Inverse agonist

Image:Inverseagonist.gif In pharmacology, an inverse agonist is an agent which binds to the same receptorbinding-site as an agonistfor that receptor but exerts the opposite pharmacological effect. Inverse agonists are effective against certain types of receptors (e.g. certain histamine receptors / GABA receptors) which have intrinsic activity without the acting of a ligand upon them (also referred to as 'constitutive activity'.)

The net effect of inverse agonist is similar to that of receptor antagonists; both classes of agents decrease the overall activity of a given receptor. However, as antagonists function by blocking the action of agonists (thereby decreasing the activity level indirectly), the maximum effect an antagonist can have is to reduce receptor activity to zero. An inverse agonist, on the other hand, can reduce the activity level well below the baseline of that receptor.

One particular example is R015-4513which the inverse agonist of the benzodiazepineclass of drugs (such as Xanaxand Valium). R015-4513and the benzodiazepinesboth utilize the same GABA binding site on neurons, yet R015-4513has the opposite effect, producing severe anxiety rather than the sedative effect of the benzodiazepines.

References

• Pharmacology of benzodiazepine receptors: an updateby W. Sieghart in Journal of Psychiatry & Neuroscience (1994) Volume 19, pages 24-29.
• "Ethanol potentiation of GABAergic transmission in cultured spinal cord neurons involves gamma-aminobutyric acidA-gated chloride channels" by A. K. Mehta and M. K. Ticku in The Journal of Pharmacology and Experimental Therapeutics (1988) Volume 246, pages 558-564. PMID 2457076

See also

• Agonist
• Receptor antagonist

External links

• Inverse Agonists for Medical Studentsby William B. Jeffries, Ph.D., Creighton University Department of Pharmacologyfr:Agoniste inverse

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It uses material from the http://en.wikipedia.org/wiki/Inverse+agonist Wikipedia article Inverse agonist.