Inotrophic effects of the K(+) channel blocker TEA on dystrophic (mdx and dy/dy) mouse diaphragm.

K(+) channels regulate diaphragm resting membrane potential and action potential duration, and hence force. Certain blockers of these channels, e.g.

Effects on dystrophic (dy/dy) limb muscle of the K+ channel blocker tetraethylammonium.

K(+) channel blockers, such as tetraethylammonium (TEA) and 4-aminopyridine, increase force of normal skeletal muscle. To determine whether they also increase force of diseased muscle, effects of TEA were examined on limb muscles of dy/dy dystrophic mice in vitro. TEA significantly increased isometric twitch force of normal and dystrophic soleus muscle by 29.

Contractile properties of feline genioglossus, sternohyoid, and sternothyroid muscles.

Despite a wealth of information about the respiratory behavior of pharyngeal dilator muscles such as the genioglossus, sternohyoid, and sternothyroid muscles, little is known about their contractile and endurance properties. Strips of these muscles (as well as of the diaphragm) were surgically removed from anesthetized cats and studied in vitro at 37 degrees C. The isometric contraction times of the muscles were 38 +/- 1, 31 +/- 1, 28 +/- 2, and 35 +/- 1 ms for genioglossus, sternothyroid, sternohyoid, and diaphragm, respectively.

Contractile and endurance properties of geniohyoid and diaphragm muscles.

Despite the wealth of information about the neural control of pharyngeal dilator muscles, little is known about their intrinsic physiological properties. In the present study the in situ isometric contractility and endurance of a pharyngeal dilator, the geniohyoid muscle, were compared with properties of the diaphragm in 12 anesthetized artificially ventilated cats. The contraction time (means +/- SE) of the geniohyoid (27 +/- 2 ms) was shorter than that of the diaphragm (36 +/- 3 ms; P less than 0.

Effect of N-acetylcysteine on diaphragm fatigue.

It has recently been postulated that diaphragm fatigue may be due, at least in part, to a form of low-grade injury to subcellular organelles. Moreover, several studies have shown that thiol-containing compounds can protect cardiac and striated skeletal muscle organelles from the deleterious effects of a number of physiological stresses. The purpose of the present study was to determine whether pretreatment with N-acetylcysteine (NAC), a thiol-containing compound, would attenuate the rate of development of diaphragmatic fatigue.