Vasoactive intestinal peptide (VIP) (Tsukada T et al, 1985) belongs to the glucagon hormone family and is expressed in many parts of the human body. VIP causes vasodilation, lowers arterial blood pressure, stimulates myocardial muscle contraction and increases glycogenolysis. It also relaxes the smooth muscle of trachea, stomach and gall bladder. The effects of VIP are mediated by the VIP receptors of which there are two, 1 and 2 (Sreedharan SP et al, 1993 and Svodoba M et al, 1994 respectively). The actions of the receptor are mediated by coupling with the G protein alpha s subunit, which stimulates adenylyl cyclase which increases intracellular cAMP levels (Sreedharan SP et al, 1993).