Developmental temperature selectively regulates a voltage-activated potassium current in Drosophila

Ionic currents are regulated by many conditions including disease states, ageing, learning and memory, and chronic drug treatment. Here we describe a novel phenomenon of regulation of ionic currents by developmental temperature. Raising Drosophila larvae at 28°C instead of 18°C increased one of the two voltage-activated K⁺- currents, the delayed sustained I_K, in their muscles by up to 3.5-fold, with little effect on the early transient current, I_A. Consistent with this increase in I_K, the amplitude and the duration of the action potentials were reduced. The major increase in I_K occurred between a rather abrupt interval from 25° to 28°C. The activation curve of the increased current was shifted towards hyperpolarizing potentials. There was no change in activation kinetics. This phenomenon has mechanistic implications for activity-dependent neuronal plasticity, expression of ion channels in cultured cells and heterologus systems, phototransduction, and behavior. The specificity of the regulation suggests a discrete mechanism geared to affect excitability such that it can respond to altered external stimuli such as temperature. 1994 John Wiley & Sons, Inc.