The correct answer is bradykinin.
Bradykinin refers to an inflammatory mediator. It refers to a peptide, which makes the blood vessels to enlarge, and thus, make blood pressure to decline.
The chemical bradykinin is released from mast cells at the time of asthma attacks, from walls of the gut as a gastrointestinal vasodilator, from destructed tissues as a pain signal, and may function as a neurotransmitter. It straightforwardly stimulates afferent neurons through G-protein coupled bradykinin B2 receptors.