<prompt> Histamine causes all EXCEPT:Aeriolar dilatationIncreased permeability of venulesConstriction of large aeriesPlatelet aggregation  <response>: Platelet aggregation REF: Robbins pathology 7th edition page 63 Preformed histamine is present in mast cell granules and is released by mast cell degranulation in response to variety of stimuli. In humans histamine causes: Aeriolar dilatation Increased permeability of venules however constricts large aeries Via binding to H1 receptor on endothelial cells 