The dorsal cortex of<i>Trachemys scripta</i>as a physiological assay for the study of the molecular mechanisms of anoxia tolerance

Freshwater turtles spend the winters at the bottom of ice-covered lakes, surviving without oxygen during the winter months. This ability is unique to turtles and makes them ideal for studying the molecular mechanism of anoxia tolerance. Previous studies have shown that adenosine protects the brain by reducing brain activity and therefore diminishes the brain’s use of energy to match the limited supply of energy in anoxic conditions. The molecular mechanism within cells that leads to the survival of neurons after adenosine activation is largely unknown. Possible candidates including members of the mitogen-activated protein kinase (MAPK) family, such as the extracellular signal-regulated kinase one and two (ERK1/2). This study introduces the dorsal cortex of Trachemys scripta as a physiological assay for the study of the molecular mechanism of anoxia tolerance. We hypothesized that the amplitude of thalamocortical field potentials would decrease during anoxia but remain relatively constant during normal oxygen conditions. The in vitro cortical preparation of T. scripta was used to record cortical field potentials in response to stimulation of the lateral forebrain bundle. The brain, rostral to the cerebellum, was removed from twelve turtles and cut down the midsagittal plane to separate the right and left hemispheres. One hemisphere was placed in a recording chamber and perfused with Ringer’s bubbled with either 95% O 2 / 5% CO 2 or 95% N 2 /5% CO 2 . Twenty-one biphasic pulses with a 1 second interpulse interval were delivered every 10 minutes for an hour. The 21 field potentials were averaged at every time point to obtain an average field potential. The maximal slope of the average field potential was compared between the oxygen and nitrogen conditions. The maximal slope tended to decrease under the nitrogen condition, with an average slope at 60 minutes of 48.1 ± 15% of the slope at time 0 (n=6), which was lower than the maximal slope under the oxygen condition (97.5 ± 57.7%, n=8). A two-way ANOVA indicated that the interaction between gas and time was significant (p &lt; 0.001). This study demonstrates that the turtle in vitro cortical preparation can be used to study the molecular mechanisms of anoxia tolerance. Drugs can be easily perfused on the preparation through the Ringer’s solution, facilitating the identification of the kinases involved in the reduction of neural activity that accompanies anoxia in T. scripta. Hamilton College This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.