It was shown by von Brücke in 19381 that corneal epithelium contains a remarkably high concentration of acetylcholine (ACh) and that corneal stroma contains almost none. The concentration in the corneal epithelium of rabbits appeared to be in the order of magnitude of 100γ to 200γ/gram and that in the stroma, of about 0.6γ/gram.
The high concentration of ACh in the epithelium is very intriguing and may be maintained by either one of the following mechanisms: ACh may originate in the perikaryon of the fifth nerve, flow down in the axon, and pile up in the nerve terminal, or it may be locally synthesized in the cornea either in the nerve terminals or in the epithelial cells. In all these events the presence of a choline acetylating system (ChAc), in the epithelium, is to be expected, although a high enzyme concentration is more suggestive of "local" synthesis of ACh