ABSTRACT
Ectothermic 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.
Footnotes
Competing interests
The authors declare no competing or financial interests.
Author contributions
Conceptualization: R.L.C., Y.Z., L.d.C.; Methodology: R.L.C., Y.Z.; Formal analysis: R.L.C., Y.Z., L.d.C.; Investigation: R.L.C., Y.Z., L.d.C.; Data curation: R.L.C., Y.Z.; Writing - original draft: R.L.C., Y.Z.; Writing - review & editing: R.L.C., Y.Z., L.d.C.; Supervision: R.L.C.; Project administration: R.L.C.
Funding
This research received no specific grant from any funding agency in the public, commercial or not-for-profit sectors.
Data availability
Cooper, R. (2018, October 10). Crayfish NMJ-Cold conditioning-Biology Open paper. Retrieved from osf.io/85qde.
- Received August 15, 2018.
- Accepted October 26, 2018.
- © 2018. Published by The Company of Biologists Ltd
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution and reproduction in any medium provided that the original work is properly attributed.