突触前冲动模式在电传递和化学传递中均诱导与活动相关的同突触变化。因此，在这种完整标本中，NMDA受体动力学符合其功能需求，即信息传递速度和触发突触效能变化的能力。
