Intracellular pH effects of lactate isomers on cortical neurons.

<p>Intracellular pH measured using BCECF and calibrated <i>in situ</i> in cortical neurons. (a) Original pH trace during sequences of L- and D-lactate application. (b) Summary of acidification (pH amplitude) measured during L- and D-lactate application. (n = 39 cells; 7exp).</p

D-lactate effects on neuronal activity.

<p>(a) Sample trace of calcium transients in control or 5 mM D-lactate containing solution. (b) D-lactate substantially decreased calcium transient frequency. (c) The concentration-response analysis yielded an apparent IC₅₀ of 4.6±1.2 mM (n = 127 cells; 21exp).</p

Effects of L-lactate on calcium spiking frequency.

<p>(a) Original traces of calcium transients in control or 5 mM L-lactate containing solution. (b) Calcium spiking frequency for principal glutamatergic neurons and GABAergic interneurons are shown as percent of activity measured during control solution. Data are obtained from 49 principal cells and 35 interneurons from 13 experiments.</p

Neuronal activity monitored with calcium imaging.

<p>Comparison between simultaneous intracellular calcium imaging sampled at a frame rate of 10 Hz and whole-cell patch clamp recordings. A representative experiment out of 15 is shown with the upper trace representing calcium transients (arbitrary fluorescence units, AFU) and lower trace action potentials recorded in current-clamp configuration from the same neuron. The tick marks above the calcium trace indicate the occurrence of action potentials detected in the same cell using patch-clamp recordings.</p

Energy metabolite dependency of calcium spiking frequency.

<p>Calcium spikes frequency shown as percent of activity measured during control solution. (a) Effects of pyruvate on calcium spiking frequency (n = 188 cells, 24 exp). Glucose (5 mM) was present throughout the experiments. (b) Effects of glucose concentration on spiking frequency (n = 68 cells, 10 exp).</p

Concentration dependency of L-lactate effects.

<p>The decrease in calcium spiking frequency was concentration dependent. Apparent IC₅₀ values obtained by nonlinear curve fitting yielded 4.2±1.9 mM for principal neurons (n = 175 cells, 56 exp) and 4.2±2.8 mM for GABAergic neurons (n = 83 cells, 35 exp).</p

HCA1 receptor involvement in the lactate sensitivity.

<p>(a) Confocal images showing immunostaining for NeuN (green), HCA1 (red) and the merged image in mouse primary cortical neurons. Scale bar, 20 µm. (b) Representative Western blot showing that HCA1 is expressed in mouse primary cortical neuronal cultures. Each track represents one independent cultured dish of mouse primary cortical neurons (c) Comparison of lactate effect on calcium spiking frequency in cells incubated or not with pertussis toxin (PTX). PTX incubation strongly reduced the effects of lactate on neuronal activity. Data are obtained from 8 experiments and 61 cells for non-treated group and 8 experiments and 62 cells for PTX treated group.</p