Obviously those questions can only be answered by each company's internal personnel and laboratory test results.
A better questions is: Why does two S1R agonist drugs (such as A2-73 and Fluvoxamine) come out with two completely opposite results on, say, the quality of sleep?
A2-73 showed excellent results in increasing REM sleep while Fluvoxamine causes insomnia.
Is it because each S1R agonist drug binds to the S1R differently...and therefore, the results of each drug's binding causes a different outcome?
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You can't equate Pridopidine's results (or any other sigma-1 receptor agonist drug) with A2-73 because each S1-R agonist drug binds to the Sigma-1 receptor in a different way.
Below is a partial list of other sigma-1 receptor agonist drugs:
PRE-084
A2-73
Donepezil
Fluvoxamine
Citalopram
Amitriptyline
L-687,384
SA-4503
Dextromethorphan
Dimethyltryptamine
Each one of these Sigma-1 receptor agonist drugs binds to the sigma-1 receptor differently...and, for the most part, causes a different outcome.
A very popular drug listed above is Fluvoxamine. Below is a partial list of its side effects:
Loss of appetite
Agitation
Nervousness
Anxiety
Insomnia
As you know, participants in almost every study using A2-73 has reported sleeping better...which is the opposite of insomnia.
As I stated before, Anavex has several patents on their drugs because they have figured out the best way to bind to the sigma-1 receptor. (In my opinion, of course)
To quote from wikipedia:
"Also, sigma-1 receptors have been shown to appear in galactoceramide enriched domains at the endoplasmic reticulum of mature oligodendrocytes.[24] The wide scope and effect of ligand binding on sigma-1 receptors has led some to believe that sigma-1 receptors are intracellular signal transduction amplifiers.[14]"
Bottom line: Not all sigma-1 receptor drugs are alike...and therefore their results should not be compared equally to each other.
abew4me "abe"