Excitation and contraction in bovine tracheal smooth muscle.

Abstract

SUMMARY1. The smooth muscle layer of the bovine trachea was studied in vitro with the micro-electrode and sucrose-gap techniques. The membrane potential was stable at -47-6 + 0-98 (S.E. of mean) mV, and there was no spontaneous electrical or mechanical activity.2. The cell membrane had strong rectifying properties, making it impossible to elicit action potentials by electrical stimulation in normal Krebs solution. The rectification was abolished by TEA (30 mmol/l), which depolarized the membrane and produced plateau-type action potentials.3. The spontaneous repetitive action potentials produced by TEA were associated with rhythmic oscillatory contractions of the muscle strips.4. Histamine caused an increased tone, with superimposed rhythmic fluctuations in tension. The electrical response consisted of depolarization, with rhythmic slow oscillations in potential (slow waves) which were synchronous with the fluctuations in tension.5. Acetylcholine produced smooth, tonic contractures of tracheal muscle strips, and caused simple depolarization of the membrane. No action potentials were recorded.6. In calcium-free solutions containing EGTA, the mechanical response to TEA was completely abolished; the response to histamine was greatly reduced; the response to acetylcholine was reduced to a lesser extent. All responses reverted to normal when normal concentrations of extracellular calcium were restored.7. Lanthanum added to the bathing solution abolished the contraction due to TEA even though the solution contained calcium. It reduced the histamine-induced contraction to 26 % of control, and reduced the acetylcholine-induced contraction to 58 % of control; extracellular calcium was present throughout.

The spontaneous electrical and mechanical activity of human bronchial smooth muscle: its modulation by drugs

“…Further, it is also conceivable that spontaneous contractions are artifactual due to the mediators released from the tissues by trauma during the preparative procedures. In accord with this, oscillations in membrane potential and subsequent spontaneous contractions have been observed in response to histamine (Kirkpatrick 1975) acetylcholine (Cameron & Kirkpatrick, 1977), 5-hydroxytryptamine (Coburn & Yamaguchi, 1977) or after prolonged treatment with indomethacin (Ito & Tajima, 1981b) in bovine or dog trachea. In the present experiments FPL 55712, indomethacin or atropine suppressed the slow waves and spontaneous contractions.…”

The spasmogenic action of potassium chloride in guinea‐pig trachealis

“…Direct evidence that KClpromoted spasm is potential-dependent comes from experiments where current pulses which return the membrane potential towards normal also suppress the spasm (Coburn & Yamaguchi, 1977). Dependence of KCl-induced spasm on extracellular Ca2+ has been demonstrated in the trachealis of the ox (Kirkpatrick, 1975) and the guinea-pig (Creese & Denborough, 1981). As yet, however, there has been no direct demonstration in trachealis of K+-promoted cellular influx of Ca2+* The present study comprises an analysis of the spasmogenic action of KCl in guinea-pig trachealis.…”

Actions of second messengers synthesized by various spasmogenic agents and their relation to mechanical responses in dog tracheal smooth muscle

“…For example, in the rabbit airway, the potassium (128 mm K)-and histamine (10pM)-induced contractions in the trachea are much smaller than the acetylcholine (ACh, 10 M)-induced contraction, but in the third branch of the right middle bronchial tree, these same three stimulants generate much the same amplitude of contraction and, moreover, the amplitude of the ACh-induced contraction is larger than that observed in the trachea (Fujiwara et al, 1988). In the guinea-pig, dog, bovine and rabbit tracheal and bronchial tissues, histamine produces contraction by stimulation of the Hl-receptor, though H2-receptors are also present (Chand & Eyre, 1975;Kirkpatrick, 1975;Kotlikoff et al, 1987). Ito & Tajima (1982) demonstrated that in the dog trachea, isoprenaline produces hyperpolarization of the membrane, reduces the resting tone and relaxes tissues precontracted by ACh.…”