Induction of a myogenic response in tonic airway smooth muscle by tetraethylammonium

Am J Physiol. 1975 Feb;228(2):628-32. doi: 10.1152/ajplegacy.1975.228.2.628.


In multi-unit tracheal smooth muscle (TSM), quick stretches applied at a velocity of 5 times the measured maximum velocity of isotonic shortening of the muscle, of a magnitude 3 times the measured extension of the series-elastic component when the muscle contracts maximally, and at optimal muscle length (L-o) were unable to elicit any myogenic response (MR). Experimental conditions such as hypoxia (P-O2 smaller than 60 mmHg) and acidosis (pH equals 6.8) or the presence of Ba2+ (2 mM), acetylcholine (10-6 M), or high (K+)-o (59 mM) were also unable to elicit the MR. However, tetraethylammonium chloride (TEA, 0.4-67 mM) produces 1) spontaneous phasic contractions and 2) a MR to quick stretch. The ionic basis for these changes was then investigated by studying the Ca and Mg dependence of the response to TEA. The dose-response relationship to TEA was shifted to the left by decreasing external Mg2+ from 2.5 to 0.5 mM. The ability of TSM to produce a MR was absolutely dependent on external Ca, but the threshold concentration required shifted from 2.5 times 10-5 M at normal external Mg (2.5 mM) to 5 times 10-4 M at the reduced external Mg (0.5 mM). The effects of TEA on spontaneity and the MR were abolished by D-600. These results suggest that 1) TEA functionally converts multiunit smooth muscle into a single unit one and leads to the development of a MR and 2) the MR results from a depolarization-activated mobilization of Ca and is inhibited by ionic conditions known to increase membrane permeability.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Acetylcholine / pharmacology
  • Animals
  • Barium / pharmacology
  • Biomechanical Phenomena*
  • Calcium / pharmacology
  • Dogs
  • Dose-Response Relationship, Drug
  • Guinea Pigs
  • Hydrogen-Ion Concentration
  • Hypoxia
  • In Vitro Techniques
  • Magnesium / pharmacology
  • Muscle Contraction / drug effects
  • Muscle, Smooth / drug effects
  • Muscle, Smooth / physiology*
  • Physical Stimulation
  • Potassium / pharmacology
  • Tetraethylammonium Compounds / pharmacology*
  • Trachea / physiology*
  • Transducers


  • Tetraethylammonium Compounds
  • Barium
  • Magnesium
  • Acetylcholine
  • Potassium
  • Calcium