Post-tetanic depression of GABAergic synaptic transmission in rat hippocampal cell cultures

The effect of tetanic stimulation (30 Hz, 4 s) on evoked GABAergic inhibitory postsynaptic currents (IPSCs) was studied in cell cultures of dissociated hippocampal neurons with established synaptic connections. It was found that tetanic stimulation elicited post-tetanic depression (PTD) of the evoked IPSCs with a duration of more than 50 s in about 60% of the connections tested; post-tetanic potentiation was induced in 25% of the connections. We propose that the opposite effects of tetanization on IPSC amplitude are due to differences in the type of the interneuron that was tetanized. Since PTD in our experiments was usually accompanied by changes in the IPSC coefficient of variation and changes of a paired pulse depression, which are thought to reflect presynaptic mechanisms of modulation, we suggest that part of the PTD is due to a presynaptic mechanism(s).