n.
A molecule with a radionuclide tracer attached, usually used for radioimmunoassay procedures.
Radioligand
| Medical Dictionary: ra·di·o·li·gand |
(rā'dē-ō-lī'gənd, -lĭg'ənd)
n.
n.
| 5min Related Video: Radioligand |
| Veterinary Dictionary: radioligand |
A radioisotope-labeled substance, e.g. an antigen, used in the quantitative measurement of an unlabelled substance by its binding reaction to a specific antibody or other receptor site.
| Wikipedia: Radioligand |
A radioligand is a radioactive biochemical substance (in particular, a ligand) that is used for diagnosis or for research-oriented study of the receptor systems of the body.
In a neuroimaging application the radioligand is injected into the pertinent tissue, or infused into the bloodstream. It binds to its receptor. When the radioactive isotope in the ligand decays it can be measured positron emission tomography (PET) or single photon emission computed tomography (SPECT). In [in vivo] systems it is often used to quantify the binding of a test molecule to the binding site of radio ligand. The higher the affinity of the molecule the more radio ligand is displaced from the binding site and the increasing radioactive decay can be measured by scintillography. This assay is commonly used to calculate binding constant of molecules to receptors.
The transport of the radioligand is described by receptor kinetics.
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History
Radioligands are accredited for making possible the study of biomolecular behaviour, a previously mysterious area of research that had evaded researchers.[1] With this capacity radioligand techniques enabled researchers to identify receptor devices within cells.
Radioactive isotopes commonly used
Main article: Radioactivity in biology
- Tritium, 3H
- Carbon-14, 14C
- Sulfur-35, 35S
- Iodine-131, 131I
- Fluorine-18, 18F
In PET the isotopes fluorine-18 and carbon-11 are often used in molecular neuroimaging.
List of radioligands
Radioligands may be constructed to bind selectively to a particular neuroreceptor or a particular neurotransmitter transporter. Examples of radioligands include:
- 11C-WAY-100635 for the 5-HT1A receptor
- N(1)-([11C]-methyl)-2-Br-LSD ([11C]-MBL) for 5-HT2 receptors[2]
- 18F-altanserin and 18F-setoperone for the 5-HT2A receptor[3]
- 11C-ketanserin[4] and tritiated ketanserin
- 11C-DASB for the serotonin transporter[5]
- 3H-WIN55,212-2 for cannabinoid receptors[6]
- [11C]flumazenil for GABAA receptors.[7]
- (+)PHNO for D2 dopamine receptors.[8]
- [11C]raclopride for D2 dopamine receptors.[9]
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This section requires expansion. |
See also
References
- ^ Niehoff, Debra (2005). The Language of Life: How cells communicate in life & disease. Joseph Henry Press. ISBN 0309089891.
- ^ Wong, Dean F.; Lever, John R.; Hartig, Paul R.; Dannals, Robert F.; Villemagne, Victor; Hoffman, Beth J.; Wilson, Alan A.; Ravert, Hayden T.; Links, Jonathan M.; et al. (1987). "Localization of serotonin 5-HT2 receptors in living human brain by positron emission tomography using N1-([11C]-methyl)-2-bromo-LSD". Synapse 1 (5): 393–398.. doi:. PMID 2905532.
- ^ Karen H. Adams, Lars H. Pinborg, Claus Svarer, S. G. Hasselbalch, Søren Holm, Steven Haugbøl, K. Madsen, Vibe G. Frøkjær, L. Martiny Olaf B. Paulson, Gitte Moos Knudsen (March 2004). "A database of [18F]-altanserin binding to 5-HT2A receptors in normal volunteers: normative data and relationship to physiological and demographic variables". NeuroImage 21 (3): 1105–1113. doi:. ISSN 1053-8119.
- ^ J. C. Baron, Y. Samson, D. Comar, C. Crouzel, P. Deniker, Y. Agid (1985). "Etude in vivo des recepteurs serotoninergiques centraux chez l'homme par tomographie a positions. [In vivo study of central serotoninergic receptors in man using positron tomography]" (in French). Revue Neurologique 141 (8–9): 537–545. PMID 2935920.
- ^ Reimold M, Smolka MN, Zimmer A, et al. (2007). "Reduced availability of serotonin transporters in obsessive-compulsive disorder correlates with symptom severity - a [11C]DASB PET study". J Neural Transm 114 (12): 1603–9. doi:. PMID 17713719.
- ^ Pertwee RG (1999). "Pharmacology of cannabinoid receptor ligands". Curr. Med. Chem. 6 (8): 635–64. PMID 10469884.
- ^ Alexander Hammers, Matthias J. Koepp, Mark P. Richardson, Rene Hurlemann, David J. Brooks & John S. Duncan (June 2003). "Grey and white matter flumazenil binding in neocortical epilepsy with normal MRI. A PET study of 44 patients". Brain 126 (Pt 6): 1300–1308. doi:. PMID 12764053. http://brain.oxfordjournals.org/cgi/content/abstract/126/6/1300.
- ^ Seeman P, Ulpian C, Larsen RD, Anderson PS (August 1993). "Dopamine receptors labelled by PHNO". Synapse 14 (4): 254–262. doi:. PMID 7902615. http://www3.interscience.wiley.com/journal/109702957/abstract.
- ^ Volkow ND, Wang GJ, Fowler JS, Logan J, Franceschi D, Maynard L, Ding YS, Gatley SJ, Gifford A, Zhu W, Swanson JM. (March 2002). "Relationship between blockade of dopamine transporters by oral methylphenidate and the increases in extracellular dopamine: therapeutic implications.". Synapse 43 (3): 181–187. doi:. PMID 11793423.
Further reading
- John Charles Matthews (1993). Fundamentals of Receptor, Enzyme, and Transport Kinetics. CRC Press. ISBN 0849344263.
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