Changes in expression of voltage-gated potassium channels in dorsal root ganglion neurons following axotomy

Several families of voltage-gated potassium channels (Kv), including a spectrum of subtypes, are involved in regulating and modifying the integration and transmission of electrical signals in the nervous system. However, the specific patterns of Kv expression in normal or injured dorsal root ganglion (DRG) neurons have not been studied. Previous studies have examined the expression of voltage-gated sodium channels in DRG neurons, and also the selective up- and downregulation of several of these channels following axonal injury to the DRG neurons. In the present study, we used immunocytochemical methods to investigate the expression of Kv channels (Kv1.1, 1.2, 1.3, 1.4, 1.5, 1.6, and 2.1) in DRG cells cultured from control and axotomized adult rats. Kv1.2 and 2.1 immunoreactivity in DRG neurons showed large decreases following axotomy, whereas Kv1.1 and 1.3 showed smaller decreases. Kv1.4 and 1.6 immunostaining were not altered by axotomy, and Kv1.5 immunoreactivity was low in both control and axotomized DRG neurons. These results provide molecular correlates for the expression of multiple K+ currents in normal DRG neurons and indicate that, in relation to changes in sodium channel expression, there are decreases in specific potassium channels following axotomy in these cells. The alterations in K+ and Na+ channel expression following axonal injury may lead to changes in electrical excitability of the DRG neurons, and might contribute to chronic pain syndromes.