Neuronal ensembles and metabolic homeostasis during gamma oscillations in the hippocampal CA3 network

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The project B02 explores the energy foundations of complex brain information processing.

Gamma oscillations (30-100 Hz) occur in most regions of the cortex, including the hippocampus. They have been implicated in higher cognitive functions such as sensory perception, selective attention and memory formation. The patterned neuronal activity during gamma oscillations goes along with strongly increased energy expenditure. However, the relationship between activation of pyramidal cell ensembles during gamma oscillations and metabolic homeostasis is largely unknown.

Here, we will explore in detail (i) the spatio-temporal characteristics of pyramidal cell ensembles such as frequency and timing of action potentials, selective coupling, sparseness and distinctness and (ii) the mechanisms that ensure the underlying metabolic homeostasis in view of ion and water fluxes, energy expenditure and neurotransmitters. We will focus on persistent gamma oscillations in the local CA3 network of the hippocampus. We will combine electrophysiological techniques, oxygen recordings and live-cell fluorescence imaging at high spatio-temporal resolution, pharmacology, immunohistochemistry as well as sensitive biochemical and molecular biological methods in hippocampal slices. We aim to understand the foundations of functional pyramidal cell ensembles and the underlying neuroenergetics during complex information processing in a local cortical network.
Huchzermeyer C, Berndt N, Holzhütter HG, Kann O (2013) Oxygen consumption rates during three different neuronal activity states in the hippocampal CA3 network. J Cereb Blood Flow Metab 33:263-271.

Liotta A, Rösner J, Huchzermeyer C, Wojtowicz A, Kann O, Schmitz D, Heinemann U, Kovács R (2012) Energy demand of synaptic transmission at the hippocampal Schaffer-collateral synapse. J Cereb Blood Flow Metab 32:2076-83.

Kann O, Taubenberger N, Huchzermeyer C, Papageorgiou IE, Benninger F, Heinemann U, Kovács R (2012) Muscarinic receptor activation determines the effects of store-operated Ca(2+)-entry on excitability and energy metabolism in pyramidal neurons. Cell Calcium 51:40-50.

Kann O, Huchzermeyer C, Kovács R, Wirtz S, Schuelke M (2011) Gamma oscillations in the
hippocampus require high complex I gene expression and strong functional performance of mitochondria. Brain 134:345-358.

Huchzermeyer C, Albus K, Gabriel HJ, Otáhal J, Taubenberger N, Heinemann U, Kovács R, Kann O (2008) Gamma oscillations and spontaneous network activity in the hippocampus are highly sensitive to decreases in pO2 and concomitant changes in mitochondrial redox state. J Neurosci 28:1153-1162.

Kann O, Kovács R, Njunting M, Behrens CJ, Otáhal J, Lehmann TN, Gabriel S, Heinemann U 2005) Metabolic dysfunction during neuronal activation in the ex vivo hippocampus from chronic epileptic rats and humans. Brain 128:2396-2407.

Spatiotemporal Patterning
Kann O, Schuchmann S, Buchheim K, Heinemann U (2003) Coupling of neuronal activity and mitochondrial metabolism as revealed by NAD(P)H fluorescence signals in organotypic hippocampal slice cultures of the rat. Neuroscience 119:87-100.

*Principal investigators of other projects within the CRC