Champagnat J, Denavit-Saubié M, Velluti J C
Brain Res. 1980 Jun 9;191(2):359-77. doi: 10.1016/0006-8993(80)91287-1.
The discharge of cat's bulbar respiratory neurones (RN) was shown to be modulated by periodic depressions which are characterized by their ability to reduce the effectiveness of microiontophoretically applied depolarizing agents: L-glutamate, acetylcholine and potassium. From the observation of cycle triggered time histograms (CTH), it appeared that these depressions have a determined and invariable phase relationship within the respiratory cycle. They were demonstrated in RN histologically located between and including the nucleus of the tractus solitarius and the nucleus ambiguus. Reproducibility and dose/response relationship of L-glutamate-induced depolarizations enabled an estimation of the functional effectiveness of these periodic depressions. In spontaneously phasic or 'silent' RN, depressions were demonstrated in the majority of cases (71%). Strongest depressions prevented spontaneous and L-glutamate-induced firing. Slighter depressions did not completely abolish L-glutamate effectiveness but reduced it by 20-90%. Conversely, in the majority of spontaneously tonic units (68%) depressions were not identified since the L-glutamate effect remained unchanged throughout the respiratory cycle. Four types of these respiration-related depressions were differentiated on the basis of their length, their phase relation to the respiratory cycle and their potentiation in barbiturate-anaesthetized preparations. A first type suppressed L-glutamate-evoked firing throughout inspiration; it was found in late-expiratory neurones. Two other types of depressions had a more restricted duration in the cycle: one was restricted to a portion of inspiration and was found in early-expiratory neurones; the other restricted to the beginning of expiration, was found in a special group of inspiratory neurones. A fourth type of inhibition was weaker and actively prolonged throughout expiration: it was found in another group of inspiratory neurones including the respiratory neurones located at the level of the nucleus of the tractus solitarius. These periodic depressions are interpreted in terms of synaptic inhibition; it is proposed that they play a major role in the functional organization of the respiratory centers at the bulbar level.
猫延髓呼吸神经元（RN）的放电显示受周期性抑制的调节，这些抑制的特点是能够降低微量离子电泳施加的去极化剂（L-谷氨酸、乙酰胆碱和钾）的有效性。从周期触发时间直方图（CTH）的观察来看，这些抑制在呼吸周期内具有确定且不变的相位关系。它们在组织学上位于孤束核和疑核之间（包括这两个核）的RN中得到证实。L-谷氨酸诱导的去极化的可重复性和剂量/反应关系使得能够估计这些周期性抑制的功能有效性。在自发呈相位性或“沉默”的RN中，大多数情况下（71%）都证实存在抑制。最强的抑制可阻止自发和L-谷氨酸诱导的放电。较轻的抑制不会完全消除L-谷氨酸的有效性，但会使其降低20% - 90%。相反，在大多数自发呈紧张性的单位中（68%）未发现抑制，因为L-谷氨酸的效应在整个呼吸周期中保持不变。根据这些与呼吸相关的抑制的时长、它们与呼吸周期的相位关系以及在巴比妥麻醉制剂中的增强作用，区分出了四种类型。第一种类型在整个吸气过程中抑制L-谷氨酸诱发的放电；它见于呼气后期的神经元。另外两种类型的抑制在周期中的持续时间更有限：一种局限于吸气的一部分，见于呼气早期的神经元；另一种局限于呼气开始时，见于一组特殊的吸气神经元。第四种类型的抑制较弱，在整个呼气过程中呈主动延长；它见于另一组吸气神经元，包括位于孤束核水平的呼吸神经元。这些周期性抑制被解释为突触抑制；有人提出它们在延髓水平呼吸中枢的功能组织中起主要作用。
