Evoked and spontaneous pain assessment during tooth pulp injury

Abstract

Injury of the tooth pulp is excruciatingly painful and yet the receptors and neural circuit mechanisms that transmit this form of pain remain poorly defined in both the clinic and preclinical rodent models. Easily quantifiable behavioral assessment in the rodent orofacial area remains a major bottleneck in uncovering molecular mechanisms that govern inflammatory pain in the tooth. Here we use a dental pulp injury model in the mouse and expose the tooth pulp to the outside environment, a procedure we have previously shown produces pulpal inflammation. We demonstrate here with RNAscope technology in the trigeminal ganglion of injured mice, an upregulation of genes that contribute to the inflammatory pain state. Using both evoked and spontaneous measures of pain in the orofacial area, including application of von Frey Hair filaments and pain feature detection with the mouse grimace scale, we reveal a differential timeline of induction of spontaneous pain versus mechanical allodynia following pulpal injury. This work demonstrates that tooth pain can be easily assessed in freely behaving mice using approaches common for other types of pain assessment. Harnessing these assays in the orofacial area during gene manipulation should assist in uncovering mechanisms for tooth pulp inflammation and other forms of trigeminal pain. 11, eaal2171,

Chronic paternal morphine exposure increases sensitivity to morphine-derived antinociception

“…For example, several elegant recent studies required a long training period (4-14 days) for semirestrained and water deprived mice to self-report a sensory stimulus to the paw with a water reward, as a top-down indicator of the animal's sensory state (Neubarth et al, 2020;Paricio-Montesinos et al, 2020). The grimace scales for mice and rats that focus on eye and facial features offer advantages, but they are also labor-intensive and not conducive for high-throughput analyses across all rodents of differing coat colors (Langford et al, 2010;Rossi et al, 2020;Sotocinal et al, 2011). To address the question of mechanical nociception in rats in the context of multigenerational morphine exposure, an ideal platform would allow an experimenter to rapidly test unrestrained rodents and produce easily quantifiable readouts.…”