Sevoflurane Blocks the Induction of Long-term Potentiation When Present during, but Not When Present Only before, the High-frequency Stimulation.

BACKGROUND: This study tests the hypothesis that sevoflurane blocks long-term potentiation only if it is present during the high-frequency stimulation that induces long-term potentiation.

METHODS: Long-term potentiation, an electrophysiologic correlate of memory, was induced by high-frequency stimulation and measured as a persistent increase in the field excitatory postsynaptic potential slope in the CA1 region.

RESULTS: Long-term potentiation was induced in the no sevoflurane group (171 ± 58% vs. 96 ± 11%; n = 13, mean ± SD); when sevoflurane (4%) was present during the high-frequency stimulation, long-term potentiation was blocked (92 ± 22% vs. 99 ± 7%, n = 6). While sevoflurane reduced the size of the field excitatory postsynaptic potential to single test stimuli by 59 ± 17%, it did not significantly reduce the size of the field excitatory postsynaptic potentials during the 100 Hz high-frequency stimulation. If sevoflurane was removed from the artificial cerebrospinal fluid superfusing the slices 10 min before the high-frequency stimulation, then long-term potentiation was induced (185 ± 48%, n = 7); this was not different from long-term potentiation in the no sevoflurane slices (171 ± 58). Sevoflurane before, but not during, ⊖-burst stimulation, a physiologic stimulus, did not block the induction of long-term potentiation (151 ± 37% vs. 161 ± 34%, n = 7).

CONCLUSIONS: Sevoflurane blocks long-term potentiation formation if present during the high-frequency stimulation; this blockage of long-term potentiation does not persist if sevoflurane is discontinued before the high-frequency stimulation. These results may explain why short periods of insufficient sevoflurane anesthesia may lead to recall of painful or traumatic events during surgery.