Imidazoline receptor

Imidazoline receptors are the primary receptors on which clonidine and other imidazolines act.^[1]

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]

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

Imidazoline I₂ receptor antagonists reversibly block NMDA receptor-mediated Ca²⁺ influx^[6] and thus may inhibit excitotoxicity.

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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