MUSCIMOL-INDUCED DEATH OF GABAERGIC NEURONS IN RAT-BRAIN AGGREGATING CELL-CULTURES

During brain development, spontaneous neuronal activity has been shown to play a crucial role in the maturation of neuronal circuitries. Act ivity-related signals may cause selective neuronal cell death and/or r earrangement of neuronal connectivity. To study the effects of sustain ed inhibitory activity on developing inhibitory (GABAergic) neurons, t hree-dimensional primary cell cultures of fetal rat telencephalon were used. In relatively immature cultures, muscimol (10 mu M), a GABA(A) receptor agonist, induced a transient increase in apoptotic cell death , as evidenced by a cycloheximide-sensitive increase of free nucleosom es and an increased frequency of DNA double strand breaks (TUNEL label ing). Furthermore, muscimol caused an irreversible reduction of glutam ic acid decarboxylase activity, indicating a loss of GABAergic neurons . The muscimol-induced death of GABAergic neurons was attenuated by th e GABA(A) receptor blockers bicuculline (100 mu M) and picrotoxin (100 mu M), by depolarizing potassium concentrations (30 mM KCI) and by th e L-type calcium channel activator BAY K8644(2 mu M). As compared to t he cholinergic marker (choline acetyltransferase activity), glutamic a cid decarboxylase activity was significantly more affected by various agents known to inhibit neuronal activity, including tetrodotoxin (1 m u M), flunarizine (5 mu M), MK 801 (50 mu M) and propofol (40 mu M). T he present results suggest that the survival of a subpopulation of imm ature GABAergic neurons is dependent on sustained neuronal activity an d that these neurons may undergo apoptotic cell death in response to G ABA(A) autoreceptor activation. (C) 1998 Elsevier Science B.V.