Pain in rodents is often inferred from their withdrawal from noxious stimuli. Threshold stimulus intensity or response latency is used to quantify pain sensitivity. This usually involves applying stimuli by hand and measuring responses by eye, which limits reproducibility and throughput. We describe a device that standardizes and automates pain testing by providing computer-controlled aiming, stimulation, and response measurement. Optogenetic and thermal stimuli are applied using blue and infrared light, respectively. Precise mechanical stimulation is also demonstrated. Reflectance of red light is used to measure…

In this issue of Cell Reports Methods, Dedek et al. present RAMalgo—an AI-powered, automated platform for quantifying nociceptive behaviors in mice. With integrated video tracking and mechanical, thermal, and optogenetic stimulation, RAMalgo has the potential to increase standardization and throughput of pain behavior measurement in rodents.

Optogenetics provides an unprecedented opportunity to delineate how different somatosensory afferents contribute to sensation, including pain. By expressing channelrhodopsin-2 (ChR2) in certain afferents, those afferents can be selectively activated by transcutaneous photostimuli applied to behaving mice. Despite the great care taken to precisely target expression of ChR2, imprecise photostimulation has hindered quantitative behavioral…