[The effect of exogenous concentration of chlorine and calcium ions on GABA and bicuculline action on the K+ -induced release of H3-noradrenaline from synaptosomes].

Effects of GABA (10(-3) M) and its antagonist bicuculline on K+-evoked release of H3-NA were studied in synaptosomes of rat mesodiencephalic region in the absence of Cl-, Ca2+ ions and in the presence of Ca2+ antagonist Mn2+ ions. K+-evoked release of H3--NA activated by GABA did not change in a Cl--free medium. Bicuculline blocked the activating effect of GABA. Some noticeable activation of K+-evoked release of H3--NA was observed in Cl- and Ca++--free medium. GABA, however, inhibited this process. Under these conditions, K+-evoked release of H3--NA did not occur in the presence of bicuculline. Mn2+ ions blocked GABA- and bicuculline--activated K+--evoked release of H3--NA. Taking into account the opposite effect of GABA on K+-evoked release of H3--NA depending on ionic changes in incubation media, the possibility of Cl- and Ca2+ ions participation in the GABA effect is considered.