Posted by Pfinstegg on October 23, 2002, at 18:26:22
In reply to Re: To Pfinstegg » glenn, posted by Pfinstegg on October 22, 2002, at 21:42:10
Actually, I made a couple of mistakes and over-simplifications in my last post to you. On further reading, the cortisol-hippocampus situation is more complex than I had realized. For example, most antidepressants, including lithium (which I had mistakenly excluded), the tricyclics, SSRI's and oddballs like tianeptine all have a beneficial effect on the hippocampus, even though they don't lower the serum or CSF cortisol itself. Cortisol is supposed to make the hippocampus produce excitatory amines, like glutamate and NMDA, which stop the hippocampus from producing new dendrites and new neurons (in rats, about 4000 new neurons are produced per day when the rats are unstressed). The new neurons and dendrites are thought to be vital for memory and spatial learning. All the ADs, not just the SSRI's, are thought to increase neurotransmission at the 5HTA-1 receptors, which, by damping down glutamate and NMDA in some way not yet well understood, protect the hippocampus so that it can keep on producing new dendrites and some new neurons. Having read more about hippocampal shrinkage, it is not quite as bad as I had thought: the neurons don't actually die, usually, but they become smaller through loss of their dendrites and poorer metabolic functioning- also probably through loss of the supporting glial cells (white matter).
So shrinking hippocampuses, at least potentially, are reversible - good news!. Apparently, researchers haven't yet begun to do long-term studies of various ADs, cortisol levels and hippocampal size, but there is now much pressure from neurophysiologists to do so, both on the traditional ones and on the newer ones.
I also discovered that it isn't all about high cortisol! a recent NIH publication indicated that there is evidence that atypical depression involves LOW, rather than high cortisol, and should be treated with activating medications, rather than ADs, mentioned in the last paragraph, that indirectly modify the effects of high cortisol. Apparently the easiest way to tell if you have atypical is to notice when you feel best- it's morning for atypical, and evening for typical.
Pfinstegg
poster:Pfinstegg
thread:124700
URL: http://www.dr-bob.org/babble/20021019/msgs/124915.html