Trazodone isn't strictly an SSRI - it's also a strong alpha-1-blocker, which is the main reason why it has a sedative effect. Most anti-psychotics also potently block alpha-1-adrenergic receptors - which is again, the main reason for their sedative effects. The antihistamine effect amplifies the adrenergic blockade effects...Trazodone has part of that property...
Serotonin really doesn't alleviate insomnia...in fact, it can cause it...the only time serotonin has a specific anti-insomnia effect is when it converts into melatonin.
'Serotonin' doesn't do anything per se. It depends on what part of the brain it's working on and what receptors. What you like to specify a little? Be aware that an antagonist doesn't necessarily do the opposite of an agonist. 5HT2c antagonism increases dopamine in the Ventral Tegmental Area. Although agonism can lower the dopamine, 5HT2c agonism is also hallucinogenic and a component of psychedelics like acid along with 5HT2a agonism. Mu (endorphin/opioid) agonists cause analgesia and pleasure. Mu antagonists don't cause pain or dysphoria. Unless you are addicted to opiates, they don't really seem to change much. H1 antagonists will knock you out. H1 agonists will not wake you the hell up.
Trazodone's primary mode of sedation is H1 antagonism, not alpha 1 antagonism.
With that being said, serotonin does have anxiolytic / calming properties via 5-HT1A autoreceptors - the reasons are more complicated than most think. Autoreceptors reduce the activity of a neurotransmitter, therefore serotonin 1A inhibits itself, therefore producing a decrease in serotonergic excitation at other receptors.
So it's actually the DECREASE in serotonin via autoreceptor activation that produces less anxiety....
Also 5-HT1A is negatively coupled to adenylate cyclase and it has diverse effects on neuropeptides, the other anxiolytic effect probably has to do with 5-HT1A being present on oxytocinergic neurons.
Therefore 5-HT1A receptor activation is just about the only serotonin receptor that alleviates anxiety. It does so by.
- Reducing serotonin at other receptors.
- Increasing oxytocin releasee
Jeeee-sus. OK, here we go. First of all, not all 5HT1A receptors are autoreceptors, there are post-synapatic ones too. The effect of autoreceptors on the release of a neurotransmitter can be extraordinarily complicated. Look up the drug amisulpride and see how it's effect on dopaminergic transmission changes with the dose. It effects D2 receptors, which tend to be auto receptors. Oh yeah, btw. You'd think that activating D2 receptors would relieve schizophrenia, as they are autoreceptors, and reduce dopaminergic activity, right? Well, it's much more complicated than that. It turns out that D2 antagonists, and the later discovered 5HT2a antagonists, are what work. D2 agonists like pramipexole can make schizophrenia worse.
To assume that the decrease in anxiety from 5HT1A activation is due to reduced serotonin is jumping the gun. The newest SSRIs, sometimes called atypical SSRIs, are vilazodone and vortioxetine. They are both strong SSRIs. Vilazodone is a partial 5HT1a agonist and vortioxetine is a bit weaker on the SSRI side and is a full 5HT1a agonist (well, nearly full). They seem to be potent anxiolytics, much more so than standard SSRIs. According do your hypothesis, this shouldn't be the case. If all it took were 5HT1a agonism, than Buspar would be the most effective anxiolytic out there. But it's not prescribed often because for most people, it just doesn't work.
I'm trying to not be a dick-ish, but you need to hold off on making these extrapolations from limited data. Start with a hypothesis and build from there, find more data to support it, and in your case, look for contradictory data and confounding variables. This shit is super complicated, and needs to be approached as such. Do not do this:
HOWEVER, these receptors can easily become de-sensitized if you stimulate them too much, leading to nullification of this effect and thus lack of anxiolytic effect from serotonin....this is one of the hypothesis of violent criminals, they no longer respond to the autoreceptors of serotonin thus there are no brakes and serotonin is flooding the brain leading to erratic behavior.
That is a whopping conclusion that would need a lot of data and sources to back it up. Large amounts of serotonin as a result of SRIs do not seem to cause erratic behavior, but rather numbness. Ironically, SRAs (Serotonin Releasing Agents), seem to do the opposite (see the complexity?). One gene associated with some criminal behavior seems to be the "Warrior Gene", which reduces the amount of MAOA-I in the system. This increase a lot of neurotransmitters, including serotonin, dopamine and norepinephrine. We know very little about what genes and neurotransmitters cause criminal behavior, unfortunately.
Another example of how paradoxical this can be is Amphetamines vs. Intuniv for ADHD. Both help with ADHD. However, amphetamines increase norepinephrine, and Intuniv decreases it. It seems that with amphetamines, the norepinephrine increase aids in focus. With the Intuniv, the decrease in NE seems to help the brain's attention not be pulled away by random stimuli. allowing the person to concentrate on what's on task. The difference seems to be in what parts of the brain the increase or reduction of NE occurs.
I don't want to be disrespectful, but it may seem like it a little. I'm just trying to be as straight-forward as possible. These things complicated and need to be treated as such. You need to use doubt as your foundation of research, not assuredness.
I'm hesitant to post this yet, but I am working on a Youtube channel sharing a lot of what I know. All the videos are drafts, and I was planning to improve before I posted. But would you be interested in seeing it?
Edited by OneScrewLoose, 28 April 2015 - 01:23 AM.