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Nebrisi EE, Prytkova T, Lorke DE, Howarth L, Alzaabi AH, Yang KHS, Howarth FC, Oz M. Capsaicin Is a Negative Allosteric Modulator of the 5-HT 3 Receptor. Front Pharmacol 2020; 11:1274. [PMID: 32982728 PMCID: PMC7490547 DOI: 10.3389/fphar.2020.01274] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2020] [Accepted: 07/31/2020] [Indexed: 01/16/2023] Open
Abstract
In this study, effects of capsaicin, an active ingredient of the capsicum plant, were investigated on human 5-hydroxytryptamine type 3 (5-HT3) receptors. Capsaicin reversibly inhibited serotonin (5-HT)-induced currents recorded by two-electrode voltage clamp method in Xenopus oocytes. The inhibition was time- and concentration-dependent with an IC50 = 62 μM. The effect of capsaicin was not altered in the presence of capsazepine, and by intracellular BAPTA injections or trans-membrane potential changes. In radio-ligand binding studies, capsaicin did not change the specific binding of the 5-HT3 antagonist [3H]GR65630, indicating that it is a noncompetitive inhibitor of 5-HT3 receptor. In HEK-293 cells, capsaicin inhibited 5-HT3 receptor induced aequorin luminescence with an IC50 of 54 µM and inhibition was not reversed by increasing concentrations of 5-HT. In conclusion, the results indicate that capsaicin acts as a negative allosteric modulator of human 5-HT3 receptors.
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Affiliation(s)
- Eslam El Nebrisi
- Department of Pharmacology, College of Medicine and Health Sciences, UAE University, Al Ain, United Arab Emirates.,Department of Pharmacology, Dubai Medical College, Dubai Medical University, Dubai, United Arab Emirates
| | | | - Dietrich Ernst Lorke
- Department of Anatomy and Cellular Biology, Khalifa University, Abu Dhabi, United Arab Emirates.,Department of Cellular Biology and Pharmacology, Herbert Wertheim College of Medicine, Florida International University, Miami, FL, United States
| | - Luke Howarth
- Department of Pharmacology, College of Medicine and Health Sciences, UAE University, Al Ain, United Arab Emirates
| | - Asma Hassan Alzaabi
- Department of Pharmacology, College of Medicine and Health Sciences, UAE University, Al Ain, United Arab Emirates
| | - Keun-Hang Susan Yang
- Department of Biological Sciences, Schmid College of Science and Technology, Chapman University, Orange, CA, United States
| | - Frank C Howarth
- Department of Physiology, College of Medicine and Health Sciences, UAE University, Al Ain, United Arab Emirates
| | - Murat Oz
- Department of Pharmacology and Therapeutics, Faculty of Pharmacy, Kuwait University, Safat, Kuwait
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