I think this is a beautiful piece of poetry with great impact, that I had to read again right away. I just have a couple of suggestions.
Perhaps you don't need the second hyphen in 'now-loose-neurons'; the first one I agree is needed to tie the words together, but I wouldn't do it to a noun anyway, and I think it would have more impact as an isolated word.
I also wonder whether 'wall' would work better as the final word; 'wallpaper' seems to lose impact by being a bit too long, and since there are so many kinds of wallpaper it's hard to imagine the one in this image. So for me, it works better as: and flung serotonin against the wall.
To be honest, its taken me a really long time to digest this poem properly. I had a hard time retaining the sense within the poem. I felt rather than saw when I read it. Which offered a different effect of impact.
As for technique, I don't know whether you meant to do it, but the subject abruptly changes in-between. The 1st three lines proceed well, until you reach the middle, there is a sudden change there. Since it is your poem, I will not judge so harshly.
In summation, this poem is very different, and very well done.
It is very heavy, as previously said. My brain linked the picture to your words and went 'what a awesome yet serious way to describe suicide by gunshot wound to the head. (If that was not the intention then pardon my wacky head - blame it on the eye infection working its way into my brain)