Abstract
ABSTRACTEctothermic animals in areas characterised by seasonal changes are susceptible to extreme fluctuations in temperature. To survive through varied temperatures, ectotherms have developed unique strategies. This study focuses on synaptic transmission function at cold temperatures, as it is a vital component of ectothermic animals' survival. For determining how synaptic transmission is influenced by an acute change in temperature (20°C to 10°C within a minute) and chronic cold (10°C), the crayfish (Procambarus clarkii) neuromuscular junction (NMJ) was used as a model. To simulate chronic cold conditions, crayfish were acclimated to 15°C for 1 week and then to 10°C for 1 week. They were then used to examine the synaptic properties associated with the low output nerve terminals on the opener muscle in the walking legs and high output innervation on the abdominal deep extensor muscle. The excitatory postsynaptic potentials (EPSPs) of the opener NMJs increased in amplitude with acute warming (20°C) after being acclimated to cold; however, the deep extensor muscles showed varied changes in EPSP amplitude. Synaptic transmission at both NMJs was enhanced with exposure to the modulators serotonin or octopamine. The membrane resistance of the muscles decreased 33% and the resting membrane potential hyperpolarised upon warm exposure. Analysis of haemolymph indicated that octopamine increases during cold exposure. These results suggest bioamine modulation as a possible mechanism for ensuring that synaptic transmission remains functional at low temperatures.
Highlights
The effect of temperature on neuronal function has been of interest for years, as there are fundamental questions about how various ectothermic animals can adapt to extreme temperatures and, in some cases, live in conditions where other ectotherms cannot (Chung et al, 2012; Somero et al, 1996; Städele et al, 2015; Veselý et al, 2015)
Acute exposure to changes in temperature and modulators for low-output neuromuscular junction (NMJ) The low-output NMJs were assessed on the opener muscle of the first pair of walking legs (Fig. 1A)
The effect of rapid exposure (
Summary
The effect of temperature on neuronal function has been of interest for years, as there are fundamental questions about how various ectothermic animals can adapt to extreme temperatures and, in some cases, live in conditions where other ectotherms cannot (Chung et al, 2012; Somero et al, 1996; Städele et al, 2015; Veselý et al, 2015). Using model neural circuits and synaptic preparations, such as the stomatogastric nervous system and neuromuscular junctions of crustaceans, fundamental questions of the biological effects can be addressed (Städele et al, 2015). We used a robust crustacean species (crayfish, Procambarus clarkii) that can live in nearly freezing conditions for short periods (i.e. minutes) and in warm seasonal conditions (40°C) in nature. It is native to subtropical climates but can live across different temperature zones and is known as a robust invasive species throughout North America, Europe and Asia (Foster and Harper, 2007; Gherardi, 2010; Yue et al, 2010)
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