Differential expression of alpha-adrenoceptor subtypes in rat dorsal root ganglion after chronic constriction injury

Abstract

mRNAs of alpha-adrenoceptor (α-AR) subtypes are found in neurons in dorsal root ganglion (DRG) and change after peripheral nerve injury. In this study, the distribution of α-AR subtype proteins was studied in L₅ DRG of normal rats and rats with chronic constriction injury of sciatic nerve (CCI). Using immunofluorescence technique, it was found that α_1A-, α_1B-, and α_2A-AR proteins were expressed in large, medium, and small size neurons in normal DRG, and significantly increased in all size neurons 14 days after CCI. α_1D- and α_2C-AR was also expressed in all size neurons in normal DRG. However, α_1D-AR was significantly increased and α_2C-AR was decreased in small size neurons 14 days post CCI. α_2B-AR neurons were not detectable in normal and CCI DRG. Co-expression of α_1A- and α_2A-AR in the same neuron was observed in normal DRG and increased post CCI. Collectively, these results indicated that there is distinct distribution of α-AR subtypes in DRG neurons, and the distribution and levels of expression of α-AR subtypes change differently after CCI. The up-regulation of α-AR subtypes in DRG neurons may play an important role in the process of generating and transmitting neuropathic pain.

Keywords

alpha-adrenoceptor / chronic constriction injury / dorsal root ganglion / neuropathic pain / noradrenaline

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