The amount of a pituitary adenylate cyclase-activating polypeptide type I receptor when measured in blood serum. The trait is level of pituitary adenylate cyclase-activating polypeptide type I receptor in blood serum (OBA_2040511, an Ontology of Biological Attributes term). Also known as: blood serum pituitary adenylate cyclase-activating polypeptide type I receptor amount.