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. Author manuscript; available in PMC: 2023 Mar 1.
Published in final edited form as: Pain. 2022 Mar 1;163(3):508–517. doi: 10.1097/j.pain.0000000000002376

FIGURE 2. Microglial ablation in DTR transgenic mice did not affect the expression and maintenance of mechanical OIH.

FIGURE 2.

A. Effect of early DT administration on mechanical sensitivity of WT and CD11b-DTR transgenic mice with or without morphine (Mor) treatment. Von Frey tests were performed to measure the hind paw withdrawal threshold (PWT). Von Frey testing was performed 2 hours prior to morphine (i.p. daily for 4 days, indicated by the red bar) and DT (i.t.; indicated by blue arrows) treatment, to avoid the interference of potential acute analgesic effects of morphine administration. DT treatment of the DTR transgenic mice (red triangle) did not cause detectable effect on the expression of morphine-induced hypersensitivity compared with the OIH profiles of various control groups, including morphine-treated WT (red triangle) and DTR transgenic mice without DT (green square). N=6 mice/group; p>0.05 (DTR+DT+Mor vs. DTR+Mor, DTR+DT+Mor vs. WT+DT+Mor, or DTR+DT+Mor vs. WT+Mor); B. Effect of late DT administration on mechanical sensitivity of WT and CD11b-DTR transgenic mice with morphine (Mor) treatment. DT was injected (i.t.; indicated by blue arrows) after the completion of morphine administration (i.p. daily for 4 days, indicated by the red bar) to evaluate the role of microglia in OIH maintenance. No detectable effects on mechanical sensitivity were observed for DT-treated DTR transgenic mice (empty red square), compared with various control groups. N=6 animals/group; p>0.05 (DTR+DT+Mor vs. DTR+Mor, DTR+DT+Mor vs. WT+DT+Mor, or DTR+DT+Mor vs. WT+Mor).