Nociceptive activity-driven, PKG-I-dependent phosphorylation of myosin light chains (MLC) in DRG in vivo and its contribution to synaptic potentiation at contacts between C-nociceptors and spinal-PAG projection neurons.

<p>(A, B) A typical example (A) and quantitative summary (B) of levels of phosphorylated MLC in L4-L5 DRGs of SNS-PKG-I^−/− mice and PKG-I^fl/fl littermates in the naïve state or following formalin injection in the hindpaws. (C) Formalin-induced increase in MLC phosphorylation in L4-L5 DRGs is reduced in wild type mice treated with inhibitors of cGMP synthesis, ODQ (25 mg/kg body weight), and LY83583 (12.5 mg/kg body weight). Mean values from three experiments are depicted below the representative Western blot. (D) Photomicrographic images showing an increase in immunoreactivity for phosphorylated myosin light chains in the spinal dorsal horns in wild-type mice following injection of formalin in the hindpaw. Note increased staining in superficial neuropil as well as cell bodies. Scale bars = 100 µm. (E, F) Time-course (E) and quantitative summary at 30 min (F) after the conditioning stimulus of the blockade of spinal synaptic potentiation by ML-7, an inhibitor of myosin light chain kinase (MLCK) (<i>n</i> = 8 slices/group). (G) MLCK blockade does not significantly affect basal transmission upon dorsal root stimulation (3 mA).