Journal of Applied Physiology, Vol 41, Issue 5 612-622, Copyright © 1976 by American Physiological Society
Integration of chemoreceptor stimuli by caudal pontile and rostral medullary sites
W. M. St John and S. C. Wang
Ventilatory regulation by pontile pneumotaxic and apneustic centers and by
rostral medullary sites was evaluated in intercollicular decerebrate cats.
Following pneumotaxic center ablation, PAco2 was significantly elevated.
Moreover, in response to hypercapina or hypoxia, frequency responses were
significantly diminished whereas tidal volume responses were unchanged or
elevated. Interruption of apneustic center function by caudal pontile
transection or radiofrequency lesions in the caudal pons and/or rostral
medulla resulted in significant decreases of tidal volume responses and
significant elevations of frequency responses to both hypercapnia and
hypoxia. Neither minute volume responses nor the PAco2 level was altered.
It is concluded that the apneustic center exercises a primary role in the
brainstem definition of tidal volume responses for both peripheral and
central chemoreceptor afferent stimuli. The apneustic center is also
considered to exert an impoetant function in the definition of respiratory
frequency. A medially placed pathway in the rostral medulla is proposed to
interconnect the apneustic center with the medullary respiratory nuclei.
