- a substance released at certain sympathetic nerve endings: thought to be identical with adrenaline
C20: from sympath (etic) + -in
- A substance, such as norepinephrine, that diffuses into the circulation from the terminals of active sympathetic nerves and serves as a chemical mediator.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.