Noun
A
catecholamine
hormone
and
neurotransmitter
;
as
a
hormone
,
secreted
by
the
adrenal
gland
in
response
to
stress
(
when
it
stimulates
the
autonomic
nervous
system
);
as
a
neurotransmitter
,
synthesized
from
norepinephrine
.
It
is
also
used
as
a
medication
.