INVOLVEMENT OF GABA-A RECEPTORS IN THE OUTGROWTH OF CULTURED HIPPOCAMPAL-NEURONS

Whereas GABA is a major inhibitory neurotransmitter in the adult central nervous system, recent experiments performed in our laboratory have shown that the activation of GABA(A) receptors in the hippocampus leads to excitatory effects during the early post-natal period. The possible consequence of a depolarizing effect of GABA was assessed on the neuritic outgrowth of embryonic hippocampal neurons in culture. No morphological alterations were observed when hippocampal neurons were cultured for three days in the presence of muscimol, a GABA(A) receptor agonist. In contrast, the neuritic outgrowth of cultured hippocampal neurons was profoundly affected by the presence of bicuculline in the culture medium. In the presence of this GABA(A) receptor antagonist neurons displayed a reduction in the number of primary neurites and branching points, resulting in a concomitant decrease of the total neuritic length. Thus, this study suggests that GABA acting on GABA(A) subtype of receptors, is able to affect the development of the hippocampus.