Temperature-fastened sodium inactivation accounts for energy efficient cortical action potentials in mammalian brains
© Yu; licensee BioMed Central Ltd. 2012
Published: 16 July 2012
Recent experimental evidencs showed that action potential (AP) generation in mammalian, versus invertebrate, axons is remarkably energy efficient . Here we perform both computational (based on both traditional Hodgkin-Huxley model  and a cortical axon model  whose parameters are modified from experimental data) and experimental studies. Each supports that temperature is a major factor which directly modulates the level of energy cost of APs. Temperature increase results in a remarkable decrease in time constant of sodium channel closing and an increase in inactivation level of Na+ channel due to the Q10 effect (which quantifies the temperature dependent rate of biochemical reactions). This results in a marked reduction in overlap of the inward Na+, and outward K+ currents. As a consequence, the Na+ entry ratio gradually reaches to 1 (the theoretical optimal level, which requires only minimal Na+ charge for generating an AP) as temperature rises. Moreover, we also notice a remarkable exponential increase in firing rate and an exponential decrease in spike duration by both experimental and model studies. The total energy charge in response to a signal reaches a global minimum when temperature is around 37-42 oC. This suggests that warm body temperatures may help the mammalian brain to operate with minimal energy cost.
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