Changes of excitatory and inhibitory amino acid responses in the relay neurons of lateral geniculate nucleus by optic nerve denervation

为了阐明影响膝状背外侧核（LGNd）神经元活动的因素，我们分析了视神经去支配或不去支配动物新分离神经元的兴奋性和抑制性氨基酸受体的生理特性。(1)制备经注射逆行示踪剂DiI鉴定的LGNd神经元，在电压钳条件下采用制霉素穿孔贴片记录模式进行电生理研究。(2)兴奋性氨基酸对神经元的影响顺序为KA>NMDA>AMPA>Glu。(3) NAAG主要作用于NMDA受体，对非NMDA受体有弱的ka样作用。(4) nmda和ka诱导的Ca^<2+>对Cs^+的相对渗透率（Pc_a/Pc_S）分别为9.57和0.16。(5)细胞内C1^-浓度随年龄增长而增加：0-2日龄大鼠神经元浓度为35 mM， 2周龄大鼠神经元浓度为22 mM， 6月龄大鼠神经元浓度为15 mM。因此，GABA使未成熟大鼠的神经元去极化。(6)去神经支配诱导细胞内C1^-浓度升高，降低Mg^<2+>阻断NMDA反应。(7)利用“突触钮扣”制备的研究发现，在gaba能神经末梢存在NMDA、AMPA、KA受体。这些受体促进GABA从神经末梢释放。GABA_B和mGlu受体也存在于GABA能神经末梢，并作为自受体存在。

In order to clarify the factors contributing to the activities of dorsal lateral geniculate nucleus (LGNd) neurons, we analyzed the physiological properties of excitatory and inhibitory amino acid receptors of the neurons freshly dissociated from animals with or without optic nerve denervation.(1) The LGNd neurons identified by injection of a retrograde tracer, DiI,were prepared for the electrophysiological study using nystatin perforated patch recording mode under voltageclamp condition.(2) The effect of excitatory amino acids on the neurons was stronger in the order of KA>NMDA>AMPA>Glu.(3) A neurotransmitter candidate at retino-geniculate synapses, NAAG,mainly acted at NMDA receptors with a weak KA-like action on non-NMDA receptors.(4) The values of relative permeability of Ca^<2+> for Cs^+ (Pc_a/Pc_S) were 9.57 and 0.16 for NMDA-and KA-induced responses, respectively.(5) Intracellular C1^- concentration increased with aging : i. e. 35 mM for 0-2-day-old rat neuron, 22 mM for 2-week-old one, and 15 mM for 6-month-old one. Consequently, GABA depolarizes the neurons of immature rat.(6) Denervation induced the rise of intracellular C1^- concentration and also decreased Mg^<2+>blockade of NMDA response.(7) It was found in the study using 'synaptic bouton' preparation that NMDA,AMPA,KA receptors existed on GABAergic nerve endings. THese receptores facilitated tha GABA release from its nerve terminals. Both GABA_B and mGlu receptors also exist on GABA ergic nerve endigs and act as autoreceptors.