Postnatal Development of KV Currents in Cultured Small Mouse Dorsal Root Ganglion (DRG) Neurons

Voltage-gated potassium (Kv) channels play an important role in the regulation of the electrophysiological properties of neurons. Neuronal excitability depends on the spatial and temporal expression of many different Kv subunits. Small dorsal root ganglion (DRG) neurons exhibit four different voltage-gated K+ currents: the M current (IM), the hyperpolarization-activated current (IH), the transient outward current (IA), and the delayed rectifier current (IK). It has been demonstrated that ∼60% of IK is carried by both homotetrameric Kv2.1 channels and heterotetrameric channels consisting of Kv2.1 and silent Kv subunits (i.e. Kv5-Kv6 and Kv8-Kv9) while Kv1.4, Kv3.4 and members of the Kv4 subfamily underlie IA. Little is known about the postnatal development of IK and IA and how these developmental changes influence the electrophysiological properties of small DRG neurons. Here we report a decrease of the stromatoxin (ScTx)-sensitive component of the whole-cell outward DRG current during postnatal development: the fraction of ScTx-sensitive current decreased from 64% to 51% between 1 month and 3 months old mice. ScTx is a gating modifier of both Kv4.2- and Kv2-containing channels and therefore this decrease could reflect a decrease in expression of one or more of these Kv subunits during development. However, the fraction of the anti-Kv2.1 antibody-sensitive current - which only reflects Kv2-containing channels - increased between 2 weeks and 2 months old mice from 32% to 42% of the whole-cell DRG current. These results together suggest that the decrease in the ScTx-sensitive component is due to a decrease in Kv4.2 expression. Furthermore, these results suggest that the balance between IA and IK and consequently the electrophysiological properties change during the postnatal development of small DRG neurons.(Supported by FWO fellowship to EB & grant FWO-G.0449.11N to DJS).