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Effects of potassium channel blockers on CO2-induced slowly adapting pulmonary stretch receptor inhibition

S Matsumoto1, T Takahashi, T Tanimoto

  • 1Department of Physiology, Nippon Dental University, School of Dentistry at Tokyo, Tokyo, Japan.

The Journal of Pharmacology and Experimental Therapeutics
|August 24, 1999
PubMed

Insights

Carbon dioxide (CO(2)) inhalation inhibits pulmonary stretch receptor (SAR) activity in rabbits, particularly during exhalation. This effect is mediated by 4-aminopyridine-sensitive potassium channels in SAR nerve terminals.

Area of Science:

  • Physiology
  • Respiratory System Regulation
  • Neuroscience

Background:

  • Pulmonary stretch receptors (SARs) are crucial for regulating breathing.
  • The effects of carbon dioxide (CO(2)) on SAR activity are not fully understood.
  • Investigating CO(2)'s impact on SARs can reveal mechanisms of respiratory control.

Purpose of the Study:

  • To investigate the inhibitory effects of CO(2) inhalation on SAR activity in rabbits.
  • To determine the role of potassium (K(+)) channels in mediating CO(2)'s effect on SARs.
  • To elucidate the specific K(+) channels involved in CO(2)-induced SAR inhibition.

Main Methods:

  • Studied anesthetized, artificially ventilated rabbits with vagotomies.
  • Administered CO(2) gas mixtures and measured SAR activity and tracheal pressure (P(T)).
  • Used intravenous 4-aminopyridine and tetraethylammonium (K(+) channel blockers) to assess their effects on CO(2) responses.

Main Results:

  • CO(2) inhalation decreased SAR activity during both inflation and deflation, with a greater effect during deflation.
  • CO(2) did not alter P(T), indicating no change in bronchomotor tone.
  • 4-aminopyridine dose-dependently blocked the inhibitory effect of CO(2) on SARs.
  • Tetraethylammonium did not affect the inhibitory responses to CO(2).

Conclusions:

  • CO(2) inhalation inhibits SAR activity via a mechanism involving 4-aminopyridine-sensitive K(+) channels.
  • These K(+) channels are likely located in the nerve terminals of SARs.
  • Findings suggest a novel pathway for CO(2) in modulating respiratory reflexes.

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