The Serotonin System and All that Goes With it

I’ve had some sturm und drang over this post. I’ve been wanting to do a basic post on serotonin, but I’ve also been wanting to do a post on the serotonin theory of depression (and why it is at the very least incomplete). The idea of a serotonin post is a significant challenge, but the idea of trying to explain the serotonin theory of depression WITHOUT a serotonin post is even worse. So my current compromise is to do a post on the serotonin system, and the serotonin theory of depression will be next up. Back to back will keep it all fresh in your minds.
Hang on to your hats:
Serotonin

Oh yeah, she went there. Photo courtesy of The Loom blog from Discover. Sci might have to get one of these…
To begin with, I will admit that I do not know everything there is to know about serotonin. I am able to readily admit this because NO ONE knows everything there is to know about serotonin. This is not just because we haven’t figured it all out yet, but also because the serotonin system is completely, insanely complicated. You perform a pubmed search for “serotonin system review” and you get 176 PAGES of citations, all of them on things like “the serotonin system and anxiety”, “the serotonin system and cardiovascular effects”, “the serotonin system and gastrointestinal effects”, and the list goes on. To do a complete review of all that is currently known about the serotonin system would take hundreds of pages and probably thousands of citations. This is partially because serotonin not only does tons of things, but it does lots of stuff that has very little relation to any of the other stuff that is also doing. You can’t really make any sweeping generalizations about serotonin, there are always exceptions to the rule.
So what I’m going to go into here will be what I know about serotonin, as general as I can make it, and not covering even a quarter of what there is out there. But it will hopefully give you an idea of what people are talking about when they talk about serotonin drugs, serotonin effects, etc.
So here we go.