Paré D, Lebel E, Lang E J
Département de Physiologie, Faculté de Médecine, Université Laval, Quebec, Canada.
J Neurophysiol. 1997 Sep;78(3):1735-9. doi: 10.1152/jn.1997.78.3.1735.
We studied the impact of transmitter release resistant to tetrodotoxin (TTX) in morphologically identified neocortical pyramidal neurons recorded intracellularly in barbiturate-anesthetized cats. It was observed that TTX-resistant release occurs in pyramidal neurons in vivo and at much higher frequencies than was previously reported in vitro. Further, in agreement with previous findings indicating that GABAergic and glutamatergic synapses are differentially distributed in the somata and dendrites of pyramidal cells, we found that most miniature synaptic potentials were sensitive to gamma-aminobutyric acid-A (GABA(A)) or alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) antagonists in presumed somatic and dendritic impalements, respectively. Pharmacological blockage of spontaneous synaptic events produced large increases in input resistance that were more important in dendritic (approximately 50%) than somatic (approximately 10%) impalements. These findings imply that in the intact brain, pyramidal neurons are submitted to an intense spike-independent synaptic bombardment that decreases the space constant of the cells. These results should be taken into account when extrapolating in vitro findings to intact brains.
我们研究了对河豚毒素（TTX）具有抗性的递质释放对在巴比妥类麻醉猫中细胞内记录的形态学鉴定的新皮质锥体神经元的影响。据观察，对TTX具有抗性的释放发生在体内的锥体神经元中，且频率比先前在体外报道的要高得多。此外，与先前表明GABA能和谷氨酸能突触在锥体细胞的胞体和树突中分布不同的研究结果一致，我们发现，在假定的胞体和树突刺入记录中，大多数微小突触电位分别对γ-氨基丁酸-A（GABA(A)）或α-氨基-3-羟基-5-甲基-4-异恶唑丙酸（AMPA）拮抗剂敏感。对自发突触事件的药理学阻断导致输入电阻大幅增加，这在树突刺入记录中（约50%）比在胞体刺入记录中（约10%）更为显著。这些发现表明，在完整大脑中，锥体神经元受到强烈的与动作电位无关的突触轰击，这会减小细胞的空间常数。在将体外研究结果外推至完整大脑时，应考虑这些结果。
