There are three classes of imidazoline receptors:
- I1 receptor – mediates the sympatho-inhibitory actions of imidazolines to lower blood pressure, (NISCH or IRAS, imidazoline receptor antisera selected)
- I2 receptor – an allosteric binding site of monoamine oxidase and is involved in pain modulation and neuroprotection
- I3 receptor – regulates insulin secretion from pancreatic beta cells
Activated I1-imidazoline receptors trigger the hydrolysis of phosphatidylcholine into DAG. Elevated DAG levels in turn trigger the synthesis of second messengers arachidonic acid and downstream eicosanoids. In addition, the sodium-hydrogen antiporter is inhibited, and enzymes of catecholamine synthesis are induced. The I1-imidazoline receptor may belong to the neurocytokine receptor family, since its signaling pathways are similar to those of interleukins.
- Agmatine (endogenous agonist, non-selective, also binds to NMDA, nicotinic, and 2 adrenoceptors)
- Apraclonidine (I1 selective)
- Clonidine usually cited as an alpha2 agonist, its structure corroborates recent lab data showing it may be an Imidazole receptor (I1) agonist.
- MCPP (weak)
- 2-BFI (selective I2 receptor agonist, also NMDA antagonist )
- BU224 (selective I2 receptor agonist, low efficacy)
- Efaroxan (non-selective, binds to I1 receptor and α2 adrenoceptor)
- Idazoxan (non-selective, binds to I2 receptor and α2 adrenoceptor)
- BU99006 (alkylating agent, inactivates I2 receptors)
- Head GA, Mayorov DN (January 2006). "Imidazoline receptors, novel agents and therapeutic potential". Cardiovasc Hematol Agents Med Chem 4 (1): 17–32.
- Ernsberger P (June 1999). "The I1-imidazoline receptor and its cellular signaling pathways". Ann. N. Y. Acad. Sci. 881 (1): 35–53.
- Reis DJ, Piletz JE (November 1997). "The imidazoline receptor in control of blood pressure by clonidine and allied drugs" (pdf). Am. J. Physiol. 273 (5 Pt 2): R1569–71.
- Han, Z; et al. (2013). "Fast, non-competitive and reversible inhibition of NMDA-activated currents by 2-BFI confers neuroprotection.". PLoS One (2014) 8 (5): e64894.
- Bousquet P (2002). "I1 imidazoline receptors: From the pharmacological basis to the therapeutic application" (pdf). Journal für Hypertonie 6 (4): 6–9.
- Jiang SX, Zheng RY, Zeng JQ, Li XL, Han Z, Hou ST (March 2010). "Reversible inhibition of intracellular calcium influx through NMDA receptors by imidazoline I(2) receptor antagonists". Eur. J. Pharmacol. 629 (1–3): 12–9.
- Imidazoline Receptors at the US National Library of Medicine Medical Subject Headings (MeSH)
- imidazoline receptor 2 at the US National Library of Medicine Medical Subject Headings (MeSH)
- imidazoline I1 receptors at the US National Library of Medicine Medical Subject Headings (MeSH)