Shaw-like potassium currents in the auditory rhombencephalon throughout embryogenesis

The Shaw subfamily of potassium channel genes, including Kv3.1, are highly expressed within the auditory nuclei of the brainstem, where they have been implicated in the characteristic response properties of particular types o f neurons, Potassium currents carried by Kv3.1 are voltage-dependent, have a high activation threshold, are slow to inactivate, and are very sensitive to 4-aminopyridine (4-AP) and tetraethylammonium (TEA), We have investigat ed the developmental appearance of potassium currents in cell cultures from nucleus magnocellularis and its precursor neuroblasts from the acoustico-v estibular anlage of the chicken, Whole-cell patch recordings revealed that high-threshold, sustained, outward currents were present in 91% of neurobla sts. These currents displayed high sensitivities to TEA and 4-AP. The remai ning 9% of neuroblasts exhibited only transient outward currents, Most cell s (74%) had both a sustained and an initial transient component of outward current, These current types were observed throughout embryogenesis, beginn ing with the earliest ages (embryonic day [E]2), During proliferation and m igration, and early neuronal differentiation, current levels were low; they incremented gradually during the time when the first synapses occur on den drites and increased 2- to 3-fold just before hatching, when axosomatic syn apses form. These findings suggest that the Shaw subfamily of channels in n ucleus magnocellularis may be involved in early neuronal development, as we ll as in synaptic function later on. J. Neurosci. Res. 58:791-804, 1999, (C ) 1999 Wiley-Liss, Inc.