Hello. I Have Just Started Taking Cymbalta And I Am

Hello. I have just started taking Cymbalta and I am still taking Wellbutrin. The Idea is to eventually take me off of Wellbutrin. I understand that Cymbalta works on two of the three chemicals norephrine and serotonin does Wellbutrin work on the third brain chemical that I do not know the name of?
Thank you,
Emily