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Updated: Aug 30, 2026
Intracerebroventricular Treatment with Resiniferatoxin and Pain Tests in Mice
Published on: September 2, 2020
Resiniferatoxin-induced loss of plasma membrane in vanilloid receptor expressing cells
Robert M Caudle1, Laszlo Karai, Narasaiah Mena
1Department of Oral and Maxillofacial Surgery, University of Florida College of Dentistry and the University of Florida McKnight Brain Institute, 1600 Archer Road, P.O. Box 100416, Gainesville, FL 32610, USA. rcaudle@dental.ufl.edu
Abstract:
Resiniferatoxin (RTX), a potent analog of capsaicin, was evaluated electrophysiologically in dorsal root ganglion (DRG) cells and cell lines ectopically expressing the vanilloid receptor type 1 (VR1) to determine if cell phenotype influenced RTXs neurotoxic properties. Furthermore, capsaicin and heat activation of VR1 were evaluated in these cells to determine if cellular damage was unique to RTX activation of the receptors. RTX application to DRG cells identified as type 1, 2 or 5, cell types known to express VR1, induced large inward currents. RTX did not induce currents in DRG cells that do not express the receptor (type 4 cells). In cell lines ectopically expressing VR1, RTX-induced similar currents. RTX produced no effect in non-transfected cells. After exposure to RTX both DRG cells and transfected cells failed to respond to subsequent applications of the agonist. In addition, whole cell capacitance was reduced up to 70%. The decrease in capacitance was associated with the loss of plasma membrane, as determined by confocal microscopy. Cell phenotype, other than VR1 expression, did not influence the response to RTX. Interestingly, capsaicin and heat activation of vanilloid receptors also decreased cell capacitance, but the loss of membrane was not as great as with RTX and responses to these stimuli were not lost after the initial exposure. The loss of cell membrane required elevated intracellular levels of Ca2+. From these data it was concluded that the loss of cell membrane was dependent on the presence of both VR1 and intracellular Ca2+ accumulation, but not on cell phenotype.
Insights
Resiniferatoxin (RTX) causes neurotoxicity by activating vanilloid receptor type 1 (VR1), leading to cell membrane loss. This effect, dependent on VR1 and calcium, is not influenced by cell type.
Area of Science:
- Neuroscience
- Molecular Biology
- Cell Biology
Background:
- Resiniferatoxin (RTX) is a potent capsaicin analog known to activate the vanilloid receptor type 1 (VR1).
- The neurotoxic properties of RTX and its effects on VR1 activation require further investigation, particularly concerning cell phenotype influence.
Purpose of the Study:
- To determine if cell phenotype influences the neurotoxic properties of Resiniferatoxin (RTX).
- To compare the effects of RTX, capsaicin, and heat on vanilloid receptor type 1 (VR1) activation and subsequent cellular damage.
Main Methods:
- Electrophysiological evaluation of RTX, capsaicin, and heat activation of VR1 in dorsal root ganglion (DRG) cells and VR1-expressing cell lines.
- Confocal microscopy was used to assess plasma membrane integrity and loss.
- Intracellular calcium levels were monitored to understand their role in RTX-induced cell damage.
Main Results:
- RTX application induced large inward currents in VR1-expressing DRG cells and transfected cell lines, but not in non-transfected cells or VR1-negative DRG cells.
- Following RTX exposure, cells lost responsiveness to subsequent agonist application, and whole-cell capacitance decreased up to 70% due to plasma membrane loss.
- Capsaicin and heat also decreased cell capacitance, but to a lesser extent than RTX, and did not abolish subsequent responses. Membrane loss was dependent on elevated intracellular Ca2+.
Conclusions:
- Cell phenotype does not influence RTX-induced neurotoxicity, other than VR1 expression.
- RTX-induced cell membrane loss is dependent on the presence of VR1 and intracellular calcium accumulation.
- While capsaicin and heat also activate VR1 and cause some membrane loss, RTX elicits a more severe and persistent neurotoxic effect.
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