Thioperamide

Thioperamide is a histamine H3 receptor antagonist with Ki values of 4.3 nM at the H3 receptor and 31 nM at the H4 receptor. It has been used in scientific research to help elucidate the function of the histamine H3 receptor, with the development of a radiolabelled form of thioperamide allowing the distribution of H3 receptors in the brain to be mapped by autoradiography.

Chemistry

Thioperamide is a derivative of imidazole, a common scaffold in pharmacology due to its ability to mimic the structure of histamine. The methyl group attached to the imidazole ring of thioperamide is thought to interact with a lipophilic binding pocket on the H3 receptor, enhancing its affinity for the receptor.

Pharmacology

Thioperamide acts as an antagonist at the histamine H3 receptor, meaning it binds to the receptor and prevents it from being activated by histamine. This has the effect of increasing the release of histamine in the brain, as the H3 receptor normally acts to inhibit histamine release. Thioperamide also has some affinity for the H4 receptor, although it is less potent at this receptor than at the H3 receptor.

Clinical significance

The ability of thioperamide to increase histamine release in the brain has led to it being investigated for potential use in the treatment of neurological disorders such as Alzheimer's disease and narcolepsy. However, due to its poor bioavailability and the presence of side effects such as insomnia and anxiety, thioperamide has not been developed for clinical use.

See also

• Histamine H3 receptor
• Histamine H4 receptor
• Imidazole

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