Table 1 Histamine Receptors
From: H1 Antihistamines: Current Status and Future Directions
| Â | H1 Receptor | H2 Receptor | H3 Receptor | H4 Receptor |
|---|---|---|---|---|
Receptor expression | Nerve cells, airway and vascular smooth muscle, endothelial cells, epithelial cells, neutrophils, eosinophils, monocytes/macrophages, DC, T and B cells, hepatocytes, chondrocytes | Nerve cells, airway and vascular smooth muscle, endothelial cells, epithelial cells, neutrophils, eosinophils, monocytes, DC, T and B cells, hepatocytes, Chondrocytes | High expression in histaminergic neurons, eosinophils, DC, monocytes; low expression in peripheral tissues | High expression on bone marrow and peripheral hematopoietic cells, eosinophils, neutrophils, DC, T cells, basophils, mast cells |
Histamine function, General | ↑ Pruritus, pain, vasodilation, vascular permeability, hypotension; flushing, headache, tachycardia, bronchoconstriction, stimulation of airway vagal afferent nerves and cough receptors; ↓ atrioventricular node conduction time | ↑ Gastric acid secretion, vascular permeability, hypotension, flushing, headache, tachycardia, chronotropic and inotropic activity, bronchodilation, mucus production (airway) | ↑ Pruritus (no mast cell involvement), ↑ nasal congestion; prevent excessive bronchoconstriction | ↑ Pruritus (no mast cell involvement), ↑ nasal congestion; differentiation of myeloblasts and promyelocytes |
Histamine function in allergic inflammation and immune modulation | ↑ Release of histamine and other mediators; ↑ cellular adhesion molecule expression and chemotaxis of eosinophils and neutrophils; ↑ antigen-presenting cell capacity, costimulatory activity on B cells; ↑ cellular immunity (Th1), ↑ autoimmunity; ↓ humoral immunity and IgE production | ↑ Eosinophil and neutrophil chemotaxis;↓ IL-12 by dendritic cells; ↑ IL-10 and development of Th2 or tolerance-inducing dendritic cells; ↑ humoral immunity;↓ cellular immunity; suppresses Th2 cells and cytokines; indirect role in allergy, autoimmunity, malignancy, graft rejection | Probably involved in control of neurogenic inflammation through local neuron-mast cell feedback loops; ↑ proinflammatory activity and APC capacity | ↑ Calcium flux in human eosinophils; ↑ eosinophil chemotaxis; ↑ IL-16 production (H2 receptor also involved) |
Histamine function in the CNS | Sleep/wakefulness, food intake, thermal regulation, emotions/aggressive behavior, locomotion, memory, learning | Neuroendocrine | Presynaptic heteroreceptor; ↓ histamine, dopamine, serotonin, noradrenaline, and acetylcholine release | To be defined |