DEVELOPMENTAL TEMPERATURE SELECTIVELY REGULATES A VOLTAGE-ACTIVATED POTASSIUM CURRENT IN DROSOPHILA

Ionic currents are regulated by many conditions including disease states, aging, 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 degrees C instead of 18 degrees 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 degrees C to 28 degrees 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 heterologous 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. (C) 1994 John Wiley and Sons, Inc.