Fig. 3

Procyanidins attenuated chronic morphine tolerance by inhibiting the neuron-glia pathway in the spinal cord. a Procyanidins inhibited the morphine-induced upregulation of phosphorylated PKC and phosphorylated NMDAR-NR1 in the spinal cord. The western blot samples (n = 4) were collected 2 h after the last morphine treatment. b Procyanidins inhibited the morphine-induced phosphorylation of JNK and ERK in the spinal cord. The western blot samples (n = 4) were collected as above. c, d Confocal images and immunofluorescence analysis showed the activation of neuronal c-fos and CGRP after morphine treatment (n = 4) in the spinal cord. The quantification of c-fos and CGRP immunofluorescence was respectively represented as number of c-fos positive cells and mean fluorescence pixels in the superficial dorsal horns. *p < 0.05, **p < 0.01, ***p < 0.001 vs. baseline; ^# p < 0.05, ^## p < 0.01, ^### p < 0.001 vs. morphine-treated group. Scale bar 75 μm