 |
 |
There's a bit of confusion regarding the inhibition reaction you're talking about. The following is the complete reaction to produce dopamine: tyrosine (with the help of the enzyme tyrosine hydroxylase) produces L-dopa, L-dopa (with the help of the enzyme aromatic amino acid decarboxylase) then produces dopamine. This all typically takes place in a region of the brain called the substantia nigra. The dopamine in the substantia nigra then has an inhibitory effect on another region of the brain called the putamen. I won't bother with the rest of the pathway, ( if someone is interested, I will soon be posting a diagram at www.pallidotomy.com) but the important point to understand is that the lack of dopamine no longer inhibits the Putamen, thereby causing the pathway much further down the line to inhibit the Thalamus (which is the brain's motor output unit). -----Original Message----- From: Joe Bruman <[log in to unmask]> To: Multiple recipients of list PARKINSN <[log in to unmask]> Date: Monday, August 25, 1997 3:39 PM Subject: Re: Biochemistry question on dopamine regulation >Baldwin Robertson wrote: >> >> My question is: How is the level of dopamine regulated? >> Does dopamine inhibit tyrosine hydroxylase or does it inhibit the >> expression of the enzyme? What is the specific mechanism for >> the inhibition reaction? That is, what are the specific reactions >> that accomplish the regulation? > >Not a biochemist, and I know nothing of the molecular reactions you >describe; but I suspect the regulation is done by the neurons that >express dopamine for each specific synaptic impulse. I think I read >somewhere that excessive dopamine level outside the cell not only is >the cause of dyskinesia, but also somehow triggers apoptosis; and that >is why the crude therapy of adding dopamine by eating levodopa is >viewed with concern by some. Cheers, >Joe > >J. R. Bruman (818) 789-3694 >3527 Cody Road >Sherman Oaks, CA 91403-5013 >