Fig. 6. Sevoflurane does not affect posttetanic potentiation (PTP) at the visceral dorsal 4 (VD4)–left pedal dorsal 1 (LPeD1) synapse. To test whether sevoflurane blocks VD4-induced PTP in LPeD1, synapses were tested electrophysiologically. ( A ) Action potentials in VD4 (at arrow ) generated 1:1 excitatory postsynaptic potentials (EPSPs) in LPeD1 under control ( i ) and various anesthetic conditions ( ii ) and after washout ( iii ). Although VD4-induced EPSPs were significantly suppressed by all sevoflurane concentrations used ( A ), the ratio between the pretetanus and posttetanus EPSPs did not change significantly ( B ), even for 3% sevoflurane, which blocked the synaptic transmission almost completely.