Melting Away Pain: Decay of Thermal Nociceptor Transduction during Heat-Induced Irreversible Desensitization of Ion Channels

Thermal transient receptor potential channels play a key role in thermal sensation. Although predictive models exist for temperature-dependent transduction through these channels and for the associated sensations of pain, the ability to predict irreversible desensitization has been lacking. We explored the role of irreversible ion channel desensitization in pain sensation and hypothesized that desensitization of ion channels would follow the kinetics similar to the denaturation of catalytic enzymes. We therefore proposed a three-state model to simulate the kinetic of temperature-sensitive ion channels from the closed state through opening and irreversible thermal desensitization. We tested the model against data obtained in vivo from a feline model. The theoretical model predicts all experimental data with reasonable accuracy, and represents an important step toward the ability for understanding of the molecular basis of nociceptor signaling providing the possibility to design local anesthesia regimens and to the prediction of postoperative pain.