Abstract
In contrast to the excitatory synaptic plasticity, the modulation of GABAA receptor-mediated inhibitory postsynaptic currents (IPSCs) that modify excitatory synaptic transmission has not been sufficiently characterized. Although post tetanic depression of electrically-evoked IPSCs has been described by several investigators, relatively few studies were made on potentiation of the IPSCs. In present experiments, changes in evoked and spontaneous GABAAergic synaptic transmission after tetanic stimulation were examined using acute slices of rat hippocampus. IPSCs were recorded from CA3 neurons, by patch-clamp recording method. Spontaneous IPSCs were recorded in the presence of specific inhibitors against excitatory glutamatergic currents. High frequency stimulation was applied with microelectrode. Transient facilitation of miniature and spontaneous IPSCs were detected after intensive tetanus. As to evoked IPSC, suppression, rather than facilitation, was observed after tetanization under similar conditions. By fluorescent imaging, changes of calcium concentration during IPSC recording were also followed in hippocampal slice preparation. Increment of intracellular calcium concentration was demonstrated upon high frequency stimulation. Contributions, to the IPSC modulation, of extra-cellular calcium as well as calcium elevation in post synaptic neuron were examined. In addition, effect of several calcium mobilizing reagents was studied, on the efficacy of inhibitory synapse. [Jpn J Physiol 55 Suppl:S142 (2005)]
