CC BY
25
Volga Neuroscience School 2016 Astroglial control of rhythm genesis in the brain
Effect of Previous Neuronal Activity on Characteristics of Action Potentials
E.N. Vasileva* and A.V. Semyanov
Institute of Neuroscience, Lobachevsky State University of Nizhny Novgorod, Nizhny Novgorod, Russia. * Presenting e-mail: vasileva@neuro.nnov.ru
Action potential has been being studied for many years, but it still perceived as signal, which operates according to the "all or none" rule, that does not fully reflect the importance of changes in the form of action potential. Therefore, the goal of this work was to study the impact of the previous activity of the neuron on the characteristics of the action potential.
The recordings of electrical activity of CA1 pyramidal neurons in the mice hippocampal slices were obtained in whole-cell current clamp mode. Cell firing in response to current steps of different amplitude, duration, and frequency was recorded. Then threshold, amplitude, half-width, the instantaneous frequency of AP and afterhy-perpolarization were analyzed. Threshold, amplitude, and half-width of the first AP don't depend on the current step, and in the next AP's threshold and half-width increases and amplitude decreases with the increasing of steps' amplitude. Previous neuronal activity also increases slow afterhyperpolarization and decreases the instantaneous frequency of AP's.
Because the form of action potential determines presynaptic Ca2+ entry activity-dependent changes of AP's characteristics can regulate synaptic transmission by changing the probability of neurotransmitter release.
Acknowledgements
This work was supported by the Russian Science Foundation (project 16-14- 00201).
Lactate and Ketone Bodies Regulate Astrocytic Calcium Dynamics in Early Postnatal Development
A. Lebedeva*, E. Shishkova, A. Semyanov
Institute of Neuroscience, Lobachevsky State University of Nizhny Novgorod, Nizhny Novgorod, Russia * Presenting e-mail: lebedeva@neuro.nnov.ru
Astrocytes may engage in the cellular mechanisms of learning and memory by regulation of energy metabolism. Lactate and pyruvate become energy sources for neurons during intensive work, in early ontogenesis and in some pathological conditions. However, the main energy substrates during early ontogenesis are ketone bodies [Zilbert-er et. al., 2010]. Since the neural activity depends on the availability of energy substrates supplied by astrocytes, this process can be considered as mechanism regulating neuronal function. Nevertheless, the role of ketone bodies, lactate and pyruvate in regulating astrocyte activity remains unclear. Using laser confocal microscopy, we have investigated how lactate, pyruvate and beta-hydroxybutyrate (thereafter, specific energy substrates), affect Ca2+ dynamics in astrocytes in rat hippocampal slices at different stages of postnatal brain development: postnatal day (P) 5, 15 and 30. The astrocytes were stained with Oregon Green BAPTA AM (7.95 |oM), Ca2+ sensor, and sulforhodamine 101 (200 nM), a specific astrocytic marker. The application of each of specific energy substrate significantly increased the frequency of astrocytic Ca2+ events at P5, but not at P15 or P30. However, the specific energy substrates application in the presence of bafilomycin A1 (4 |oM), a vesicular release blocker, decreased the frequency of Ca2+ events at P5. This suggests that specific energy substrates regulate astrocytic calcium activity at an early development stage though the changes in the vesicular release of neuro- and/or gliotransmitters. Since astrocytes play an important role in the brain development (e.g. the regulation of neuro- and gliogenesis, neuronal pathfinding, synaptogenesis), our results suggest that these processes can be affected by the availability of specific energy substrates.
Acknowledgements
This work was supported by the Russian Science Foundation under (project 15-14-30000).
OM&P
Opera Med Physiol 2016 Vol. 2 (S1) 111
