- L-glutamic acid, a neurotrophic factor for maintenance of acetylcholinesterase and butyrylcholinesterase in the preganglionically denervated superior cervical ganglion of the cat. Koelle, G.B., Sanville, U.J., Thampi, N.S., Wall, S.J. Proc. Natl. Acad. Sci. U.S.A. (1986)