Impaired mitochondrial function abolishes gamma oscillations in the hippocampus through an effect on fast-spiking interneurons
Sir, Synchronous neuronal oscillations in the gamma frequency band (30–80 Hz) are implicated in a wide range of cognitive processes, including memory formation (Varela et al ., 2001) and sensory processing (Singer, 1993; Gray, 1994). This rapid, temporally co-ordinated activity in spatially distributed areas of cortex is highly energy dependent, producing large changes in blood-oxygen level dependent signals in vivo and showing exquisite sensitivity to hypoxia in vitro (Huchzermeyer, 2008). Gamma oscillations are generated by reciprocal excitation and inhibition in networks of electrically coupled pyramidal cells and GABAergic interneurons (Fisahn et al ., 1998; Cunningham et al ., 2003; Hajos et al ., 2004). Synchronous firing of networks of basket-cell interneurons at gamma frequency produces phasic inhibition of pyramidal cells, the periods when this inhibition is minimal, providing temporal windows for pyramidal cell firing. Pyramidal cell firing in turn provides reciprocal tonic excitation onto interneurons, allowing the cycle to continue (Traub et al ., 1996). The research article by Kann et al . (2011) demonstrates the critical dependence of gamma oscillations upon mitochondrial function. However, little is known about the relative energetic requirements of the different cellular components of this network. We have addressed this issue with intracellular recordings of pyramidal cells and interneurons undergoing gamma oscillations under conditions of metabolic stress in vitro . Rat hippocampal slices (450 μm horizontal sections) were maintained in a recording chamber at the interface between 95% …