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Valentine Log

Final Project: The Effect of Capsaicin on Mammalian Tissues

Article: [|The capsaicin receptor: a heat-activated ion channel in the pain pathway]
 * [Full Marks JCB]**


 * Pain is perceived when a group of sensory neurons called nociceptors, are triggered by external stimuli and relay information on the resulting tissue damage, to the brain and spinal cord. These neurons tend to be very sensitive to capsaicin, a major component of spicy foods, and exposure to it can lead to a "burning sensation" for mammals. Long term exposure could end up deteriorating the nociceptor's sensitivity to external stimuli and possibly destroy the neuron.
 * The exact mechanism of how capsaicin elicits the sensation of pain upon the nociceptors is unknown. The most likely explanation to capsaicin's mechanism of action is through activation of a receptor on the sensory neuron.
 * Cloning of a gene that encodes a capsaicin receptor helps to better understand the association between capsaicin and pain sensation. The capsaicin receptor is activated when temperatures are raised to a level that could cause pain.


 * Vanilloid Receptor Subtype 1 (VR1) was created from cloning of cDNA in order to obtain more information on the characteristics of the capsaicin receptor. Observation of the influx of calcium ions, was used as a guide to identify if the findings were consistent with that of a capsaicin activated receptor.


 * The pharmacological properties of the cloned vanilloid receptor were compared with those of other native vanilloid receptors. The receptors' responses to vanilloid agonists and antagonists were also analyzed and compared.
 * The cloned VR1 was then tested with several different samples of pepper extracts in order to determine if the sensation of heat generated from each sample, would be consistent with their rank as effective activators for the receptor.
 * The VR1 was then tested with several different activators for sensory neurons, in order to identify a possible relationship between capsaicin and a well-known chemical moderator of things done by nociceptors.


 * Tests were done to determine the electrophysiological properites of VR1 throughout the entire cell and at lone channel points. Examination of its current-voltage associations also showed that VR1 was significantly more permeable to calcium ions than to other divalent cations.
 * Analysis of the electrophysiological properties of the vanilloid receptors have also shown occurrences of desensitization which was determined to be dependent upon the presence of extracellular calcium ions.
 * Capsaicin-evoked responses were examined on small patches removed from other cells. The capsaicin produced similar responses when added to both the extracellular and intracellular sides of the plasma membrane from a patch removed from a cell. As a result, it is proposed that the vanilloid receptors contain binding sites for capsaicin on both sides of the plasma membrane.


 * Long-term treatment of capsaicin with non-neuranol cells that expressed vanilloid receptors resulted in destruction of the cell.


 * The biological components and characteristics of VR1 cDNA are described.
 * VR1 was suspected of having a relationship with store-operated calcium channels (SOCs) due to several significant similarities between it and a few SOC examples. After analysis of its calcium reliant inner currents, it was confirmed that VR1 does not function as an SOC.
 * VR1 may possibly be linked with human EST clones due to the high similarities they share in nucleotide sequence and amino-acid levels.


 * Expression of VR1 with a very specific group of sensory neurons, in trigeminal and dorsal root ganglia shows that it is consistent with the fact that the vanilloid receptors are highly selective.


 * Capsaicin induced responses from vanilloid receptors were found to be associated with the activity accompanying a vanilloid receptor following fast increases in temperature.
 * The activity following the expression of VR1 in oocytes was then compared with its activity observed after a rapid increase in temperature. These observations reinforced the fact that the capsaicin receptor is stimulated by heat that is relatively toxic.


 * Protons were suspected of being capable of activating or moderating capsaicin induced responses in vanilloid receptors. After observing the effects from addition of hydrogen ions and reduction in pH levels on VR1 expression, it was confirmed that even though protons weren't capable of stimulating the capsaicin receptor, it was still capable of influencing and augmenting capsaicin-evoked responses.


 * Examination of the target of capsaicin action was thought to underscore significant biological processes that would lead to its overall mechanism of pain perception and control.
 * The molecular target of capsaicin induced action was determined to be an ion channel and is also fundamentally comparable to the TRP group of ion channels. Although the exact purpose and mechanism of action for these ion channels are not entirely known, the ion channels for VR1 are still expected to serve an array of biological functions, due to its association with TRP family members.
 * The capsaicin receptor is thought to be triggered by thermal stimuli. Capsaicin-evoked responses are also thought to go hand in hand with heat mediated responses.
 * Protons have also been shown to have an influence on the response from VR1 expression.
 * The study of VR1 could aid in the development of new drugs or painkillers due to many of the results that come from its expression.


