Main Entry: sym·pa·thin Pronunciation: 'sim-p&-th&n Function: noun : a substance (as norepinephrine) that is secreted by sympatheticnerve endings and acts as a chemical mediator
sympathin sym·pa·thin (sĭm'pə-thĭn) n. A substance, such as norepinephrine, that diffuses into the circulation from the terminals of active sympathetic nerves and serves as a chemical mediator.
