抄録
We have reported that there exist regional differences of propofol effects on GABA-mediated inhibitory synaptic transmission in vitro studies (Ishiguro M et al, JPS 56 suppl; s165, 2006). In this study, we aimed to investigate the relation between electrical stimulus intensity and inhibitory postsynaptic currents (IPSCs) without propofol in CA1 pyramidal cells (CA1-PCs) and dentate gyrus granule cells (DG-GCs) in rat hippocampal slices. The monosynaptic IPSCs were evoked by electrical stimulation of GABAergic interneurons and recorded from CA1-PCs and DG-GCs by a whole cell patch-clamp technique. The electrical stimuli (0.1ms pulses of 0.5-5mA) were delivered using bipolar stainless wire electrodes placed within 250 μ m of the recording pipette and near the somatic regions of the CA1-PCs and DG-GCs. IPSCs were evoked at various voltage command steps from -120 to +40mV (holding potential of -60 mV). By increasing the stimulus intensity, the amplitude of IPSCs in CA1-PCs and DG-GCs were enhanced in a double sigmoid manner with a notch at approximately 60% of the maximum stimulus intensity, as well as the decay time constant of IPSCs. There is no clear difference in the enhancement patterns of IPSC amplitude and decay time constant between CA1-PCs and DG-GCs.These results suggest that in CA1-PCs and DG-GCs, neural mechanisms for IPSCs evoked at the lower stimulus intensity (< c., 60%) might be different from those evoked at the higher intensity. [J Physiol Sci. 2007;57 Suppl:S148]
