Posted by SLS on April 26, 2009, at 5:49:56
In reply to purpose of MAO-B, posted by iforgotmypassword on April 26, 2009, at 3:02:43
> i know MAO-B apparently has the effect of metabolizing dopamine to some extent. in whichever way it does this, wherever in the brain, and to what extent, does this have a use? is there anything else that MAO does that has a use?
>
> it may be that MAO-B inhibition may be unlikely to hurt people, it may be the basis of the one benefit of smoking. (referring to the research implying that it seems to delay idiopathic parkinsonian neurodegeneration.) smoking however, i don't believe wipes out MAO-B, so even if MAO-B inhibition was one of the safe effects of tobacco smoking, it may not indicate that total MAO-B inhibition over long periods in healthy individuals is without risk, if there is some use for this enzyme...
>
> or, does MAO-B exist almost as if by accident, as an unavoidable product of MAO-A production?
As usual, you ask great questions that I cannot answer. I don't know the evolutionary history of the two isoenzymes, so it is difficult to guess which one acted as the primary enzyme of deamination. I know lobsters use serotonin, so they must have some MAO-A to regulate their metabolism.I believe that it is MAO-A that is the more relevant pharmacological target in the treatment of depression and anxiety disorders. It is interesting to note that the same person who does not respond robustly to the selegiline oral preparation does respond so when using the patch delivery system. Even at the lowest dosage, the patch system delivers enough selegiline for it to lose its selectivity for MAO-B and is thus inhibiting MAO-A as well. MAO-A does deaminate dopamine as well as norepinephrine and serotonin. We must take regional distribution of the two enzymes into account to really understand their function or emergence evolutionarily.
You should research at what point in the evolutionary development of the brain did the different isoenzymes emerge. Even looking at the more primative structures of the brain for enzyme distribution would be interesting.
- Scott
poster:SLS
thread:892825
URL: http://www.dr-bob.org/babble/neuro/20090129/msgs/892835.html