Posted by Tomatheus on November 29, 2005, at 18:32:12
In reply to New drug company to pursue RIMAs in U.S., posted by Tomatheus on November 29, 2005, at 17:58:14
Since I posted this press release, I feel obligated to point out a factual error I found in it.
Sentence from the press release:
"Unlike two major
classes of existing antidepressants, monoamine oxidase inhibitors (MAOIs) and
serotonin and noradrenaline reuptake inhibitors (SNRIs), RIMA compounds work
on all three neurotransmitters in the body and block degradation and
ultimately increase levels of the three key neurotransmitters associated with
mood, anxiety and somatic disorders."Based on my knowledge of MAOIs, the press release errs in suggesting that RIMAs -- but not MAOIs -- work on "all three" neurotransmitters (serotonin, dopamine, and norepinephrine). The MAOI antidepressants Nardil, Parnate, and Marplan are "'mixed' inhibitors, because they inhibit both Type A and Type B" monoamine oxidase (Thase et al., 1995). "The type B MAO ... has substrate specificity for phenethylamine and dopamine. Type A MAO ... is relatively substrate-specific for norepinephrine, serotonin, and tyramine" (Thase et al.). Even though MAO-A is "relatively specific" to the deamination of norepinephrine, serotonin, and tyramine, there is evidence that suggests that MAO-A is also involved (at least to an extent) in the metabolism of dopamine (Lotufo-Neto et al., 1999).
So, what this means is that is that the "classic" MAOIs *do* elevate the levels of serotonin, norepinephrine, and dopamine ("all three" neurotransmitters) via MAO-A and MAO-B inhibition. And even though the newer RIMAs also "work on" all three chemicals, their effects on dopamine appear to be less pronounced than in the classic MAOIs because of their specificity to MAO-A (which, according to Thase et al., is relatively specific to the deamination of serotonin and norepinephrine).
Tomatheus
==
REFERENCES
Lotufo-Neto, F., Trivedi, M., & Thase, M. E. (1999). Meta-analysis of the reversible inhibitors of monoamine oxidase type A moclobemide and brofaromine for the treatment of depression. Neuropsychopharmacology, 20, 226-47.
Thase, M. E., Trivedi, M. H., & Rush, A. J. (1995). MAOIs in the contemporary treatment of depression. Neuropsychopharmacology, 12, 185-219.
poster:Tomatheus
thread:583436
URL: http://www.dr-bob.org/babble/20051126/msgs/583449.html