Rahul Sharma (Editor)

Imidazoline receptor

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Imidazoline receptors are the primary receptors on which clonidine and other imidazolines act. There are three main classes of imidazoline receptor: I1 is involved in inhibition of the sympathetic nervous system to lower blood pressure, I2 has as yet uncertain functions but is implicated in several psychiatric conditions, and I3 regulates insulin secretion.

Contents

Classes

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.

    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.
  • S-23515
  • S-23757
  • LNP-509
  • MCPP (weak)
  • 2-BFI (selective I2 receptor agonist, also NMDA antagonist )
  • BU224 (selective I2 receptor agonist, low efficacy)
  • LNP-911
  • 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 and thus may inhibit excitotoxicity.

    References

    Imidazoline receptor Wikipedia
    (Text) CC BY-SA