Assessment of anoxia tolerance and photoperiod dependence of GABAergic polarity in the pond snail Lymnaea stagnalis

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• 作者：Leslie T. Buck^a ; ^c ; ^{les.buck@utoronto.ca} ; Hilary C. Bond^a ; Aqsa Malik^b
• 关键词：APf ; action potential frequency ; ANOVA ; Analysis of Variance ; CCC ; cation-chloride co-transporter ; [Cl&minus ; ] ; Chloride Concentration ; GABA ; gamma-aminobutyric acid ; [GABA] ; GABA concentration ; KCC2 ; K+-Cl&minus ; cotransporter isoform 2 ; LD ; light ; dark ; MΩ ; megaohm ; Vm ; membrane potential ; μmol ; micromolar ; mmol ; millimolar ; NKCC1 ; Na+-K+-2Cl&minus ; cotransporter isoform 1 ; PeDG ; pedal dorsal ganglia ; EGABA ; reversal potential for GABA
• 刊名：Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
• 出版年：2017
• 出版时间：January 2017
• 年：2017
• 卷：203
• 期：Complete
• 页码：193-200
• 全文大小：633 K
• 卷排序：203

文摘

The pond snail Lymnaea stagnalis is reported to be anoxia-tolerant and if the tolerance mechanism is similar to that of the anoxia-tolerant painted turtle, GABA should play an important role. A potentially confounding factor investigating the role of GABA in anoxia tolerance are reports that GABA has both inhibitory and excitatory effects within L. stagnalis central ganglion. We therefore set out to determine if seasonality or photoperiod has an impact on: 1) the anoxia-tolerance of the intact pond snail, and 2) the response of isolated neuroganglia cluster F neurons to exogenous GABA application. L. stagnalis maintained on a natural summer light cycle were unable to survive any period of anoxic exposure, while those maintained on a natural winter light cycle survived a maximum of 4 h. Using intracellular sharp electrode recordings from pedal ganglia cluster F neurons we show that there is a photoperiod dependent shift in the response to GABA. Snails exposed to a 16 h:8 h light:dark cycle in an environmental chamber (induced summer phenotype) exhibited hyperpolarizing inhibitory responses and those exposed to a 8 h:16 h light:dark cycle (induced winter phenotype) exhibited depolarizing excitatory responses to GABA application. Using gramicidin-perforated patch recordings we also found a photoperiod dependent shift in the reversal potential for GABA. We conclude that the opposing responses of L. stagnalis central neurons to GABA results from a shift in intracellular chloride concentration that is photoperiod dependent and is likely mediated through the relative efficacy of cation chloride co-transporters. Although the physiological ramifications of the photoperiod dependent shift are unknown this work potentially has important implications for the impact of artificial light pollution on animal health.