Fig. 4. Effects of 30 μm propofol on long-term potentiation induction and maintenance. (  A ) One hundred–hertz θ-burst stimulation (TBS;  arrow ) induced long-term potentiation in control slices (  open circles ). (  B ) Administration of 30 μm propofol for 20 min before and during TBS (  solid bar ) blocked long-term potentiation induction (  solid circles ). (  C ) TBS induced long-term potentiation in slices treated with 30 μm propofol (  filled circles ) when propofol administration was begun 5 min after delivery of TBS (  solid bar ).  Traces to the right of each graph show representative excitatory postsynaptic potentials (EPSPs) obtained before (  dashed traces ) and 60 min after TBS (  solid traces ). EPSPs were obtained from a control slice (  upper traces ), a slice treated with propofol before and during the delivery of TBS (  middle set of traces ), and a slice treated with propofol after TBS (  bottom traces ).  Scale bar : 2 mV, 5 ms .