 * A detailed step of how the Expression cloning of the VR1 was performed along with an analysis of the DNA is displayed. The DNA was determined to have originated from within a rat.
 * Details the electrophysiological processes applied to the VR1 within the oocytes.
 * The procedure for the electrophysiological analysis of the mammalian cells along with contents of each solution used and the calculations used to tabulate the unknowns, were all described.
 * The route taken to quantitatively analyze the cell death as a result of prolonged exposure to capsaicin was explained. The analysis of the northern blot as well as the analysis of the histochemistry for the //in situ// hybridization, was depicted comprehensively.


 * FAQ Question**

22. Find a source or database that lists the molecular symmetry operations and point group of a compound.
[|3DMolSym] 3DMolSym is an online program that allows students to view the molecular structure of a wide range of molecules as well as their symmetry operations and point groups. It provides a 3D animation of the symmetry elements for each molecule to aid in visualization. It also allows students to rotate the molecule, zoom in or out and also adjust the display of the molecule to "Ball n' Stick", "Space Filling" etc. Here's an example of a few of the symmetry elements of ammonia being viewed on 3DMolSym:


 * Sources for Final Paper**
 * 1) Baumann, T. "Responses of Adult Human Dorsal Root Ganglion Neurons in Culture to Capsaicin and Low PH." //Pain// 65.1 (1996): 31-38. //ScienceDirect//. Sciverse, 12 Mar. 1999. Web. 1 Dec. 2011. [|doi]
 * 2) Bleakman, D., J. R. Brorson, and R. J. Miller. "The Effect of Capsaicin on Voltage-gated Calcium Currents and Calcium Signals in Cultured Dorsal Root Ganglion Cells." //British Journal of Pharmacology// 101.2 (1990): 423-31. //British Journal of Pharmacology//. PubMed Central. Web. 28 Nov. 2011. [|doi]
 * 3) Caterina, Michael J., Mark A. Schumacher, Makoto Tominaga, Tobias A. Rosen, Jon D. Levine, and David Julius. "The Capsaicin Receptor: a Heat-activated Ion Channel in the Pain Pathway." //Nature 389// (1997): 816-24. //Nature//. Nature Publishing Group, 24 Sept. 1997. Web. 19 Nov. 2011. [|doi]
 * 4) Cholewinski, A., G. Burgess, and S. Bevan. "The Role of Calcium in Capsaicin-induced Desensitization in Rat Cultured Dorsal Root Ganglion Neurons." //Neuroscience// 55.4 (1993): 1015-023. //ScienceDirect//. Sciverse, 18 Mar. 2003. Web. 28 Nov. 2011. [|doi]
 * 5) Dray, A. "Mechanism of Action of Capsaicin-like Molecules on Sensory Neurons." //Life Sciences// 51.23 (1992): 1759-765. //ScienceDirect//. Sciverse, 16 Nov. 2002**a**. Web. 28 Nov. 2011. [|doi]
 * 6) Dray, A. "Neuropharmacological Mechanisms of Capsaicin and Related Substances." //Biochemical Pharmacology// 44.4 (1992): 611-15. //ScienceDirect//. Sciverse, 8 Nov. 2002**b**. Web. 28 Nov. 2011. [|doi]
 * 7) Fitzgerald, M. "Capsaicin and Sensory Neurones — a Review." //Pain// 15.1-4 (1983): 109-30. //ScienceDirect//. Sciverse, 24 Mar. 2003. Web. 28 Nov. 2011. [|doi]
 * 8) Heyman, I., and H.P. Rang. "Depolarizing Responses to Capsaicin in a Subpopulation of Rat Dorsal Root Ganglion Cells." //Neuroscience Letters// 56.1 (1985): 69-75. //ScienceDirect//. Sciverse, 18 Mar. 2003. Web. 30 Nov. 2011. [|doi]
