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Re: Depression change in brain anatomy

Posted by linkadge on June 10, 2007, at 16:31:56

In reply to Re: Depression change in brain anatomy, posted by FredPotter on June 10, 2007, at 15:49:55

>A lot has happened in our understanding of >depression in the last 10 years.viz depressed >people have fewer glia cells in the prefrontal >cortex and the hippocampus is shrunk.

I agree.


>It seems these things may predispose to >depression, requiring some kind of "stress" for >its realisation, but it also seems these >features are themselves worsened (further >damaged) by depressive episodes making the >episodes more likely as we get older.

I also agree.


>During the decade unequivocal evidence for >neuron regeneration has been discovered, >particularly in the hippocampus. So this is the >good news, especially as serotonin, via the >serotonin transporter leads to more BDNF which >promotes neuron growth.


This is where I partially disagree. While I do agree that depression may be due to decreased cellular resiliance and repair, I would not go as far as some have to suggest that SSRI's fix this problem. Yes there are some studies that show SSRI's can increase BDNF, but there are also studies that show SSRI's do not increase BDNF. Some studies show only temporary, or biphasic changes in BDNF protien, Ie quick upregulation that peters off after a few weeks.

Also, the word is not final on SSRI's and neurogenesis. Some studies show enhanced neurogenesis with antidperessants, some studies don't. Also, serotonin isn't the only neurotransmitter involved in hippocampal placiticy. Dopamine, choline, noradrenaline, gaba are also involved. Who knows if tweaking one chemcial will actually make things better or worse down the road.

Also, serotonin can trigger cellular proliferation in the perihpery. 5-ht2b agonists like the recently withdrawn parkinsons meds can affect cellular differentiation in the heart. I think it is possable that SSRI's are capable of affecting cardiac valves in the same way.

SSRI's also do not fix the circutry (ie glia atrophy or dysfunction) that may be involved in depression, nor do they undoe atrophy in the frontal cortex.

A number of studies also suggest that SSRI's "worsen" stress induced hippocampal atrophy. This study suggests that tianeptine prevents stress induced atrophy by lowering serotonin levels.

See:

http://www.aapspharmaceutica.com/search/view.asp?ID=29864&size=small

http://www.jneurosci.org/cgi/content/full/22/9/3638

So, I don't think the word is final on how these drugs affect the brain, or wheather they are actually doing all that they are purported to do.

Linkadge


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poster:linkadge thread:761153
URL: http://www.dr-bob.org/babble/20070604/msgs/762219.html