In article <srogers-1910951249550001 at ara1.life.uiuc.edu> srogers at delphi.beckman.uiuc.edu (Steve Rogers) writes:
>From: srogers at delphi.beckman.uiuc.edu (Steve Rogers)
>Subject: Brain pigment
>Date: Thu, 19 Oct 1995 12:49:55 -0500
>Hi. Can anyone explain why certain brain structures (e.g. substantia
>nigra) contain the black pigment, melanin? Thanks in advance.
>****************************************************
>Steve Rogers
>Dept. of Cell & Structural Biology and the
>Beckman Institute - Optical Visualization Facility
>Univ. of Illinois @ C-U
>srogers at delphi.beckman.uiuc.edu>****************************************************
See, ( he says modestly ) P. Proctor, Free Radicals and Human Disease, in
Crc Handbook of Free Radicals and Anbtioxidants, vol 1, p211 ( l989 ).
Basically, there are several possible explanations for the existance of
Neuromelanin: It's not just a pigment of your imagination :-).
1) It's just junk stuff with builds up.
2) It has a protective and or modulator function against free radicals and
excited-state species. These are produced all over the place and several of
them ( e.g. superoxide and nitric oxide ) are almost certainly
neurotransmitters. E.g., melanin has superoxide dismutase activity.. Such
active species are generally though to play a key role in pathogenesis.
3) It has something to do with nerve cell function. The stuff has some rather
exotic semiconductor propeties. E.G., it's an amorphous semiconductor
threshold switch as well as an electret. I can come up with all sorts of
neat models on how it may modulate axonal depolarization.
4) All of the above.
Also, there are lots of pigmented areas in the brain, not just the Sub.
Nigra and the Locus ceruleus. Further, autooxidation-catalyzing melanin
binding agents ( e.g., in manganism, the Lesch-Nyhan syndrome, or Wilson's
disease ) tend to be associated with psychosis and dyskinetic symptoms. As
well as deafness.
Also, melanin is the most potent sound-absorbing agent known. Sure
enough, it is present in the inner ear. Depigmenting syndromes ( E.G.
Waardenburg's syndrome as well as blue-eyed white cats ) tend to be
associated with Deafness.
Peter H. Proctor, PhD, MD
