The effect on breathing of abruptly reducing the discharge of central chemoreceptors.

Tris, a powerful CO2 buffer, was injected through one vertebral artery directly at the central chemoreceptive region in bilaterally vagotomized pentobarbitone anaesthetized cats. This was intended to reduce central chemoreceptor drive abruptly. Injections in inspiration shortened that inspiration and prolonged the following expiration. Injections given early in expiration often prolonged that expiration and also the following inspiration, but most injections given in an expiration shortened that expiration and also shortened the following inspiration. Tidal volume (VT) was invariably reduced. A plot of VT against delay from an injection to the termination of inspiration shows that VT falls with a half time of about one second. The changes in the pattern of breathing were similar to those after abrupt removal of carotid body chemoreceptor discharge (Nye et al., 1981) though the latency to the first response of air flow was about 100 msec longer. These observations support the idea that peripheral and central chemoreceptors have similar connections with the respiratory centre.