Objective To investigate the combined effects of corticosterone and propofol on long-term depression (LTD) in
hippocampal
CA1 neurons, which affects learning and memory together with long-term potentiation (LTP) .Methods Male Wistar rats weighing 40-60 g were killed by cervical dislocation. Brains were immediately removed. Hippocampus was isolated and cut at 400 fun thickness. Thirty
hippocampal slices were randomly divided into S groups ( n = 6 ) : Ⅰ control group; Ⅱ intralipid group; Ⅲ propofol group; Ⅳ corticosterone group and Ⅴ propofol + corticosterone group. In control group the hippocampal slices were incubated in artificial CSF for 60 min. In group Ⅱ - Ⅴ the hippocampal slices were incubated with 100 μmol · L-1 intraiipid ( Ⅱ ), 100μmol·L-1 propofol (Ⅲ), 10μmol·L-1 corticosterone (Ⅳ) or 100μmol·L-1 propofol + 10μmol·L-1 corticosterone ( Ⅴ ) for 60 min. The
baseline excitatory postsynaptic currents (EPSCs) were recorded using whole-cell patch clamp technique. The holding potential was - 50 mV. The Schaffer collateral/commissural pathway was then stimulated with low frequency stimulation (LFS, 900 pulses at 3 Hz) . EPSCs were again recorded and the LTD was determined.Results In control and intraiipid group LTD was inducted after LFS and the EPSCs were 58.2% and 57.9% of the baseline 10-40 min after LFS, and there was no significant difference between the groups (P>0.05). The EPSCs 10-40 min after LFS were 40.8% of the baseline (propofol group), 45.4% of the baseline (corticosterone group) and 25.4% of the baseline (propofol + corticosterone group) respectively, significantly lower than that in group Ⅰ and Ⅱ ( P < 0.05) . The EPSC value 10-40 min after LPS in group Ⅴ was significantly lower than that in the other four groups.Conclusion 100 μmol · L-1 propofol or 10 μmol · L-1 corticosterone alone enhances the LFS-induced LTD in hippocampal CA1 pyramidal neurons of rats. Propofol and corticosterone potentiate each other in the development of LTD in the hippocampal CA1 neurons.