Validation of the digital pressure application measurement (PAM) device for detection of primary mechanical hyperalgesia in rat and mouse antigen-induced knee joint arthritis

Abstract

Several tests have been developed to obtain mechanical nociceptive withdrawal thresholds for arthritis-associated pain research in preclinical animal models, which are routinely used for testing the efficacy of antinociceptive pharmaceutical candidates. Here, we aimed to validate a recently introduced and commercially available digital pressure application measurement (PAM) device for the detection of primary mechanical hyperalgesia in a model of antigen-induced knee joint arthritis (AIA) in rats and mice. Two particular advantages of the PAM device are visual feedback control of the force increase rate and the detection of the complete threshold range. Using PAM, we were able to quantify mechanical thresholds at the knee joint in rats and mice (400 and 350 g, respectively) before and during the time course of AIA (approximately 100 g for rats and mice in the acute phase). Inter-observer agreement was generally higher when using PAM instead of an analog dynamometer. In conclusion, the digital PAM device is a suitable apparatus to detect primary mechanical hyperalgesia in experimental knee joint arthritis in rats and mice. The use of this device allows visual feedback control of the stimulus rate, thus minimizing the chances of confounding factors arising from differences in ramp speed.