Re: New Information on Mechanism of Action of Pergolide

Frances C.

Dear Dr. K, all this is too much for my feeble brain. Do we want to increase Dopamine? Would it be appropriate to feed L-theanine, a derivitive of green tea? I have been giving 1/2 teaspoon per day.

----- Original Message -----
From: Eleanor Kellon, VMD <drkellon@...>
Sent: Sun, 25 Oct 2020 13:44:20 -0400 (EDT)
Subject: [Special] [ECIR] New Information on Mechanism of Action of Pergolide

It has been established that PPID is caused by decreased production of dopamine by neurons in the hypothalamus which normally keep activity of the intermediate pituitary lobe in check. We talk about pergolide working because it is a dopamine agonist which stimulates D1 and D2 dopamine receptors, in essence substituting for the lost dopamine. A new study [October 2020] from Michigan State has proven there is more to it than that.

Research looking at the levels of dopamine in the pituitary of aged, young and treated (1 mg pergolide per 500 kg for 6 months) vs untreated PPID horses has found levels of dopamine in the pituitary are actually increased by pergolide.  The activity of tyrosine hydroxylate enzyme, which generates dopamine from tyrosine, was also increased in the hypothalamus.

Based on data from other species, the researchers hypothesized that pergolide  allowed dopamine to reaccumulate in dopamineric neurons by decreasing the demand for it - substituting for some of the natural dopamine. Activating the D1 and D2 receptors may also provide positive feedback to the remaining neurons, resulting in increased tyrosine hydroxylase activity. 
EC Owner 2001

- Frances C.
December 2017, Washington & California
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