A feedback-controlled dynamic linear actuator to test foot withdrawal thresholds in rat

Abstract

We describe a method for evaluating the threshold for cutaneous mechanical sensation in rodents, based on a stimulator that drives a probe against the plantar surface of the foot. The stimulator applies loads that can be either constant or linearly increased. We describe withdrawal responses, including forms of movement that precede foot withdrawals. With constant stimuli, response latency declines in a nonlinear fashion as stimulus magnitude is increased. With ramped stimuli the effect of loading rate is complex, reflecting both the rate of change of the stimulus and the animal\u27s reaction time. We demonstrate the utility of using ramped stimuli in experiments that show that thresholds vary spatially across the foot and experiments that show that intradermal capsaicin injections cause allodynia but not hyperalgesia

Learned Avoidance From Noxious Mechanical Simulation But Not Threshold Semmes Weinstein Filament Stimulation After Nerve Injury in Rats

“…However, problems of tip geometry, force generation, inconsistency in use, and experimenter bias suggest that monofilament stimulators are not ideal for quantitative sensory testing 3. It has also been shown that withdrawal threshold measurement is complex and depends on the various parameters of the stimulus profile, therefore complicating the concept of threshold 11. The key finding of our study is the aversiveness of nociceptive stimulation when it is accompanied by a complex, sustained hyperalgesia response.…”

Development of a mechanical stimulator and force measurement system for the assessment of nociceptive thresholds in pigs

“…For this reason it was decided to measure force thresholds (peak force before withdrawal of the foot from a linearly increasing load) rather than response latency to a fixed intensity noxious stimulus, as it was reasoned that this parameter is less affected by differences in posture and therefore possible effects on limb load bearing and muscle contractility. In addition, with fixed intensity stimuli, response latencies decline in a nonlinear fashion as the stimulus magnitude is increased (Grigg et al, 2007).…”

“…Bias is introduced because it is the experimenter who determines the load rate and duration of stimulus application, and subjectively determines what constitutes a withdrawal (Grigg et al, 2007). In this study the load rate and trial duration were pre-programmed and the withdrawal response was objectively determined independent of the experimenter, thus reducing observer bias.…”

Noradrenergic neurons in the locus coeruleus contribute to neuropathic pain

“…Tactile allodynia was also assessed with a machine-mounted probe (MMP) (Dynamic Plantar Aesthesiometer™; Ugo Basile Inc, Comerio VA, Italy) (Gibbs et al, 2006, Grigg et al, 2007). This method provides a parametric alternative to the use of von Frey hairs for the assessment of mechanical allodynia.…”