Grelot L, Iscoe S, Bianchi A L
Département de Physiologie et Neurophysiologie, Faculté des Sciences et Techniques Saint-Jérôme, C.N.R.S. UA 205, Marseille, France.
Brain Res. 1988 Mar 8;443(1-2):27-36. doi: 10.1016/0006-8993(88)91595-8.
The effects of inhibitory (gamma-aminobutyric acid (GABA) and glycine) and excitatory (L-glutamate and DL-homocysteate, DLH) amino acids on the excitability of respiratory bulbospinal neurons were studied in decerebrate, paralyzed, bilaterally vagotomized, artificially ventilated cats. Unit activities were recorded extracellularly in the medulla in both the ventrolateral portion of the nucleus tractus solitarius and the para-ambigual region in the vicinity of the nucleus ambiguus (dorsal and ventral respiratory groups, respectively). All neurons were bulbospinal since they could be antidromically activated by electrical stimuli to the spinal cord. We used variations in antidromic latency (ADL) as a measure of changes in excitability of the soma. All neurons exhibited variations in ADL related to the respiratory cycle, being shortest (minimum ADL) during neural activity and longest (maximum ADL) in the silent period. Neurons whose discharge frequencies fell during application of putative inhibitory amino acids showed an increase of minimum ADL compared to control, indicating hyperpolarization. Minimum ADL, in some cells, became shorter during application of excitatory amino acids, indicating depolarization; in others, mechanisms secondary to increased neuronal firing likely obscured their effects. The transient maximum ADL usually present at the onset of the silent period was increased by excitatory amino acids and, in some units, was reduced or eliminated by inhibitory amino acids. These effects are discussed in terms of a modulation by synaptic inputs and neurotransmitters of the cumulative afterhyperpolarization which follows bursts of action potentials.
在去大脑、麻痹、双侧迷走神经切断、人工通气的猫身上，研究了抑制性（γ-氨基丁酸（GABA）和甘氨酸）和兴奋性（L-谷氨酸和DL-高半胱氨酸，DLH）氨基酸对呼吸球脊髓神经元兴奋性的影响。在延髓孤束核腹外侧部分和疑核附近的旁疑核区域（分别为背侧和腹侧呼吸组）细胞外记录单位活动。所有神经元都是球脊髓神经元，因为它们可被脊髓电刺激逆向激活。我们将逆向潜伏期（ADL）的变化作为衡量胞体兴奋性变化的指标。所有神经元的ADL都随呼吸周期而变化，在神经活动期间最短（最小ADL），在静息期最长（最大ADL）。在应用假定的抑制性氨基酸期间放电频率下降的神经元，与对照组相比，最小ADL增加，表明超极化。在一些细胞中，应用兴奋性氨基酸期间最小ADL变短，表明去极化；在另一些细胞中，神经元放电增加继发的机制可能掩盖了它们的作用。静息期开始时通常出现的短暂最大ADL，在应用兴奋性氨基酸后增加，在一些单位中，抑制性氨基酸可使其降低或消除。根据突触输入和神经递质对动作电位爆发后累积的超极化后电位的调制来讨论这些效应。
