Page 183 - The Miracle of Hormones

Communication in Nerve Cells

The Planning and Timing in the Messenger Molecules

The density of the chemical messengers and the time they remain in
the synapse cavity directly influence the communication between the
two neurons. Different mechanisms exist for each chemical messenger.

Some messengers disperse after they deliver their messages. Others are
broken down by special enzymes after they have performed their func-
tions. For example, the messenger molecule called "acetylcholine" is con-
verted by a special enzyme into choline and acetate.
There is yet another marvelous mechanism in the nerve cells: The
messengers that transmit a message to the receptor cell are gathered back
again into the transmitter cell and are stored there to be used in a subse-
quent message. This operation is performed by a few special molecules.
The activity of the dopamine and serotonin molecules is regulated in this
way. If we consider how difficult it is to recycle products, we can better
understand the effectiveness of this mechanism in the nerve cells.
Every phase of chemical communication occurs within an incredi-
bly delicate balance. Every messenger molecule used in every communi-
cation, and every protein and enzyme that performs a function in the

various stages, must be designed. The number of messenger molecules
that will be stored, how long the receiver cell will be stimulated, the time
for disintegration or reassembly are a part of the necessary communica-
tion balances. Moreover, an important number of details relating to com-
munication balances is still unknown.
Parkinson's disease is a condition that destroys muscle coordina-
tion, makes movement difficult, and causes tremors. The cause of this
disease is the destruction of the balance between the messenger molecu-
les dopamine and acetylcholine. When some nerve cells in the brain pro-
duce less dopamine than is required, the result is the loss of muscle
control. This fact came to light only recently (Professor Arvid Carlsson
was awarded by the Nobel Prize for his discovery).

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