K+-induced alterations in airway muscle responsiveness to electrical field stimulation
We investigated possible pre- and postsynaptic effects of K+-induced depolarization on ferret tracheal smooth muscle (TSM) responsiveness to cholinergic stimulation. To assess electromechanical activity, cell membrane potential (Em) and tension (Tm) were simultaneously recorded in buffer containing 6, 12, 18, or 24 mM K+ before and after electrical field stimulation (EFS) or exogenous acetylcholine (ACh). In 6 mM K+, Em was -58.1 +/- 1.0 mV (mean +/- SE). In 12 mM K+, Em was depolarized to -52.3 +/- 0.9 mV, basal Tm did not change, and both excitatory junctional potentials and contractile responses to EFS at short stimulus duration were larger than in 6 mM K+. No such potentiation occurred at a higher K+, although resting Em and Tm increased progressively above 12 mM K+. The sensitivity of ferret TSM to exogenous ACh appeared unaffected by K+. To determine whether the hyperresponsiveness in 12 mM K+ was due, in part, to augmented ACh release from intramural airway nerves, experiments were done using TSM preparations incubated with (3H)choline to measure (3H)ACh release at rest and during EFS. Although resting (3H)ACh release increased progressively in higher K+, release evoked by EFS was maximal in 12 mM K+ and declined in higher concentrations. We conclude that small elevations in the extracellular K+ concentration augment responsiveness of the airways, by increasing the release of ACh both at rest and during EFS from intramural cholinergic nerve terminals. Larger increases in K+ appear to be inhibitory, possibly due to voltage-dependent effects that occur both pre- and postsynaptically.
- Research Organization:
- Univ. of Cincinnati School of Medicine, OH
- OSTI ID:
- 5141765
- Journal Information:
- J. Appl. Physiol.; (United States), Vol. 1
- Country of Publication:
- United States
- Language:
- English
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59 BASIC BIOLOGICAL SCIENCES
CELL MEMBRANES
ELECTRIC POTENTIAL
ELECTROMAGNETIC FIELDS
BIOLOGICAL EFFECTS
TRACHEA
ELECTROPHYSIOLOGY
ACETYLCHOLINE
IN VITRO
MUSCLES
POTASSIUM
TRITIUM COMPOUNDS
ALKALI METALS
AMINES
AMMONIUM COMPOUNDS
AUTONOMIC NERVOUS SYSTEM AGENTS
CELL CONSTITUENTS
DRUGS
ELEMENTS
ESTERS
LABELLED COMPOUNDS
MEMBRANES
METALS
NEUROREGULATORS
ORGANIC COMPOUNDS
PARASYMPATHOMIMETICS
PHYSIOLOGY
QUATERNARY COMPOUNDS
RESPIRATORY SYSTEM
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