>
> just some really knowledgable answers would be something - but evidently the
> opthamologists with substantial answers are fewer and farther between than
> the
> neuro's .....so we continue to find the things we can do and keep
> searching.....
>                                              Marie

The following abstract/review may give an indication as to the  "state of the
art"
concerning the function of dopamine in the eye-- is still vague.

Dopamine functions outside the brain are interesting.

Delete if you don't like wading through the following.
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Fundam Clin Pharmacol 1993;7(8):449-63

Dopaminergic modulation of visual sensitivity in man.

Masson G, Mestre D, Blin O

UA CNRS 1166 "Cognition & Mouvement", Universite Aix-Marseille II, France.

A large body of experimental evidence supports the hypothesis that dopamine
is a functional neuromodulator at many levels of the visual system.
Intrinsic dopaminergic neurons were characterized in most mammalian retina,
including man. These neurons give rise to a dendritic plexus covering the
retina. Thus, dopamine seems to be involved in the organization of the
ganglion cell and the bipolar cell receptive fields and modulates
physiological activity of photoreceptors, both processes which underlie
sensitivity and spatial selectivity of visual processing in the early stage
of the visual system. Moreover, few data are now available concerning the
functional significance of dopaminergic modulation of visual sensitivity in
man. Parkinson's disease is a specific disorder of central dopaminergic
systems. Abnormalities in the pattern-evoked potentials and
electroretinogram have been found in parkinsonian patients. Contrast
sensitivity, a useful tool for measuring visual spatio-temporal sensitivity
in man, has also been shown to be modified due to this affection. Dynamic
contrast sensitivity is primarily decreased in these patients,
distinguishing them from the normal aging process. Because these
modifications in shape of the contrast sensitivity function are reversed by
L-Dopa, and that neuroleptic administration could reproduce them in
schizophrenia patients, it was suggested that dopamine might tune the
contrast sensitivity function in man. We have recently shown that
subcutaneous apomorphine induces changes in contrast sensitivity in healthy
volunteers, which preferentially affect motion sensitivity. These
dopaminergic sensitive modifications in the shape of the contrast
sensitivity function might reflect a change in the range of sensitivity of
the visual system, both in dynamic and spatial properties. This could be
explained by a modification in the spatial and dynamic properties of the
ganglion cell responses in the retina. Moreover, we suggest both from our
results and from the review of the literature that human psychophysical data
confirm the hypothesis that dopamine may be involved in light retinal
adaptation, as light-induced and dopamine-induced modifications in the shape
in the contrast sensitivity function are quite similar.

Publication Types:

   * Review
   * Review, tutorial

PMID: 8294083, UI: 94124093
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                             Ray Strand
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...on the edge  of the prairie abyss ......................