CHEMISTRY OF THE BRAIN: MOLECULES, MOOD, AND MENTAL ILLNESS - Chemistry: Notable Research and Discoveries - page 100

in physiology or medicine for their research on the
brain. Although Golgi continues to argue that neu-
rons may be physically connected, Cajal correctly
states that most neurons are separate cells.

British researchers Thomas Elliot (1877-1961) and
John Langley (1852-1925) develop the idea of a re-
ceptor—a molecule to which chemicals bind and
exert effects on a cell.

191 The U.S. government passes the Harrison Act,

which regulates narcotic substances.

191 German-born physician Otto Loewi (1873-1961)

performs an experiment with frogs in which he
stimulates a frog's vagus nerve, a branch of which
influences heart rate. When Loewi transfers the
fluid surrounding this vagus nerve onto the iso-
lated heart of another frog, its rate is affected in the
same way. This experiment suggests that the vagus
nerve releases some substance that acts on its tar-
get organs.

19 German physiologist Wilhelm Feldberg (1900-93)

and British researcher Sir John Gaddum (1900-65)
show that chemical transmission takes place, dem-
onstrating that certain nerves release the chemical
acetylcholine.

19 Maurice M. Rapport, Arda Alden Green, and Ir-

vine H. Page of the Cleveland Clinic Foundation
in Ohio isolate and name the chemical serotonin,
which they discover in the blood.

190s The monoamine hypothesis of depression develops

from the finding that drugs reducing monoamine
neurotransmission cause depression. Monoamines
include serotonin, norepinephrine, and dopamine.