Phosphorylation of ERK1/2 in Dorsal Root Ganglia following Sequential Mustard Oil and Thermal Stimulation of the Rat Hind Paw

Abstract

The effect of a sequential stimulation by mustard oil and noxious heat or cold on the phosphorylation of ERK1/2 in sensory afferents was investigated. The stimuli were applied to the rat hind paw and phospho-ERK1/2 (p-ERK1/2) was measured by fluorescence-immunohistochemistry in the lumbar dorsal root ganglia (DRGs) neurons. All stimuli lead to a significant increase in the number of small size DRG cells displaying cytoplasmic staining for p-ERK1/2. The combination of mustard oil with cold significantly increased the number of cells with cytoplasmic staining above the level obtained with cold stimulus alone, however this was not observed with the combination of mustard oil and heat. Nuclear staining was weak and was found increased by mustard oil combined with cold stimulation. Mustard oil is known to activate TRPA1 and TRPV1 channels, heat TRPV1, and cold TRPA1 and TRPM8. The present findings shed new light on the DRG cell populations reacting with cytoplasmic and nuclear staining for p-ERK1/2 following sequential irritant chemical and thermal stimuli to the skin.