Terribly sorry; I omitted one more person's reply in the summary I just sent.
Here it is.
From: Brendan O'Brien <creator at u.washington.edu>
Sender: creator at carson.u.washington.edu
To: hucka at engin.umich.edu
Subject: centrifugal pathways...
Date: Fri, 16 Jul 1993 17:26:42 -0700 (PDT)
Recently I did a paper on modulation of gap junctions by dopamine in fish
retina. As it turns out DA is released into the retina via the terminals
of cells found in the "isthmo-optic" nucleus (I think that's right, you
might check it though. It was a Dowling paper in the mid-80's) in the
brainstem. When the fish eyes are dark-adapted it turns out that
horizontal cells across the retina are electrically coupled via the gap
junctions. When the retinae are stimulated, however, DA is released into
the retina which causes uncoupling of the gap junctions. This is
supposedly to modify the sensitivity of the retina over large changes in
ambient light. I am not a retinal researcher, but I believe there has
been speculation that the retinopetal fibers in fish and amphibians are
homologous with dopaminergic interplexiform cells in the primate retina.
(homologous in this sense meaning having the same function). I don't
know of anyone ever showing retinopetal fibers in primates but I'm not
certain if anyone has _really_ looked for them either.
Feel free to write me if you need more info, or if this isn't quite clear
creator at u.washington.edu
Mike Hucka | Internet: hucka at engin.umich.edu
University of Michigan AI Lab | 1101 Beal Ave., Ann Arbor, MI 48109-2110