Also found in: Dictionary, Encyclopedia.
The substance diffusing into circulation from sympathetic nerve terminals when they are active. The term was introduced by WB Cannon, who thought that this substance differed from the mediator produced by the nerve ending (now known to be incorrect); the mediator itself (norepinephrine) diffuses into circulation.
Synonym(s): sympathetic hormone
sympathinAn older, nonspecific term for:
(1) A catecholamine, in particular norepinephrine;
(2) A sympathetic neurotransmitter.
Sympathin is not used in the working medical parlance.
a neurohormonal mediator of nerve impulses at sympathetic nerve synapses; the term is used only when the nature of the mediator is unknown.