Optimization of capsaicin-induced dermal blood flow measurement by laser Doppler imaging in cynomolgus macaque.

BACKGROUND Capsaicin is used in several areas of non-human primate research including allodynia and dermal blood flow (DBF). The capsaicin-induced DBF increase was measured using laser Doppler imaging (LDI), but this response is known to diminish upon repeated topical applications. Refinement of the experimental procedures could improve the rigor and reproducibility of the DBF migraine model. METHODS Optimal anatomical site in cynomolgus was determined, and conditions and experimental settings for DBF measurement using LDI were established. Then, two study design trial structures were compared. RESULTS Medial thigh was the preferrable site, and an ethanol-Tween 20 formulation of capsaicin was desirable. A 1-week washout for contralateral side or 2-week washout for ipsilateral side was necessary to eradicate capsaicin desensitization. CONCLUSIONS With the established technicality in DBF measurements in cynomolgus macaques, the capsaicin-induced DBF model may be utilized in translational medical research in developing migraine therapeutics.