For most of us, by the time Parkinson's is diagnosed, something like 80 percent of the dopamine producing neurons have already perished. Likewise, for most of us, in retrospect we realize that Parkinson's symptoms had been building for some time prior to diagnosis, typically for years.
According to the current medical understanding, for which there is good evidence, Parkinson's is caused by accumulated aggregates of alpha synuclein that neurons are unable to dispose of.
In the title, "pretreatment" refers to the practice, in animal studies, of pretreating the animal with a test substance and then subsequently, or simultaneously, applying a toxicant that causes a Parkinson's like condition. In this case, if the test succeeds, that means the substance has prevented the aggregation of clumps of alpha synuclein. This has little to do with treating actual Parkinson's. That requires the dissolution of formed clumps of alpha synuclein. To test this, the animal must be treated with the toxicant first, time allowed for the alpha synuclein aggregates to form, and then treated with the test substance.
It is very frustrating to find that most animal studies are of pretreatment only. Based on the foregoing, this is not evidence of efficacy in treating Parkinson's.
Now let us consider that these animal trials typically have several arms, consisting of some or all of the following:
• The control arm of toxicant only
• Test substance plus toxicant, possibly more than one arm with different dosages, with simultaneous application or pretreatment with test substance
• Negative control of toxicant vehicle only
• Test substance only
With some or all of these arms going already, the cost of adding an additional arm of test substance applied after toxicant, rather than before, is insignificant. Why do investigators not do that? Maybe they do!
Let us suppose that they do and the posttreatment arm fails but the pretreatment arm succeeds. If this happens and they disclose the failure of the posttreatment arm, no one is going to be very interested in publishing a study with success in the pretreatment arm but failure in the posttreatment arm. What to do? Deep six the failed posttreatment arm and publish the success story. I do not know that this is happening, but I wonder.
These kinds of papers are mostly published by academic researchers. Before someone accuses me of hating on researchers, I do not. The academic model is "publish or perish". The pressure is intense as is the competition to get funding. I know of someone involved in academic research, not medical, and he has been in an ongoing state of stress for years. So if this is going on I would blame the system rather than the researchers.
Update – case in point of why pretreatment versus posttreatment matters. A lot: jstage.jst.go.jp/article/dd...
"Pre-treatment with eugenol reversed motor dysfunction caused by MPTP administration while post-treatment with eugenol at a high dose aggravated the symptoms of akinesia associated with MPTP administration."[Emphasis added]
Update – Investigators serious about treating Parkinson's they make sure the test animal has Parkinson's before applying treatment
Cases in point:
Inhibikase Therapeutics C-Abl inhibitor IkT-148009 science.org/doi/10.1126/sci...
"PD, IkT-148009 suppressed c-Abl activation to baseline and substantially protected dopaminergic neurons from degeneration when administered therapeutically by once daily oral gavage beginning 4 weeks after disease initiation. Recovery of motor function in PD mice occurred within 8 weeks of initiating treatment concomitantly with a reduction in α-synuclein pathology in the mouse brain." [emphasis added]
Inhibikase ran a phase 2 trial, which unfortunately failed. It was poorly designed - far too short to demonstrate efficacy.
Cinnamon
In this study: Reduction of Lewy Body Pathology by Oral Cinnamon link.springer.com/article/1...
Investigators used 10-month-old A53T mice. These mice are genetically modified to produce defective human Alpha synuclein with the A53T mutation. Regarding these mice: alzforum.org/research-model...
"Moreover, around 10 months of age they begin to develop severe motor impairments (Lee et al., 2002). Early signs of impairment include wobbling and posturing."
My report on Cinnamon here: healthunlocked.com/cure-par...