Journal of Applied Physiology, Vol 62, Issue 3 932-940, Copyright © 1987 by American Physiological Society
Respiration in awake cats: sympathectomy and deafferentation of carotid bifurcations
P. C. Szlyk and D. B. Jennings
Respiratory effects of sympathectomy of the carotid bifurcations and, in a
subsequent experiment, bilateral carotid sinus nerve section were examined
in six awake resting cats. In each intact and denervated state, sequential
breaths were analyzed at 10-min intervals up to 80 min. Individual breath
frequency (f), tidal volume (VT), and ventilation (V = f X VT) were
determined. In individual cats, sympathectomy or deafferentation could
cause significant increases or decreases in ventilation or no change. Thus
the range of spontaneous variability in breath V as well as minute
ventilation (VE), averaged for the group, were not consistently altered in
the same direction by either sympathectomy or deafferentation of the
carotid bifurcations. Interestingly, in most cats after both sympathectomy
(5 of 6) and deafferentation (4 of 6), VT increased and f decreased
relative to V. Despite this, after sinus nerve section in two cats arterial
PO2 decreased and arterial PCO2 tended to increase relative to VE,
suggesting possible effects of deafferentation on ventilation-perfusion
balance. Sympathectomy also affected timing such that inspiratory time
began to exceed 0.5 of the breath duration at a lower breath f; this effect
of sympathectomy was reversed to intact values by subsequent sinus
deafferentation. Thus, in eupneic awake cats, sympathetics normally
suppress reflex modulation of central timing from carotid chemoreceptors
and/or baroreceptors.
