Airway mechanoreceptor deactivation.
Airway sensors play an important role in control of breathing. Recently, it was found that pulmonary slowly adapting stretch receptors (SARs) cease after a brief excitation following sodium pump blockade by ouabain. This deactivation can be explained by overexcitation. If this is true, mechanical stimulation of the SARs should also lead to a deactivation. In this study, we recorded unit activity of the SARs in anesthetized, open-chest, and mechanically ventilated rabbits and examined their responses to lung inflation at different constant pressures. Forty-seven of 137 units had a clear deactivation during the lung inflation. The deactivation threshold varied from unit to unit. For a given unit, the higher the inflation pressure, the sooner the deactivation occurs. For example, the SARs deactivated at 3.0 +/- 0.3 and 4.8 +/- 0.4 s when the lungs were inflated to constant pressures of 30 and 20 cmH(2)O, respectively (n = 25, P < 0.0001). The units usually ceased after a brief intense discharge. In some units, their activity shifted to a lower level, indicating a pacemaker switching. Our results support the notion that SARs deactivate due to overexcitation.
Guardiola
J
J
Dept. of Medicine, Univ. of Louisville, Louisville, KY 40292, USA.
Proctor
M
M
Li
H
H
Punnakkattu
R
R
Lin
S
S
Yu
J
J
D000200:Action Potentials / Q000502:physiology; D000818:Animals; D008168:Lung / Q000294:innervation / Q000502:physiology*; D008465:Mechanoreceptors / Q000502:physiology*; D040542:Mechanotransduction, Cellular / Q000502:physiology; D009130:Muscle, Smooth / Q000294:innervation / Q000502:physiology; D011661:Pulmonary Stretch Receptors / Q000502:physiology*; D011817:Rabbits