Fig. 1.
From: Relationship between oxygen consumption and neuronal activity in a defined neural circuit
Measurements of O2 levels in isolated preparations. a, b Photomicrograph, depicting an isolated head of a stage 53 tadpole (a1), a schematic transverse section of the hindbrain (a2), and a cross-sectioned head (b) at a rostro-caudal level indicated by the trapezoid in a1; red and blue circles and arrows in a2 indicate movements of the O2 electrode within the grid (white dots in b), used to construct the O2 profile (b). c Dual recordings of O2 concentrations in the bath and above the floor of the IVth ventricle in steps of 0.2 mm. d O2-concentration profile (mean ± SEM) of a midline depth track above the IVth ventricle (a2) in control (intact; color-coded) and metabolically inactive (EtOH-fixated; gray) preparations. e, f Recording of the ventricular O2 concentration in an EtOH-fixated preparation (e) during temporary increase of the bath O2 level to 650 μmol/l (gray area), and of an intact preparation (f) after bath-application of KCN (light pink area; 500 μmol/l); note that KCN causes an adjustment of the ventricular O2 level to the bath O2 level (single arrow in f) that remains matched (double arrow in f) when the bath O2 level is further increased (dark pink area). g Boxplot, depicting O2 concentrations in air-saturated bath solution (black), at the ventricular floor (red), and within the hindbrain (blue) in controls, in EtOH-fixated and KCN-treated preparations; note that EtOH-fixation and bath-application of KCN cause a significant increase of ventricular O2 concentrations to bath Ringer levels (***p < 0.0001; Mann-Whitney U test). h Scatter plot depicting coinciding ventricular and bath O2 levels in metabolically inactive (black dots, EtOH-fixated) or oxidative phosphorylation-impaired (pink dots, KCN) preparations. O2 levels in b–f are color-coded from blue (0 μmol/l) to red (300 μmol/l) to yellow (600 μmol/l); transverse hindbrain schemes indicate motion (c) or position (e, f) of the O2 electrode. OT, optic tectum; R, rostral; C, caudal; SC, spinal cord; N, number of preparations