Skip to main content
. Author manuscript; available in PMC: 2016 Aug 4.
Published in final edited form as: Nat Neurosci. 2013 Jan 6;16(2):183–192. doi: 10.1038/nn.3295

Figure 5. P2X4Rs in microglia are required for morphine-induced hyperalgesia.

Figure 5

a. Rat mechanical pain threshold 5 h after intrathecal injections of cultured microglia treated with morphine (100 nM, n = 7; H: 19.98, **P < 0.01), morphine+TNP-ATP (n = 5, *P > 0.05), morphine+PPADS (n = 8; **P < 0.01), vs CTR (n = 7). b–d. Lack of hyperalgesia in P2rx4−/−mice: b. Thermal (n = 5 mice per group) and mechanical (n = 7 mice per group) pain threshold after 5 days of subcutaneous morphine injections in P2rx4+/+ mice vs P2rx4−/− mice (U: 5 for mechanical and U: 2 for thermal test, *P < 0.05). c. Licking time following mechanical stimulation of the paw (morphine-treated P2rx4+/+ vs morphine-treated P2rx4−/−, *P < 0.05; # significant differences compared to the baseline); d. Vocalizations produced by subcutaneous injections (morphine-treated P2rx4+/+ vs other groups, *P < 0.05; # significant differences compared to the baseline). e–g. Effect of intrathecal TNP-ATP (30 nmol) on MIH in rats: e. thermal pain threshold prior to morphine injection in vehicle (n = 8) vs TNP-ATP injected rats (n= 8; day 7, U: 13, *P < 0.05); f. thermal pain threshold 1 h after morphine. g. Mechanical withdrawal threshold following TNP-ATP in morphine-treated rats measured prior to morphine injection (day 7, CTR, n = 6, TNP-ATP, n = 7; U: 0, **P < 0.01). h. X-gal staining in P2rx4−/−mice (scale bar, 30 μm). The percentage SDH staining area of control (3.6 ± 0.3%, n = 5 sections) and morphine-treated mice (4.8 ± 0.3%, n=12 sections; U: 10, *P < 0.05). i–j. Increased expression and function of P2X4R in morphine-treated (100 nM) microglia cultures: i. Expression of P2X4R after morphine treatment normalized to the saline controls for 1 day (d1, n = 7 trials), 3 days (d3, n = 7) and 5 days (d5, n = 7; H: 19.35, ***P < 0.001); j. ATP-mediated currents in morphine-treated microglia over 5 days (peak current normalized to the pre-ATP baseline: 1.6 ± 0.2; n = 12 cells; U: 91, *P < 0.05) vs control (1.0 ± 0.1; n = 28 cells). All threshold values in the figure are normalized to the baseline. Abb.: PWT = paw withdrawal threshold; CTR = control; MS = morphine sulphate; a.u. = arbitrary unit; X-gal = 5-bromo-4-chloro-indolyl-galactopyranoside; error bars = s.e.m.