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Volga Neuroscience School 2016 Astroglial control of rhythm genesis in the brain References
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Up- and Down- Regulation of H-Channels Conductance in CA1 Hippocampal Neurons
M.S. Doronin*, Yu.V. Dembitskaya, A.V. Semyanov
Institute of Neuroscience, Lobachevsky State University of Nizhny Novgorod, Nizhny Novgorod, Russia. * Presenting e-mail: [email protected]
N-methyl-D-aspartate receptors (NMDARs) play an important role in induction of long-term potentiation (LTP). During LTP induction activation of synaptic NMDARs also triggers up-regulation of hyper-polarization-activated (h) channels (Fan et al., 2005). In contrast, prolonged activation of extrasynaptic NMDARs down-regulates h-channels (Gh) (Wu et al., 2012). Thus, Gh plasticity depends on synaptic and extrasynaptic NMDARs activation and balances the overall neuronal excitability increased by LTP. However, it remains unknown if this plasticity can be specific to subcellular regions and if local plasticity can affect the average conductance of the whole neuron.
Therefore, we investigated if the Gh up-regulation in one dendritic branch and down-regulation in another branch might occur simultaneously during induction of LTP and control the overall cell conduct-
We used the two-photon imaging and single-photon glutamate uncaging in order to monitor the state of different subcellular compartments. We performed whole-cell patch-clamp recordings in CA1 pyramidal neurons of C57BL/6 mice (male, P28-35) hippocampal slices. Slices were pre-incubated with a specific inhibitor of vacuolar-type H+-ATPase - bafilomycin A1 (4 |M) to prevent the vesicular release. Neurons were loaded with 50 |M Alexa 594 through the patch pipette that enabled us to visualize dendritic shafts and spines by using the two-photon excitation with the 830 nm wavelength. 400 |M MNI-caged-L-glu-tamate was applied to the bath and uncaged with 405 nm laser at the vicinity of several (6-9) dendritic spines for 5-10 ms. Uncaging-induced EPSPs (uEPSPs) were recorded in soma. The spike-time dependent plasticity-inducing (STDP) protocol was applied in order to induce local LTP in specific dendritic spines. In these spines ("active") local glutamate uncaging was combined with somatic current injections triggering theta-bursts of action potentials. The amplitude and half-width of uEPSPs in "active" spines, their neighbors on the same dendritic brunch ("neighbor" spines) and spines at different dendritic brunch ("remote" spines) were compared before and after induction of STDP.
We found a significant decrease in the input resistance of the neurons (n=8, p=0.0234), suggesting that plasticity induction in localized dendritic shafts might affect overall cell conductance. However, we did not observe a significant difference in the amplitude and half-width of uEPSP in "active", "neighbor" or "remote" spines. These results might indicate an important mechanism of homeostasis that controls synaptic strength and cell excitability, acts via h-channels and equilibrate overall cell conductance.
Acknowledgements
This study was supported by the RFBR foundation (research grant 16-34-00961 MO^_a).
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Opera Med Physiol 2016 Vol. 2 (S1) 101
