THE EFFECT OF ATROPINE UPON SKELETAL MUSCLE IN THE GOAT WITH MYOTONIA CONGENITA

¹ Neurology Branch, Clinical Research Division, U. S. Army Chemical Warfare Laboratories, Army Chemical Center, Maryland

Intraarterial injections of atropine (0.1 mg to 1.0 mg/kg) promptly reduce the isometric twitch tension of the striated muscle of the goat with myotonia congenita; rapid recovery follows.

The effects of instraarterial injections of atropine (0.5 mg and 1.0 mg/kg) upon brief tetanus of the skeletal muscle of the myotonic goat are primarily those of temporarily improving the speed and completeness of rehaxation, by reducing the initial frequency and duration of the asynchronous volley of muscle action potentials.

In the unanesthetized goat with myotonia congenita, functional benefit from intravenous injections of atropine (0.1 mg and 1.0 mg/kg) could not be proven.

The susceptibility of myotonic goat muscle to atropine does not differ from that of normal goat muscle, but the sensitivity of myotonic muscle to injecetd acetylcholine and to anticholinesterase agents is greater than that of normal goat muscle.

The cholinesterase levels of normal and of myotonic goat muscle do not differ significantly.

These observations do not support explanation of the symptoms in myotonia congenita by either lowered cholinesterase activity or some other direct abnormality of the chemical mediator system in responses to nerve stimlation.