Downregulation of voltage-gated potassium channel α gene expression in dorsal root ganglia following chronic constriction injury of the rat sciatic nerve

The hyperexcitability and ectopic spontaneous discharge (ESD) of primary sensory neurons may be important for the generation or maintenance of neuropathic pain. To investigate the relationship between the electrical abnormalities of injured neurons and voltage-gated potassium (Kv) channel gene expression, the expression of the Kv channel α genes in the dorsal root ganglion (DRG) was monitored by reverse transcription-polymerase chain reaction (RT-PCR) in a chronic constriction injury (CCI) model of neuropathic pain. Electrophoresis of the RT-PCR products showed the presence of several Kv α transcript types with various levels of basal expression in lumbar 4, 5, and 6 DRGs. The Kv 1.2, 1.4, 2.2, 4.2, and 4.3 mRNA levels in the ipsilateral DRG were 63-73% of the contralateral sides of the same animal at 3 days and 34-63% at 7 days following CCI. In addition, Kv 1.1 mRNA levels declined to about 72% of the contralateral level at 7 days. No significant changes in Kv 1.5, 1.6, 2.1, 3.1, 3.2, 3.5, and 4.1 mRNA levels were detectable in the ipsilateral DRG at both days. These results suggest that the downregulation of Kv channel α gene expression in the DRG following CCI may result in the reduction of K⁺ current and contribute to neuronal excitability and ESD generation.