title: Muscle membrane potential and insect chill coma.
abstract: Chill-susceptible insects enter a reversible paralytic state, termed chill coma, at mild low temperatures. Chill coma is caused by neuromuscular impairment, allegedly triggered by cold-induced depolarization of muscle resting membrane potential (Vm). We used five Drosophila species that vary in cold tolerance (chill coma temperature spanning ∼11°C) and repeatedly measured muscle Vm during a downward temperature ramp (20 to -3°C). Cold-tolerant species were able to defend their Vm down to lower temperatures, which is not explained by species-specific differences in initial Vm at 20°C, but by cold-tolerant drosophilids defending Vm across a broad range of temperatures. We found support for a previously suggested 'critical threshold' of Vm, related to chill coma, in three of the five species. Interestingly, the cold-tolerant Drosophila species may enter coma as a result of processes unrelated to muscle depolarization as their Vm was not significantly depolarized at their chill coma temperatures.
authors.affiliation: Department of Zoophysiology, Faculty of Science and Technology, Aarhus University, Aarhus DK-8000, Denmark jonas.andersen@bios.au.dk.
authors.forename: Jonas L
authors.initials: JL
authors.lastname: Andersen
authors.affiliation: Department of Zoophysiology, Faculty of Science and Technology, Aarhus University, Aarhus DK-8000, Denmark.
authors.forename: Heath A
authors.initials: HA
authors.lastname: MacMillan
authors.affiliation: Department of Zoophysiology, Faculty of Science and Technology, Aarhus University, Aarhus DK-8000, Denmark.
authors.forename: Johannes
authors.initials: J
authors.lastname: Overgaard
mesh_terms: D000818:Animals; D003080:Cold Temperature; D004330:Drosophila / Q000502:physiology*; D008564:Membrane Potentials; D018482:Muscle, Skeletal / Q000502:physiology; D013045:Species Specificity
keywords: Chill tolerance; Cold exposure; Comparative; Critical thermal minimum; Inter-species