TABLE 1

Overview human histamine receptor subtypes (hH1 receptor-hH4 receptor).

hH1RhH2RhH3RhH4R
Chromosomal gene location3q255q35.220q13.3318q11.2
Amino acids487359445390
Isoformsat least 20 (65, 66)>3
G protein couplingGαq/11GαsGαi/oGαi/o
Constitutive activity++++++
Signal transductionPLC↑, Ca2+cAMP↑cAMP↓, Ca2+↑, MAPK↑cAMP↓, Ca2+↑, MAPK↑
Tissue localizationsUbiquitous (mainly lung, CNS, blood vessels)Ubiquitous (mainly stomach, heart, CNS)Neurons (CNS and PNS)Bone marrow, hematopoietic cells
Physiologic relevanceBronchoconstriction, vasodilation, food intake, sleep-wake regulationGastric acid secretionNeurotransmitter release (→ sleep-wake regulation, attention/cognition, food intake)Immune responses (→ chemotaxis, IL-, IFN-modulation)
Pathophysiological conditionsAllergic reactions, emesis, sleep-wake disordersGastric ulcersCognitive impairment, schizophrenia, sleep-wake disorders, epilepsy, pain, etc.Inflammatory diseases (allergy, asthma, pruritus, arthritis), pain, etc.
  • + and ++, extent of constitutive activity; PL, phospholipase; PNS, peripheral nervous system.