From
THE GOOD DRUG GUIDE..... Selegiline, also known as l-deprenyl, is an irreversible and (relatively) selective MAO-B inhibitor."
The enzyme monoamine oxidase has two main forms, type A and type B. They are coded by separate genes. MAO may be inhibited with agents that act reversibly or irreversibly; and selectively or unselectively. These categories are not absolute. MAO type-A preferentially deaminates serotonin and noradrenaline, and also non-selectively dopamine. Type B metabolises dopamine, phenylethylamine (the chocolate amphetamine) and various trace amines.
At dosages of below 10-15 mg daily, selegiline retains its selectivity for the type-B MAO iso-enzyme; but it is also a weak reversible inhibitor of the type-A MAO iso-enzyme. In contrast to unselective and irreversible MAO inhibitors such as tranylcypromine (Parnate) and phenelzine (Nardil), both of which strongly potentiate the catecholamine-releasing effect of tyramine, selegiline inhibits it. This ensures that selegiline does not induce the hypertensive "cheese effect".Selegiline has immune-system-boosting and anti-neurodegenerative effects. Its use increases the level of tyrosine hydroxylase, growth hormone, cerebral nitric oxide and the production of key interleukins. Selegiline offers protection against DNA damage and oxidative stress by hydroxyl and peroxyl radical trapping; and against excitotoxic damage from glutamate. In addition, selegiline stimulates the release of superoxide dismutase (SOD). SOD is a key enzyme which helps to quench damaging free-radicals.
Taken consistently in low doses, selegiline tends to extend the life-expectancy of rats by some 20%; enhances drive, libido and endurance; and independently improves cognitive performance in Alzheimer's patients and in some healthy normals. It is used successfully to treat canine cognitive dysfunction syndrome (CDS) in dogs.
Selegiline retards the metabolism not just of dopamine but also of phenylethylamine, a trace amine also found in chocolate and released when we're in love.
Selegiline protects the brain's dopamine cells from oxidative stress. The brain has only about 30-40 thousand dopaminergic neurons in all. We tend to lose perhaps 13% a decade in adult life. An eventual 70%-80% loss leads to the dopamine-deficiency disorder Parkinson's disease, frequently foreshadowed by depression.
Administered at low doses, selegiline is neuroprotective against possible damage to the serotonergic fine axon terminals caused by overconsumption of the popular drug MDMA (Ecstasy). Several competing theories exist to explain MDMA-induced neurotoxicity. One theory blames the deamination by MAO-B of excessive dopamine taken up by the membrane-bound transporter into the depleted serotonin terminals. This abnormal uptake follows MDMA-induced reversal of the serotonin reuptake pump. In the absence of MAO-B inhibition, deamination by MAO-B of excess dopamine taken up into the serotonergic axon terminals is liable to generate a glut of toxic free radicals. These highly reactive compounds cause membrane lipid peroxidation and consequent fine terminal degeneration. Selegiline prevents such serotonergic damage, in theory at any rate.On the other hand, co-administering unselective selegiline dosages or unselective irreversible MAOIs like tranylcypromine (Parnate) or phenelzine (Nardil) with MDMA is potentially lethal.
Taken at MAO-B-selective dosages, selegiline is typically less effective as a mood-brightener than other dopaminergics such as amineptine (Survector). Taken at unselective dosages of 20mg a day or more, selegiline is typically an effective, well-tolerated antidepressant. Selegiline at higher dosages may also be useful for "atypical" depressive symptoms of overeating, oversleeping, and sensitivity to rejection. An unselective dosage regimen calls for an MAOI diet.
Selegiline can be delivered via a transdermal patch. If the FDA permits, the patch will be marketed by Somerset Pharmaceuticals.
Either way, by the standards of posterity we are all probably glorified glue-sniffers. The impending Post-Darwinian Transition to an era paradise-engineering has dreadfully crude origins. But by today's standards, at least, selegiline is a potentially life-enriching agent...."
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