Figure 3.

Depth profiles of partial oxygen pressure (pO₂) during the three different activity states. The activity states of the hippocampal CA3 network (Figure 2) were verified in each individual slice culture and pO₂ depth profiles were recorded with vertical steps of 16 μm. (A) Representative sample traces of pO₂ depth profiles in the absence of spiking (TTX, black trace), spontaneous network activity (SPON, dark gray trace), and cholinergically induced gamma oscillations (GAM, light gray trace). Tetrodotoxin (TTX, 1 μmol/L) as well as acetylcholine (2 μmol/L) and physostigmine (400 nmol/L) for induction of gamma oscillations were applied with the recording solution. (B) Quantification of lowest pO₂ values as determined during the three different activity states, i.e., TTX (n=8), SPON (n=19), and GAM (n=8). Lowest pO₂ values are indicated by black dots in the example traces (A). (C) Quantification of pO₂ values at five defined depths in slice cultures, i.e., at the upper slice surface (surface; depth level 1), in the middle of upper surface and slice core (depth level 2), in the slice core (core; depth level 3), in the middle of slice core and lower slice surface (depth level 4), and at the lower slice surface (bottom, depth level 5) for TTX (n=8), SPON (n=19), and GAM (n=8). Statistical significance is marked by asterisks (P<0.05).