Fig. 8. Effects of pentobarbital on long-term potentiation (LTP) induction. ( A ) Pentobarbital, 30 μm ( solid bar ), did not completely inhibit the induction of N -methyl-d-aspartate receptor–dependent LTP ( filled circles ) induced by 100-Hz θ-burst stimulation (TBS; arrow ). Open circles show LTP in control slices. ( B ) Pentobarbital, 30 μm ( solid bar ), did not completely block the induction of N -methyl-d-aspartate receptor–independent LTP ( filled circle ) induced by 200-Hz TBS ( arrow ) in the presence of 1 μm MK-801 ( dotted bar ). Open circles show LTP in control slices. Traces to the right of the graphs show representative excitatory postsynaptic potentials (EPSPs) before ( dashed traces ) and 60 min after ( solid traces ) delivery of 100-Hz TBS ( upper ) in the presence of pentobarbital or 200-Hz TBS in the presence of MK-801 and pentobarbital ( lower traces ). ( C ) Pentobarbital did not alter N -methyl-d-aspartate–EPSPs. Scale bar : 2 mV, 5 ms .