INTRACELLULAR CONTROL OF GABB(A) RECEPTOR RESPONSES IN HIPPOCAMPAL-NEURONS - ROLE OF PHOSPHORYLATION

Recent studies show that GABA(A)-receptors mediated responses in the h ippocampal cells are suppressed upon increases in intracellular Ca2+ [ Ca2+](i). A series of experiments were carried out to evaluate the phy siological significance of this modulatory action of [Ca2+](i). We sho w that GABA(A)-responses are suppressed by a preceding NMDA applicatio n in hippocampal cells. Furthermore the suppressive effect is mediated via an increase in [Ca2+](i). Additional data reveal that NMDA applic ation suppressed the GABA(A) response by initiating an Ca2+ dependent dephosphorylation process and the suppression is prevented by intracel lular ATP-gamma-S or okadaic acid. Our study suggest that there intera ctions between the excitatory synaptic responses and the inhibitory sy naptic responses may be effected with intracellular Ca2+ serving as a second messenger.