the histamine h1 receptor is one of several existing histamine g protein-coupled receptors. depending on many factors, including the type of receptor, histamine can trigger a variety of responses, including vasodilation, smooth muscle contraction, stimulation of gastric secretion, cardiac stimulation, and increased vascular permeability (causing runny nose and watery eyes).which of the following could account for the different cellular responses to histamine? select all that apply.