Studies of cholinesterase were begun about seventeen years ago by Loewi1 and his co-workers. These authors proved that the effects of stimulation of the vegetative nervous system are transmitted to the effector organs through humoral channels. Loewi demonstrated that stimulation of the cardiac branch of the vagus nerve gives rise to a vagotropic substance, which likewise is liberated by stimulation within the sympathetic and parasympathetic nervous systems. The liberated substance in all probability represents acetylcholine. Loewi and Navratil observed that aqueous extract of frog heart destroyed the so-called vagus substance, which was found to be indistinguishable from acetylcholine. The destructive agent was thermolabile and possessed other characteristics of an enzyme, and hence it was considered an acetylcholine esterase. Engelhart showed on isolated frog heart that physiologic excitation of the oculomotor nerve causes acetylcholine to appear in the aqueous. Dale would call the substances cholinergic, disregarding the anatomic origin in
RADOS A. BLOOD CHOLINESTERASE VALUES OF PATIENTS WITH GLAUCOMA. Arch Ophthalmol. 1943;30(3):371–375. doi:10.1001/archopht.1943.00880210095010
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