Man, the abstinence movement rhetoric about oxytocin is weird.
Never mind that the scientific basis is pretty shaky. Never mind that it's creepy as shit to assign love to a chemical released at orgasm. Never mind that apparently marriage is so sacred that it alters your biochemistry.
I just think it's weird to A) need any scientific backing for the statement "ending relationships causes emotional pain" and B) use that as an argument against having any relationships at all. It makes them sound like cranky old divorcees. I know, going into a relationship, that it's going to end and that it's going to suck when it does. I just believe that the stuff in between is worth it.
I don't know the name of the specific neurotransmitter involved here, but I'm pretty damn sure that going to bed alone every night for goddamn years isn't entirely emotionally painless either.