Olfactory receptor axons influence the development of glial potassium currents in the antennal lobe of the moth Manduca sexta

In the olfactory (antennal) lobe of the moth Manduca. sexta, olfactory rece ptor axons strongly influence the distribution and morphology of glial cell s. In the present study, we asked whether the development of the electrophy siological properties of the glial cells is influenced by the receptor axon s. Whole-cell currents were measured in antennal lobe glial cells in acute brain slices prepared from animals at different stages of metamorphic devel opment (stages 3, 6, and 12). Outward currents were induced by depolarizing voltage steps from a holding potential of -70 mV. At all developmental sta ges investigated, the outward currents were partly blocked by bath applicat ion of the potassium channel blocker 4-aminopyridine (4AP, 10 mM) or by inc luding tetraethylammonium (TEA, 30 mM) in the pipette solution. The relativ e contribution of the 4AP-sensitive current to the outward current increase d from 18% at stages 3 and 6 to 42% at stage 12, while the TEA-sensitive cu rrent increased from 18% at stage 3 to 81% at stage 6, and then declined ag ain to 40% at stage 12. In contrast, in the absence of receptor axons, thes e changes in the contribution of the TEA- and 4AP-sensitive currents to the total outward current did not occur; rather, the current profile remained in the most immature state (stage 3). The results suggest that olfactory re ceptor axons are essential for development of the mature pattern of glial p otassium currents. (C) 2001 Wiley-Liss, Inc.