Protective effect of hypothermia on brain potassium homeostasis during repetitive anoxia in Drosophila melanogaster

Abstract

Oxygen deprivation in nervous tissue depolarizes cell membranes, increasing extracellular potassium concentration ([K+]o). Thus, [K+]o can be used to assess neural failure. The effect of temperature (17, 23 or 29°C) on the maintenance of brain [K +]o homeostasis in male Drosophila melanogaster (w1118) individuals was assessed during repeated anoxic comas induced by N2 gas. Brain [K+]o was continuously monitored using K +-sensitive microelectrodes while body temperature was changed using a thermoelectric cooler (TEC). Repetitive anoxia resulted in a loss of the ability to maintain [K+]o baseline at 6.6±0.3mmol I-1. The total [K+]o baseline variation (δ[K+]o) was stabilized at 17°C (-1.1±1.3mmol I-1), mildly rose at 23°C (17.3±1.4mmol I-1), and considerably increased at 29°C (332.7±83.0mmol I-1). We conclude that (1) reperfusion patterns consisting of long anoxia, short normoxia and high cycle frequency increase disruption of brain [K+]o baseline maintenance, and (2) hypothermia has a protective effect on brain K+ homeostasis during repetitive anoxia. Male flies are suggested as a useful model for examining deleterious consequences of O2 reperfusion with possible application for therapeutic treatment of stroke or heart attack. © 2012. Published by The Company of Biologists Ltd.