Bumping up this interesting article from Neurotalk's sister site PsychCentral, about chronic pain and anxiety being connected :

Chronic Pain and Anxiety Linked By Neurotransmitter | Psych Central News

The article is brief in detail but further research of the term "pituitary adenylate cyclase activating polypeptide" leads to more information on how widely this neurotransmitter can affect the body. Here's a couple of links to relevant abstracts but there's more out there:

Pituitary adenylate cyclase-activating polypeptide and its receptors: 2 years after the discovery. - PubMed - NCBI

The origin and function of the pituitary adenylate cyclase-activating polypeptide (PACAP)/glucagon superfamily. - PubMed - NCBI