The action of tetraethylammonium (TEA) on the rat diaphragm.

Abstract

Summary. 1. The action of tetraethylammonium (TEA) on the contractions of the isolated phrenic nerve diaphragm preparation from kittens has been investigated and compared with the action on other mammalian nerve-muscle preparations. 2. TEA in a concentration of 1 mM increased the height of isotonically recorded muscle twitches about 20 to 30% after stimulation of the muscle both indirectly and directly after full curarization. No change in the muscle action potentials was observed after addition of TEA to a concentration of 1 mM. The β-hydroxy-derivative of TEA had a similar but slightly less potent effect on the twitch height. 3. Addition of TEA to the bath fluid of the kitten diaphragm increased the isometric peak twitch tension and the time from stimulus to twitch peak without significant increase in the rate of rise of tension. The maximal tetanic tension was unaltered or lowered after addition of TEA. These changes can be accounted for by a prolongation of the active state of the muscle by TEA. 4. TEA in a concentration of 1 mM did not significantly change the twitch height of isolated diaphragm preparations from rats, young guinea pigs or young rabbits. Injection of TEA (5 mg/kg) in rabbits and cats did not increase the twitch height of the hind limb muscles. The respiratory excursions of rabbits were unchanged while those of the cat increased markedly after this dose of TEA. It is concluded that the diaphragm muscle of kittens and of cats is more sensitive to TEA than the other mammalian muscles investigated.