Effects of CO₂ and hydrogen ions on the physical electrotonus of smooth muscle

Summary

Under the influence of a carbonate gas mixture (2/3−3/4O₂+1/3−1/4CO₂) the physical electrotonus (PE) of the circular smooth muscles of the frog stomach very quickly decreases 50–70%, while the excitability and spontaneous activity of the muscle are completely inhibited. These changes are quickly and easily reversible and are not connected with the action on the muscle of H⁺ forming under the influence of CO₂ inasmuch as in a deliberately acidic Ringer's solution with pH reduced to a level close to that seen after the passage of a carbonate gas mixture, the PE at first slightly increases and then very slowly and only insignificantly lessens. Changes in the electrical properties of the smooth muscle, and, in particular, the decline of the PE under the influence of the carbonate gas mixture are apparently associated with the direct specific action of CO₂ on the permeability of the protoplasmatic membrane.