Fig. 1. PV and SOM neurons in the TRN differentially regulate nociceptive behaviors. (A) Description of experimental procedures. PV-Cre or SOM-Cre mice either expressed ChR2 or eYFP (control) in the right TRN. Two weeks later mechanical threshold changes induced by the right TRN blue light stimulation were measured. Subsequent behavioral tests (the Hargreaves and the formalin test) were carried out at 2 week intervals. (B) Representative images of ChR2 expression in the TRN of PV-Cre and SOM-Cre mice. White dashed lines mark the site of an optic fiber implant. Thinner light gray dotted line outlines divisions of the TRN. Drawing on the right shows divisions of the TRN according to Clemente-Perez et al. (2017). (C) Mechanical threshold changes due to blue light stimulation of the right TRN measured with the von Frey test. (D) Acute heat nociception changes of the plantar paw due to blue light stimulation of the right TRN. (E) Inflammatory nociceptive behavior induced by formalin injection. Repeated measures ANOVA with Games-Howell post hoc was used to assess the differences between groups over time. Horizontal blue lines indicate when blue light stimulation was delivered. (C~E) All data represent mean±SEM. Kruskal-Wallis test followed by the Mann-Whitney U test, was used to test statistical significance between groups, *p<0.05, **p<0.01, ***p<0.001.
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