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 .