Histamine Receptors

Question 1

H1 1.) Distribution 2.) Post Receptor Signaling 3.) Biological consequences of Receptor Activation

Answer 1

1. ) Smooth muscle, endothelium, peripheral neurons, brain
2. ) Gαq, ↑ IP3, DAG,
3. ) ↑ pruritus (itch), pain, secretion from mucosa, vasodilation (via NO), edema, bronchoconstriction, contraction of the gut

Question 2

H2 1.) Distribution 2.) Post Receptor Signaling 3.) Biological consequences of Receptor Activation

Answer 2

1. ) Gastric mucosa (parietal cells), cardiac muscle, vascular smooth muscle, mast cells, basophils, brain
2. ) Gαs, ↑ cAMP
3. ) ↑ gastric acid secretion, vasodilation (via cAMP), heart rate

Question 3

H3 1.) Distribution 2.) Post Receptor Signaling 3.) Biological consequences of Receptor Activation

Answer 3

1. ) Presynaptic histaminergic neurons in brain, myenteric plexus, and other neurons
2. ) Gαi, ↓ cAMP
3. ) ↓ neurotransmitter release (e.g. histamine)

Question 4

H4 1.) Distribution 2.) Post Receptor Signaling 3.) Biological consequences of Receptor Activation

Answer 4

1. ) Cells of hematopoietic origin including eosinophils, neutrophils, dendritic cells, basophils, monocytes, T cells
2. ) Gαi, ↓ cAMP
3. ) Differentiation of myeloblasts and promyelocytes, chemotaxis, secretion of cytokines, upregulation of adhesion factors