Abstract
Comparing with the excitatory synaptic plasticity, the modulation of GABAA receptor-mediated inhibitory postsynaptic currents (IPSCs) that modify excitatory synaptic transmission has not been well characterized. Post tetanic depression of electrically-evoked IPSCs has been reported by several investigators. However, relatively few investigations were made on potentiation of the IPSCs. We examined changes of evoked and spontaneous GABAAergic synaptic transmission after tetanic stimulation, in acute slices of rat hippocampus. Using patch-clamp recording method, IPSCs were recorded from CA3 neurons. Excitatory glutamatergic currents were blocked by specific inhibitors during recording of spontaneous IPSCs. High frequency stimulation was applied by microelectrode. After intensive tetanus, transient and marked facilitation of spontaneous IPSCs were observed. Miniature IPSCs, recorded in the presence of tetrodotoxin, were also facilitated by the tetanic stimulation. Suppression, rather than facilitation, of evoked IPSC was observed after tetanization under similar conditions. The facilitation of the spontaneous IPSC was still detected in nominally Ca2+-free solution, though the control IPSC at rest was depressed by Ca2+ elimination. In addition, increment of intracellular calcium concentration after high frequency stimulation was also demonstrated in hippocampal slice preparation by fluorescent imaging. [Jpn J Physiol 54 Suppl:S152 (2004)]
