It is the study of neurons in your gut. We each have two brains, the big one in our head that gets all the attention, and the little one in your guts. Yes, there are seratonin receptors in the gut, along with numerous other neurotransmitters.
I have often wondered about the effects of bipolar on my body. I know how it affects my thinking and mood, but what about other things? Like when I was a kid, I used to get awful stomach pains before gym class, my all time most hated class. Later on someone told me that stomach pain in children is sometimes a type of migraine, which I ended up getting throughout most of my adolescence. Which I later found out is part of being bipolar.
There are other funny things about neurogastroenterology. Like this thing I have discovered recently where I feel physically ill around women I find attractive. I live in sheer terror of the day I meet someone so cute I puke all over them.