Facilitation and inhibition of the medullary respiratory neurones.

Abstract

1.Effects of the mesencephalic reticular stimulation were observed on the medullary respiratory discharges of the urethanized rabbits. Both inspiratory and expiratory neurones were facilitated by the medial mesencephalic stimulation.Inhibition was observed during the lateral stimulation. The rate of breathing increased either by facilitation or by inhibition of the respiratory discharges. The action of the midbrain is assumed to cause the simultaneous facilitation or simultaneous inhibition of both inspiratory and expiratory neurones.2. Respiratory discharges were recorded from the medulla of the urethanized cats during local heating of the preoptic region. With the onset of heating, the respiratory rate and the rate of respiratory discharges are slightly decreased at first and then increased. The mode of the neuronal responses to hypothalamic heating was identical with that of the responses to midbrain stimulation.3. In the gasping, which resulted from the transection of the rostral medulla, expiratory bursts gave way to a continuous firing in which the discharge frequency remained unchanged. The appearance of inspiratory discharges was inhibited. These figures were similar to those of expiratory responses from vagal stimulation at high frequency.4. During apneustic breathing induced by the pontine transection and vagotomy, medullary expiratory discharges were inhibited and inspiratory neurones fired continuously but in a control frequency. The apneusis is just like the inspiratory response to low-frequency vagal stimulation, as far as the changes of respiratory discharges are concerned.5. Based on these results, two inhibitory systems were proposed in the brainstem, that is, the inspiration- and the expiration-inhibitory system.Neural, organization of the respiratory periodicity was briefly discussed as well.