Figure 1.

Effects of tissue oxygenation on gamma oscillations and associated mitochondrial redox responses in CA3. A, Local field potentials were recorded in stratum pyramidale, and ACh (10 μm) was continuously applied in the presence of cholinesterase inhibitor physostigmine (2 μm) to evoke robust and persistent gamma oscillations. B, From recordings and conditions as illustrated in A, power spectra were calculated from data segments of 60 s. In the histogram, the gamma band power (30–80 Hz) is significantly reduced at 20% O₂ (p < 0.001; n = 15). C, Simultaneous recordings of NAD(P)H fluorescence in stratum radiatum (orange) and pyramidale (light blue) as well as [K⁺]_o (black) and local field potentials (data not shown) in stratum pyramidale were made during application of ACh (10 μm; bottom gray bar). Initially, the increase in [K⁺]_o was associated with a biphasic NAD(P)H fluorescence transient (dip and overshoot component), which transformed into a persistent NAD(P)H elevation (black arrow) when gamma oscillations were fully established (illustrated as top gray bar). Note that persistent NAD(P)H elevations were significantly larger in stratum radiatum. Figure 5A illustrates the selection of regions of interest for fluorescence imaging. *p < 0.05.