PATHOLOGY

Detailed explanation-1: -Histamine Induces Vascular Hyperpermeability by Increasing Blood Flow and Endothelial Barrier Disruption In Vivo-PMC. The .

Detailed explanation-2: -Conclusions: Histamine can produce vasodilation of submucosal arterioles by two distinct mechanisms: activation of vascular H1 receptors resulting in release of nitric oxide from endothelium and activation of H3 receptors on sympathetic nerve terminals resulting in presynaptic inhibition of vasoconstrictor tone.

Detailed explanation-3: -Histamine causes constriction of various smooth muscles with the bronchioles being most sensitive to its effects. It also commonly produces vasodilation as a result of effects on vascular smooth muscle.

Detailed explanation-4: -Histamine is a signaling molecule, sending messages between cells. It tells stomach cells to make stomach acid. And it helps our brain stay awake.