title: The effect of isoflurane and sevoflurane on cerebrocortical presynaptic Ca2+ and protein kinase C activity.
abstract: Protein kinase C (PKC) is an important enzyme involved in the regulation of neurotransmission and might also be important in the mediation of ischemic neuronal death. PKC has been implicated as a target of volatile anesthetics as well as in anesthetic protection against ischemia. The present study tested the effect of isoflurane and sevoflurane, both used in neuroanesthetic practice, on presynaptic free cytosolic Ca2+ ([Ca2+](i)) and PKC activity. To measure [Ca2+](i) and PKC activation simultaneously, rat synaptosomes, mostly containing presynaptic terminals, were loaded with the fluorescent probes fura-2 and fim-1, respectively. The synaptosomes were exposed to either isoflurane or sevoflurane in concentrations corresponding to 1 and 2 MAC values in rats, both in Ca2+-containing and Ca2+-free medium. After 8 minutes of anesthetic exposure, 1 mM 4-aminopyridine was added to induce membrane depolarization. Isoflurane 1 and 2 MAC increased the basal PKC activity after 8 minutes in Ca2+-containing medium by 15.1% (3.6%) and 30.5% (5.5%) compared with control, respectively [mean (SEM); n = 9, both values P < 0.05]. Sevoflurane 2 MAC transiently decreased but thereafter increased the PKC activity (P < 0.05). In Ca2+ -free medium sevoflurane attenuated the PKC activity (P < 0.05). The anesthetics did not alter the depolarization-evoked enzyme activation. Furthermore, 2 MAC of both isoflurane and sevoflurane increased the basal- and attenuated the depolarization-evoked increase in [Ca2+](i) (P < 0.05). The present study supports the hypotheses that volatile anesthetics affect presynaptic PKC activity and that the anesthetic effect on enzyme activation seems to be related to an increase in [Ca2+](i).
authors.affiliation: Institute for Surgical Research and Department of Neurosurgery, Rikshospitalet University Hospital, Oslo, Norway. cmoe@klinmed.uio.no
authors.forename: Morten C
authors.initials: MC
authors.lastname: Moe
authors.forename: Jon
authors.initials: J
authors.lastname: Berg-Johnsen
authors.forename: Geir A
authors.initials: GA
authors.lastname: Larsen
authors.forename: Elin B
authors.initials: EB
authors.lastname: Kampenhaug
authors.forename: Morten L
authors.initials: ML
authors.lastname: Vinje
mesh_terms: D018685:Anesthetics, Inhalation / Q000494:pharmacology*; D000818:Animals; D002540:Cerebral Cortex / Q000201:enzymology*; D005260:Female; D007530:Isoflurane / Q000494:pharmacology*; D008738:Methyl Ethers / Q000494:pharmacology*; D017729:Presynaptic Terminals / Q000201:enzymology*; D011493:Protein Kinase C / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D000077149:Sevoflurane; D013050:Spectrometry, Fluorescence; D013574:Synaptosomes / Q000201:enzymology; D013997:Time Factors
chemical_list: D018685:Anesthetics, Inhalation; D008738:Methyl Ethers; D000077149:Sevoflurane; D007530:Isoflurane; D011493:Protein Kinase C