Journal of Applied Physiology, Vol 64, Issue 4 1369-1375, Copyright © 1988 by American Physiological Society
Rapid and transient excitation of respiration mediated by central chemoreceptor
H. Arita, N. Kogo and K. Ichikawa
Institute of Basic Medical Sciences, University of Tsukuba, Ibaraki, Japan.
We evaluated rapid and transient changes in phrenic nerve (PN) and internal
intercostal (IIC) activities when 0.2-0.5 ml of saline saturated with 100%
CO2 was injected into the vertebral artery during various respiratory
phases in decerebrated spontaneously breathing cats. The injections evoked
an initial transient inhibition of ongoing PN or IIC activity with a mean
onset latency of 0.17 s, followed by excitation of subsequent respiratory
activities with an onset latency ranging from 0.4 to 2.7 s; the average
onset latency of expiratory excitation (1.49 s) was significantly longer
than that of inspiratory facilitation (0.89 s). The initial inhibitory
responses were analogous to reflex effects of injections of phenyl
biguanide, indicating that the initial inhibition was due to activation of
vascular nociceptors and the subsequent excitation was due to stimulation
of the central chemoreceptors. In addition, CO2-saline injections during
hypocapnic apnea developed a quick reappearance of respiratory rhythm, and
the first facilitatory effect appeared in tonic IIC activity, which became
more active before rhythm started. In summary, the present study, by use of
a technique of vertebral arterial injections of 100% CO2-saline, revealed
dynamic properties of respiratory control system mediated by central
chemoreceptors and vascular nociceptors.
