Posted by linkadge on August 23, 2007, at 22:17:12
In reply to Re: Nardil completely suppresses REM sleep » linkadge, posted by Girlnterrupted78 on August 23, 2007, at 3:00:34
Well, I wouldn't say this study actually proves that REM supression doesn't have antidepressant effect in some people, only that some people don't respond to REM supressors as antidepressants.
Different types of depression respond to different types of antidepressants. There are a few antidepressants that do not reduce REM sleep, (only two that I know of, namely bupropion and a TCA called trimipramine).
But, the thing is that there are types of depression for which those drugs are completely ineffective.
There is a link between the activity of the monoamines and REM sleep.
If you reduce REM sleep, you will actually increase serotonin in the hippocampus. (This is independant of the use of serotonergic drugs). Ie if you reduce REM sleep in an animal by non serotonergic drugs, you will still increase the serotonin content of the hippocampus.
There are other neurotransmitters that are altered by REM supression. Infact, continued REM supression produces a number of the same adaptive changes that are evident with long term AD administration, namely downregulation of 5-ht2a receptors, increased sensitivty of d2 receptors etc.
The mechanism of antidepressant effect of total sleep deprivation is not completely known but seems to involve many neurotransmitter systems. It seems to have a psychostimulant like effect. It can reduce hyperactive limbic metabolsm. It can increase the activity of monoamines. It can decrease the seizure threshold.
Complete relapse can happen if patients take even the shortest of naps. As little as 1 minaute of REM sleep recorded on and EEG can result in complete relapse.
I personally think that its got to do with affecting the cholinergic/monoaminergic ballance.
If you stress an animal, it will begin to show the exact same patterns of REM sleep that are evident in depresion. I think this is an adaptive responce. The brain is increasing the REM duration to try and put more brain processing into emotionally relavant material. (Ie to try and process the stressfull events). The REM induced increase in cholinergic activity reduces monoaminergic neurotransmission which makes it difficult to move forward.
Roughtly speaking cholinergic activity lets one reflect on previously established connections, wherase the monoamines promote the growth of new connections.
Linkadge
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URL: http://www.dr-bob.org/babble/20070815/msgs/778214.html