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 N(2) 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±0.3 mmol l(-1). The total [K(+)](o) baseline variation (Δ[K(+)](o)) was stabilized at 17°C (-1.1±1.3 mmol l(-1)), mildly rose at 23°C (17.3±1.4 mmol l(-1)), and considerably increased at 29°C (332.7±83.0 mmol l(-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 O(2) reperfusion with possible application for therapeutic treatment of stroke or heart attack.