Abstract
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 IK, in their muscles by up to 3.5-fold, with little effect on the early transient current, IA. Consistent with this increase in IK, the amplitude and the duration of the action potentials were reduced. The major increase in IK occurred between a rather abrupt interval from 25 degrees 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.
