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Michael, I don't know about the eyes and dopamine but probably Dr. Jaquie Winterkorn does. She just posted after al long absence on the list. I'm glad to see her back. You do need to watch out for certain PD meds especially the anticholenergics which can increase intraoccular pressure through another mechanism. Regarding the location of the dopamine outside of the substantia nigra many other areas of the brain contain dopamine which do not affect movement. For instance in my field- psychiatry hallucinations are stopped by dopamine blockers- which can cause a PD like syndrome. Also the gut seems to produce a lot of dopamine as Hans has already said. I found the following abstract: Abstract Substantial production of dopamine in the human gastrointestinal tract. ---------------------------------------------------------------------------- ---- Authors: Eisenhofer G , Aneman A , Friberg P , Hooper D , F~andriks L , Lonroth H , Hunyady B , Mezey E Clinical Neuroscience Branch, National Institute of Neurological Disorders and Stroke, National Institute of Health, Bethesda, Maryland 20892-1424, USA. [log in to unmask] J Clin Endocrinol Metab 1997 Nov;82(11):3864-71 Article Number: UI98025005 Abstract: Considerable urinary excretion of dopamine metabolites indicates that large amounts of dopamine are produced in unknown locations of the body. This study assessed the contribution of mesenteric organs (gastrointestinal tract, spleen, and pancreas) to the total body production of dopamine in humans and examined the presence of the rate-limiting enzyme for dopamine synthesis, tyrosine hydroxylase, in gastrointestinal tissues. Blood sampled from an artery and portal and hepatic veins in eight subjects and from arterial and renal venous sites in other subjects was analyzed for plasma concentrations of dopamine and its metabolites. The activity and distribution of tyrosine hydroxylase was also examined in tissue samples from the stomach and duodenum. Higher concentrations of dopamine and its metabolites in portal venous than arterial plasma indicated substantial production of dopamine by mesenteric organs (12.0 nmol/min) amounting to 42-46% of the renal removal of circulating dopamine metabolites. Tissue samples showed immunoreactive tyrosine hydroxylase in nonneuronal cell bodies and detectable levels of tyrosine hydroxylase in nonneuronal cell bodies and detectable levels of tyrosine hydroxylase enzyme activity. The results show that mesenteric organs produce close to half of the dopamine formed in the body, most of which is unlikely to be derived from sympathetic nerves but may reflect production in a novel nonneuronal dopaminergic system. " As you can see the amount from any one place would be dwarfed by the total amount of dopamine produced- which is a problem in psychiatric research as well. Charlie ----- Original Message ----- From: Michael Kamensky <[log in to unmask]> To: <[log in to unmask]> Sent: Tuesday, November 30, 1999 9:38 AM Subject: Re: Stress and PD > > From: "Charles T. Meyer, M.D." <[log in to unmask]> > > > dopamine metabolites are made in the body in different areas than the > > substantia nigra and therefore the metabolites I believe are unable to be > > separated from the metabolites of dopamine from other sources. > > > So what other areas make dopamine? I've heard that the eyes make trace > amounts but haven't heard of other areas. > > I'm personally curious to learn if dopamine loss from the eyes impacts at > all on glaucoma. I'm at an increased risk of glaucoma because my intraocular > fluid pressures were right at the high end of normal (19-21 milligrams [or > micrograms, I can never remember which] of mercury) on pressure tests the > last two years, plus I'm very nearsighted. If my pressure readings get into > the mid-20's I'd have to take eyedrops every day to lower the pressures and > prevent the onset of the disease.