A: Seizure occurrence after perfusion of the <i>in</i><i>vitro</i> isolated guinea pig brain with different K⁺ salt solutions.

<p>The white columns represent the total number of experiments. The light grey, dark grey and black columns mark the effects of the perfusion of K⁺ salts at 8, 14.2m 20 mM, respectively. <b>B</b>: Time at onset (black columns) and duration (white columns) of seizure activity after perfusion with 14.2 KPF₆, 14.2 mM KClO₄ and 20 mM KBF₄. <b>C</b>: Brain parenchyma concentration of two salts (KPF₆ and KBF₄) estimated by ¹⁹F MR spectroscopy on CA1-EC specimens, collected after arterial perfusion with 14.2 mM KPF₆ (n= 4; black column) and 20 mM KBF₄ (n= 3; grey column). </p

Effects of 4.2 mM KPF₆ (A), 14.2 mM KClO₄ (B) and 20 mM KCl (C) on the field potentials evoked in the piriform cortex by lateral olfactory tract (LOT) stimulation.

<p>Left, middle and right traces: before, during and after washout of the K⁺ salts, respectively.</p

KPF₆ 14.2 mM perfusion induced large amplitude depolarization events that propagated through the cortical mantel, from the hippocampus to the entorhinal (EC) and piriform cortex (PC).

<p>These events were interpreted as spreading depolarization phenomena (Somjen 2001). </p

A. Schematic protocol of the experiments. Electrophysiological recordings are performed for the entire experimental period

<p>Each perfusion of salts lasted 15 min. and was followed by 30 min. wash-out. Brain tissue samples were than collected and processed for the ¹⁹F MR spectroscopy. <b>B:</b> Structures of KX salts (X= PF₆^-, BF₄^-, ClO₄^-, Br^-, AcO^- and Cl^-) and electrostatic potential surfaces (B3LYP/6-311+G**) of individuals ions and ion pairs. Blue regions indicate positive potentials and red regions negative ones. Maximum values of the electrostatic potential, at K atom, and minimum values, at O, F, Br and Cl atoms are indicated besides each structure. Molecular volumes are also reported (ų).</p

Effects of perfusion of K⁺ salts in the <i>in</i><i>vitro</i> isolated guinea pig brain.

<p>A scheme of the position of the recording and stimulating (S1, on the lateral olfactory tract) electrodes is shown in the upper part of the figure. The upper set of traces illustrates the effect of 14.2 mM KPF₆ perfusion (right) compared to control (left); seizure activity was induced by this salt. In the lower part of the figure the effect of perfusion with 14.2 mM KClO₄ is shown. PC: piriform cortex; EC: entorhinal cortex; HIP: CA1 region of the hippocampus.</p