I'm curious; Are the neurotoxic effects of amphetamine solely related to oxidative stress? Don't amphetamines work mainly by reuptake inhibition rather than DAT reversal, when used at perscribed dosages? In that case I would assume that they would have a similar mechanism as methylphenidate and therefore little worry of toxic effects. Hmm? I must be wrong, but in case I'm not, then the big question would therefore be how much amphetamine is necessary to cross from monoamine reuptake to release.
As far as my understanding goes stimulant neurotoxicity is indeed pretty much is limited to oxidative stress; the methylated-amphetamine derivatives like MD(M)A and Methamphetamine are much more lipophilic and are absorbed by the body at a greater percentage and at a higher rate. someone mentioned earlier in this thread that the onset of oral d-methamp is not markedly different from that of d-amp and its sister-salts; I've found this to be completely untrue - Desoxyn, which I am prescribed, is the *only* oral IR (or XR, for that matter) tablet in my life that I've swallowed and -
despite a full belly or not - felt within 5-8 minutes. No variation.
So anyway, its rapid absorption, coupled with the fact that the methylated amphetamines are the most potent serotonergic and dopaminergic stimulants, creates the perfect environment for oxidative stress. The high level of serotonin agonism contributes to the release of things like peroxide, hydroxide, some others that are eluding me at the moment - and these oxidative compounds are highly damaging to nerve cells.
Normally, our bodies can deal with the impact of oxidative stress because we naturally produce these compounds on a day-to-day basis; but when there is a supra-efflux of serotonin, their production and thus presence augments greatly and then the marked increase in DA agonism increases body temperature, impairing the nerve cells' ability to repel the deleterious effects of the oxidative compounds. This, in turn and with time, leads to nerve cell death ("apoptosis," it's referred to).
So, to sum it up, the more 5HT and DA agonism a stimulant produces, the more dangerous environment the combination creates for the well-being of our precious neurons. If continuous usage is still going to occur, you should really invest in some anti-oxidants - there was a wonderful thread from a bit back where people were chiming in all sorts of wonderful vitamins, minerals and oils that act as great anti-oxidants that can assist in preventing (or at least inhibiting) the progression of stimulant-bound neurotoxicity. A few that I remember were Vitamin C, Vitamin E, selenium, inosine, alphia-lipoic acid, N-acetyl-cysteine (sp?), and idebenone. Some of these I take already, but being that I'm only two months into my daily consumption of methamphetamine HCl tablets (4x 5mg tab/day = 20mg/day), I haven't quite stock-piled a good selection yet.
Don't amphetamines work mainly by reuptake inhibition rather than DAT reversal, when used at perscribed dosages?
I believe this is slightly misinformed - or, rather, DA reuptake inhibition is but a symptom of the pharmacology of amphetamines. Take a quote from
THISwebsite, for instance: "
Amphetamines’ 3 main effects on dopamine transport are depletion of vesicular dopamine (DA), reversal of DAT (efflux of DA into synaptic cleft), and DA uptake inhibition (Caron et al, 1998).. Methylphenidate is a DATI (dopamine transporter inhibitor), whilst amphetamine and its derivatives and analogues work by DAT reversal. Interestingly enough, I did some research a little while back and discovered that methylphenidate, as a DATI, can actually help
prevent amphetamine-induced DA deficiencies! How 'bout that? Solving your amphetamine problems with Ritalin, what a world. But, see for yourself, the following is from a file I wrote up myself with links just so I could wrap my mind around the idea; the links and/or citations following the verification statements, as they are, ought still be valid:
A. Premise:
1. DAT-Inhibitors (DATI's) protect against METH-induced DA deficits
and…
2. Methylphenidate is a DATI
therefore...
3. Methylphenidate should protect against METH-induced DA deficits
----------------------------------------------------------------------------------------------
B. Verification:
1. DAT-Inhibitors (DATI's) protect against METH-induced DA deficits
"Methamphetamine Toxicity and Messengers of Death." Irina N. Krasnova, Jean Lud Cadet. Molecular Neuropsychiatry Research Branch, Intramural Research Program, NIDA/NIH/DHHS, 251 Bayview Boulevard, Baltimore, MD 21224, USA
Accepted 16 March 2009
Available online 25 March 2009
http://www.toxicology.tcu.edu.tw/files/class_0981/神經毒理學特論/980923.pdf
2. Methylphenidate is a DATI
"Relationship between blockade of dopamine transporters by oral methylphenidate and the increases in extracellular dopamine: therapeutic implications."
http://www.ncbi.nlm.nih.gov/pubmed/11793423
3. Methylphenidate should protect against METH-induced DA deficits
"Methylphenidate Alters Vesicular Monoamine Transport and Prevents Methamphetamine-Induced Dopaminergic Deficits." Veronica Sandoval, Evan L. Riddle, Glen R. Hanson, and Annette E. Fleckenstein. Department of Pharmacology and Toxicology, University of Utah, Salt Lake City, Utah. Received October 3, 2002; accepted December 4, 2002.
And the last bit from the document I typed up, I apparently didn't deem it necessary to validate this with a reference, but I remember happening across the information (pertinent or impertinent to this discussion, you make the call) as I was doing more in-depth research on the aforementioned subject:
Methamphetamine is a DA reuptake inhibitor.
>Methamphetamine decreases reabsorption of DA by synaptic vesicles, resulting in more DA in the synapse and less DA in the vesicles.
>METH causes DAT (dopamine transporter) upregulation (increase of a cellular component)
Therefore, because methylphenidate works against the DA transporter - and methamphetamine's neurotoxicity is caused in part by its ability to promote the activity of said transporter - methylphenidate fights the neurotoxicity caused by meth on the battleground occupied by these DAT's.
Anyway, I hope what I've said makes sense; sorry to resurrect such an old thread but I found myself doing a bit of investigative research for my own purposes and thought I'd chime in.
~ vaya