Imidazoline receptor

Source: Wikipedia, the free encyclopedia.

Imidazoline receptors are the primary receptors on which clonidine and other imidazolines act.[1][2][3] There are three main classes of imidazoline receptor: I1 is involved in inhibition of the sympathetic nervous system to lower blood pressure,[4] I2 has as yet uncertain functions but is implicated in several psychiatric conditions,[5][6] and I3 regulates insulin secretion.[7]

Classes

As of 2017, there are three known subtypes of imidazoline receptors: I1, I2, and I3.

I1 receptor

The I1 receptor appears to be a

neurocytokine receptor family, since its signaling pathways are similar to those of interleukins.[9] It is found in the neurons of the reticular formation, the dorsomedial medulla oblongata, adrenal medulla, renal epithelium, pancreatic islets, platelets, and the prostate.[8] They are notably not expressed in the cerebral cortex or locus coeruleus.[8]

Animal research suggests that much of the antihypertensive action of

hypoxia.[8]

I2 receptor

The I2 receptor binding sites have been defined as being selective binding sites inhibited by the antagonist

catecholamines.[12] The major binding site is located on the outer mitochondrial membrane, and is proposed to be an allosteric site on monoamine oxidase, while another binding site has been found to be brain creatine kinase.[12][8] Other known binding sites have yet to be characterized as of 2017.[12][13]

Preliminary research in rodents suggests that I2 receptor agonists may be effective in chronic, but not acute pain, including fibromyalgia.[12] I2 receptor activation has also been shown to decrease body temperature, potentially mediating neuroprotective effects seen in rats.[12]

The only known antagonist for the receptor is idazoxan, which is non-selective.[12][8]

I3 receptor

The I3 receptor regulates insulin secretion from pancreatic beta cells. It may be associated with ATP-sensitive K+ (KATP) channels.[14]

Ligands

I1 receptors

Agonists

Antagonists

I2 receptors

Agonists

Antagonists

I3 receptors

No selective ligands are known as of 2017.

Nonselective ligands

Agonists

Antagonists

  • BU99006 (alkylating agent, inactivates I2 receptors)
  • Efaroxan (I1, α2 adrenoceptor antagonist)
  • Idazoxan (I1, I2 antagonist, α2 adrenoceptor antagonist)[12][8]

See also

References

  1. PMID 16529547. Archived from the original
    on April 14, 2013.
  2. PMID 1327589
    .
  3. PMID 1939285
    .
  4. PMID 8725400
    .
  5. PMID 25583220
    .
  6. S2CID 10081479
    .
  7. PMID 16529547
    .
  8. ^
    S2CID 85739305
    .
  9. ^
    S2CID 30065467. Archived from the original
    on 2009-01-08.
  10. PMID 10921526
    .
  11. PMID 11721890
    .
  12. ^
    PMID 28322973
    .
  13. PMID 20832472
    .
  14. PMID 11472276
    .
  15. PMID 10781010
    .
  16. ^
    PMID 25308382
    .
  17. PMID 23741413
    .
  18. PMID 9374795
    .
  19. ^ Bousquet P (2002). "I1 imidazoline receptors: From the pharmacological basis to the therapeutic application" (PDF). Journal für Hypertonie. 6 (4): 6–9.
  20. PMID 20126400
    .

External links
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