 * 9) Kirschstein, T., D. Büsselberg, and R. D. Treede. "Coexpression of Heat-evoked and Capsaicin-evoked Inward Currents in Acutely Dissociated Rat Dorsal Root Ganglion Neurons." //Neuroscience// 231.1 (1997): 33-36. //ScienceDirect//. Sciverse, 11 Sept. 1997. Web. 29 Nov. 2011. [|doi]
 * 10) Liu, L., Y. Wang, and S.a. Simon. "Capsaicin Activated Currents in Rat Dorsal Root Ganglion Cells." //Pain// 64.1 (1996): 191-95. //ScienceDirect//. Sciverse, 2 Mar. 1999. Web. 28 Nov. 2011. [|doi]
 * 11) Maggi, C. "Capsaicin and Primary Afferent Neurons: From Basic Science to Human Therapy?" //Journal of the Autonomic Nervous System// 33.1 (1991): 1-14. //ScienceDirect//. Sciverse, 14 Mar. 2003. Web. 28 Nov. 2011. [|doi]
 * 12) Marsh, S., C. Stansfeld, D. Brown, R. Davey, and D. Mccarthy. "The Mechanism of Action of Capsaicin on Sensory C-type Neurons and Their Axons in Vitro." //Neuroscience// 23.1 (1987): 275-89. //ScienceDirect//. Sciverse, 12 Mar. 2003. Web. 28 Nov. 2011. [|doi]
 * 13) Nagy, I., and H. Rang. "Noxious Heat Activates All Capsaicin-sensitive and Also a Sub-population of Capsaicin-insensitive Dorsal Root Ganglion Neurons." //Neuroscience// 88.4 (1999): 995-97. //ScienceDirect//. Sciverse, 15 Mar. 1999. Web. 29 Nov. 2011. [|doi]
 * 14) Nicholas, R. S., J. Winter, P. Wren, R. Bergmann, and C. J. Woolf. "Peripheral Inflammation Increases the Capsaicin Sensitivity of Dorsal Root Ganglion Neurons in a Nerve Growth Factor-dependent Manner." //Neuroscience// 91.4 (1999): 1425-433. //ScienceDirect//. Sciverse, 18 Oct. 1999. Web. 1 Dec. 2011. [|doi]
 * 15) Petersen, Marlen, and Robert H. LaMotte. "Relationships between Capsaicin Sensitivity of Mammalian Sensory Neurons, Cell Size and Type of Voltage Gated Ca-currents." //Brain Research// 561.1 (1991): 20-26. //ScienceDirect//. Sciverse, 11 Mar. 2003**a**. Web. 30 Nov. 2011. [|doi]
 * 16) Petersen, M., and R. Lamotte. "Effect of Protons on the Inward Current Evoked by Capsaicin in Isolated Dorsal Root Ganglion Cells." //Pain// 54.1 (1993): 37-42. //ScienceDirect//. Sciverse, 18 Mar. 2003**b**. Web. 29 Nov. 2011. [|doi]
 * 17) Priestley, J., S. Bramwell, L. Butcher, and A. Cuello. "Effect of Capsaicin on Neuropeptides in Areas of Termination of Primary Sensory Neurones." //Neurochemistry International// 4.1 (1982): 57-65. //ScienceDirect//. Sciverse, 7 Mar. 2003. Web. 27 Nov. 2011. [|doi]
 * 18) Ringkamp, Matthias, Yuan B. Peng, Gang Wu, Timothy V. Hartke, James N. Campbell, and Richard A. Meyer. "Capsaicin Responses in Heat-Sensitive and Heat-Insensitive A-Fiber Nociceptors." //The Journal of Neuroscience// 21.12 (2001): 4460-468. //The Journal of Neuroscience//. The Society for Neuroscience. Web. 30 Nov. 2011. [|doi]
 * 19) Savidge, J. R., S. P. Ranasinghe, and H. P. Rang. "Comparison of Intracellular Calcium Signals Evoked by Heat and Capsaicin in Cultured Rat Dorsal Root Ganglion Neurons and in a Cell Line Expressing the Rat Vanilloid Receptor, VR1." //Neuroscience// 101.1 (2001): 177-84. //ScienceDirect//. Sciverse, 20 Feb. 2001. Web. 28 Nov. 2011. [|doi]
 * 20) Wood, J. N., J. Winter, I. F. James, H. P. Rang, J. Yeats, and S. Bevan. "Capsaicin-induced Ion Fluxes in Dorsal Root Ganglion Cells in Culture." //The Journal of Neuroscience// 8.9 (1988): 3208-220. //The Journal of Neuroscience//. The Society for Neuroscience. Web. 29 Nov. 2011. [|doi]