Imidazoline receptor
Imidazoline receptors are the primary receptors on which clonidine and other imidazolines act.[1]
Contents
Classes
There are three classes of imidazoline receptors:[1]
- 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.[2] 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.[2]
Selective Ligands
Agonists
- 7-Me-marsanidine
- Agmatine (endogenous agonist, non-selective, also binds to NMDA, nicotinic, and 2 adrenoceptors)
- Apraclonidine (I1 selective)
- Moxonidine
- Rilmenidine
- Clonidine usually cited as an alpha2 agonist, its structure corroborates recent lab data showing it may be an Imidazole receptor (I1) agonist.[3]
- S-23515
- S-23757
- LNP-509
- MCPP (weak)
- 2-BFI (selective I2 receptor agonist, also NMDA antagonist[4] )
- BU224 (selective I2 receptor agonist, low efficacy)
- LNP-911[5]
- Tizanidine
Antagonists
- 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)
Imidazoline I2 receptor antagonists reversibly block NMDA receptor-mediated Ca2+ influx[6] and thus may inhibit excitotoxicity.
See also
References
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- 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)
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