Alan J. Robinson
robin073 at maroon.tc.umn.edu
Fri Oct 20 07:37:32 EST 1995
On Thu, 19 Oct 1995 12:49:55 -0500,
Steve Rogers <srogers at delphi.beckman.uiuc.edu > wrote:
>Hi. Can anyone explain why certain brain structures (e.g. substantia
>nigra) contain the black pigment, melanin? Thanks in advance.
"Why" in biology is usually a tough question! Several years ago I
looked into this but only got so far. It has a bearing on skin
cancer, Parkinson's disease, and possibly some other diseases as well.
There are at least two forms of melanin - eumelanin and pheomelanin
- which are the basis of skin and hair color. Eumelanin is brown or
black, and pheomelanin is the pigment of red hair. Melanin is a
complex polymer derived from the amino acid tyrosine along part of the
same metabolic pathway for dopamine.
Several years ago I came across a paper from the Dermatology dept. at
a Swedish university which said that the substantia nigra pigment was
pheomelanin. Because many Scandinavians are red headed I wondered
if they were just getting a glimpse of the local color. I wrote to
the author but never received a reply.
The old wives tale about red heads having a fiery personality may or
may not have a biological basis, but it is well known that coat
color is associated with personality in several different animals -
cats, mice, foxes etc. My guess that this would have affect in humans
too, possibly through the pigments of the substantia nigra and the
locus ceruleus. Cloninger's brain model shows how personality and
susceptibility to a variety of disorders is based on differing
sensitivities of the DA, NE, and 5-HT pathways.
If anyone else has any more recent info, I would be very interested in
hearing about it too.
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