Hannah Goodings’ MSc Thesis Proposal

Title: “Secondary Hyperalgesia Following Prolonged Low-Dosage Capsaicin Exposure”

Thesis Supervisor: Dr. John Kramer
Committee Members: Dr. Brain Cairns, Dr. Jean-Sebastian Blouin

Background: Capsaicin, the active ingredient in chili peppers, is a common ingredient in pain relieving ointments. The mechanism of pain relief, resulting from prolonged use of low concentration (0.1%), is currently missing from the literature. Objective: Determine the effect of adjacent sensitization on a region of skin desensitized via the application of capsaicin, known to activate TRPV1 (Transient Receptor Potential cation channel subfamily V member 1) receptors on peripheral afferent neurons. Methods: Individuals will follow a 21-day protocol of applying 0.1% capsaicin cream on the proximal forearm. Following 19-days of capsaicin application, Contact Heat Evoked Potentials (CHEPS) will be collected in the area of application and an adjacent control region. Mechanical pain thresholds and dynamic mechanical allodynia will be assessed within the capsaicin and control regions prior to, and following, a repeated suprathreshold heat stimulus applied between the two regions. Hypothesis: The 19-day application period of low concentration capsaicin will be sufficient to desensitize TRPV1 receptors and the desensitized region will not be susceptible to secondary hyperalgesia symptoms following an adjacent suprathreshold stimuli. Significance: Findings from this thesis will further inform our mechanistic understanding of sensitization, an underlying mechanism in chronic pain.