An experimental study of the effect of isoflurane on epileptiform bursts.
The effect of isoflurane on penicillin- and picrotoxin-induced epileptiform activity was tested using hippocampal slice preparations. Isoflurane reduced both the frequency of spontaneous epileptiform bursts and the number of population spikes within each burst in a dose-dependent manner. The last population spikes in the burst were most sensitive to the anesthetic, whereas the first 4-6 spikes were quite resistant and persisted until spontaneous activity was abolished at 3% isoflurane. Isoflurane increased the stimulus current required to evoke epileptiform bursts and shifted the relationship between stimulus current and population spike amplitude to the right. At 3% isoflurane, a dose that usually causes iso-electric EEG and abolishes all spontaneous epileptiform activity, responses could still be evoked, and then invariably had an epileptiform pattern. The maximum response was reduced compared to control and 1.5% isoflurane. With isoflurane there was a reduced tendency for activity to be transmitted from one region within the hippocampus to the other. This effect was also dose-dependent. However, transmitted activity always retained a typical epileptiform character, although the number of population spikes within a train to some extent decreased with increasing concentrations of isoflurane.
Langmoen
I A
IA
Institute for Surgical Research, Rikshospitalet, University of Oslo, Norway.
Hegstad
E
E
Berg-Johnsen
J
J
D000818:Animals; D004569:Electroencephalography / Q000187:drug effects; D004827:Epilepsy / Q000503:physiopathology*; D006624:Hippocampus / Q000187:drug effects; D066298:In Vitro Techniques; D007530:Isoflurane / Q000494:pharmacology*; D009475:Neurons, Afferent / Q000187:drug effects; D010852:Picrotoxin / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar
D007530:Isoflurane; D010852:Picrotoxin