DOSE-DEPENDENT EFFECTS OF TETRAETHYLAMMONIUM ON CIRCLING SPREADING DEPRESSIONS IN CHICKEN RETINA

The K+-channel blocker tetraethylammonium (TEA) was applied to study i ts effects in self-sustaining, circling spreading depression in the ch icken retina (RSD), Extracellular K+ (K-e(+)) activities and the direc t-current (DC) signal were recorded using double-barrelled microelectr odes. Superfusion of TEA-concentrations of 10 to 250 mu M for 4 to 7 m in reduced the RSD-associated DC amplitude (by 9 to 45%) and the maxim um of the K-e(+) concentration (by 9 to 34%) in a dose-dependent manne r, Propagation velocity of the RSD was lowered by 24%, At concentratio ns higher than 250 mu M TEA (0.5 to 10 mM), the propagation was slowed by more than 60%, after which the RSD disappeared, Recovery upon repe rfusion with Ringer was immediate, These observations illustrate: 1) T EA affects the K-e(+) changes during RSD at very low concentrations. 2 ) The reduced K-e(+) transients are accompanied by a reduction of the DC shifts, 3) These changes of the electrical properties of the RSDs a re paralleled by a reduction of the propagation velocity, 4) The effec ts of TEA are reversible, 5) The changes of these parameters occur dos e-dependently, These data suggest a close relationship between the amp litudes of the ionic/electric changes during RSDs and the mechanisms o f propagation. (C) 1998 Wiley-Liss, Inc.