| Summary: | Antarctic organisms have undergo a series of adaptations which allow them to live at water temperatures ~-2°C, and perform all physiological functions as similar taxa at warmer temperatures. In order to understand the adaptations underwent by the nervous system in the process of action potential generation, we studied the temperature dependence of extracellular field activity in two mollusk living in different thermal environments: the land snail Helix pomatia, and the antarctic limpet Nacella concinna. N. concinna specimens were collected in Fildes Bay (62°12'0'' 58°57'51''), Antarctica. Extracellular field potentials were recorded in the limpet cerebral ganglia from -2 to 15°C, having a maximum peak between 4 to 8 °C. Activity decreased at higher temperatures and in some experiments stops at 15°C. In H. pomatia ganglia the extracellular activity was almost inexistent below 10 °C and showed a peak between 15 to 22 °C, decreasing to almost zero over 32°C. These differences in neuronal activity can be explained by the differences in the set of voltage dependent ion channels, their temperature dependence of activation, or both. Because K+ channels are determinants in setting the firing patterns, we wanted to study how these channels are involved in the adaptation of neuronal activity and generation of firing pattens. In isolated ganglia the rhythmic activity is affected by the A-type K+ channel blocker 4-Aminopyridine, showing that this conductances is important for setting firing patterns and a possible candidate for the adaptation to low temperature.
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