Figure 1.
Effect of metformin on cisplatin- or paclitaxel-induced mechanical allodynia in mice.
A). Treatment schedule; X: injection; O: no treatment. B) Mice (n = 10–12/group) were treated with cisplatin (cumulative dose 23 mg/kg i.p.) and metformin (200 mg/kg/dose i.p.) as depicted in panel A. Mechanical allodynia was quantified with von Frey hairs using the up and down method. C). Effect of delayed metformin treatment on cisplatin-induced mechanical allodynia. Mice (n = 8/group) received i.p. injections with cisplatin (cumulative dose 23 mg/kg i.p.) and delayed metformin (200 mg/kg/dose i.p.) as depicted in panel A and mechanical allodynia was monitored. D). Mice (n = 4–7/group) were treated with paclitaxel (10 mg/kg/every other day, i.p. for two weeks) and metformin (200 mg/kg i.p. daily from one day before until one day after paclitaxel) and mechanical allodynia was measured. E). Change in body weight after cisplatin and metformin treatment. ** p<0.01 vs. Saline+Saline group; ## p<0.01 vs. Saline+Cisplatin; && p<0.01 vs. Saline+Paclitaxel.
Figure 2.
Effect of metformin treatment on cisplatin-induced sensory deficits.
A). Mice (n = 6–10/group) were treated with cisplatin and metformin as described in Figure 1. The time to respond to an adhesive patch on the hind paw was monitored. B). Effect of delayed metformin on cisplatin induced sensory deficits (n = 7–8/group). C). Effect of cisplatin treatment on rotarod performance. Mice (n = 6/group) were treated with cisplatin and their performance on the rotarod was monitored as an index of motor coordination. E). Mice (n = 7/group) were treated with lidocaine (5 µL, 4% in saline) or saline and 10 mins. later, the time to respond to an adhesive patch on the hind paw was measured. * p<0.05, ** p<0.01 vs. Saline+Saline; # p<0.05 vs. Saline+Cisplatin.
Figure 3.
Effect of metformin on loss of intraepidermal nerve fibers induced by cisplatin.
Mice (n = 4–6 per group) were treated with cisplatin and metformin as in figure 1. Paw biopsies obtained from the hind paw at 5 weeks after the start of treatment were stained for intraepidermal nerve fibers (PGP9.5; red) and collagen (green). (A) saline/saline; (B) saline/cisplatin; (C) metformin/cisplatin. White arrows indicate the intraepidermal nerve fibers stained by PGP9.5 (in red), which can clearly be seen crossing the basement membrane (in green) and extending as long lines into the epidermis. (D) Quantification of intraepidermal nerve fiber density. ** p<0.01 vs. Saline+Saline; ## p<0.01 vs. Saline+Cisplatin.