Elsevier

Neuroscience

Volume 85, Issue 2, 8 April 1998, Pages 383-394
Neuroscience

Kinetics of sevoflurane action on GABA- and glycine-induced currents in acutely dissociated rat hippocampal neurons

https://doi.org/10.1016/S0306-4522(97)00637-4Get rights and content

Abstract

Effects of a new kind of volatile anaesthetics, sevoflurane, on GABA- and glycine-gated chloride current (ICl) were examined in single pyramidal neurons acutely dissociated from the rat hippocampal CA1 region, using the voltage-clamp mode of the nystatin-perforated patch-clamp technique. Rapid application of sevoflurane-induced ICl by itself, with the time to peak reduced as the sevoflurane concentration was increased from 10−3 to 3×10−3 M. Although a pretreatment with 10−3 M sevoflurane enhanced the peak amplitude of GABA (3×10−6 M)-induced ICl and suppressed the peak amplitude when the GABA concentration was increased to 10−4 M, the pretreatment decreased the time to peak of the ICl induced by any concentration of GABA (from 3×10−6 to 10−4 M). The treatment also accelerated the decay phase of the GABA-induced ICl. On the other hand, sevoflurane suppressed the peak ICl induced by 3×10−5 M glycine in a concentration-dependent manner. In the presence of 3×10−4 M sevoflurane, the peak amplitude of the glycine-induced ICl was decreased without changes in EC50 or Hill coefficients. Pretreatment with 10−3 M sevoflurane did not affect the time to peak of the ICl induced by any concentration of glycine (from 3×10−5 to 10−3 M). Pretreatment with 3×10−8 M strychnine markedly prolonged the time to peak of the glycine-induced ICl.

These results suggest that sevoflurane modulated the amplitude of the GABA responses, depending on the balance of the accelerated activation and decay phases, and that sevoflurane suppressed the glycine-induced ICl in a non-competitive manner without noticeable effect on the kinetics. The reversible and differential modulation of GABAA and glycine receptors might underlie a part of the anaesthetic actions and less adverse clinical effects of sevoflurane.

Section snippets

Preparation

Pyramidal neurons were acutely dissociated from the CA1 region of the rat hippocampus. Two-week-old Wistar rats (Kyudo, Fukuoka, Japan) were decapitated under pentobarbital anaesthesia (40 mg/kg). The brain was quickly removed from the skull and sliced at a thickness of 400 μm with a microslicer (Dosaka, DTK-1000, Kyoto, Japan). The brain slices were preincubated in an incubation solution bubbled with 95% O2/5% CO2 gas at room temperature for 60 min. Thereafter, slices were treated with pronase (1 

Concentration of sevoflurane in aqueous solutions

To validate our method of dissolving sevoflurane into aqueous solutions, the concentrations of sevoflurane in aqueous solutions were measured using gas chromatography. The linearity of the gas chromatographic readings was confirmed by direct injection of various amounts of sevoflurane stock standard solutions (Fig. 1A). The line represents a linear regression line with a regression coefficient of 0.99. Fig. 1B shows the measured concentrations, plotted against the nominal concentrations

Direct activation of chloride current by sevoflurane

The direct activation of ICl has been shown with various volatile anaesthetics. In cultured rat hippocampal neurons, halothane, isoflurane and enflurane induced the ICl.[42] Similarly, sevoflurane induced the ICl in acutely dissociated hippocampal CA1 pyramidal neurons.[39] The estimated single-channel conductance of sevoflurane-induced ICl was 15.3 pS, close to the main conductance of the GABAA receptor–Cl channel complex.[39] Sevoflurane directly activated the ICl in a concentration-dependent

Acknowledgements

The authors would like to thank Dr T. Ohkura (Maruishi) for the help in measuring the sevoflurane concentrations in aqueous solutions and Dr N. Tokutomi (Kumamoto University) for helpful discussion. This study was supported by Grant-in-Aid for Encouragement of Young Scientists (No. 07770033) to N. Harata from the Ministry of Education, Science and Culture of Japan.

References (42)

  • M.T. Watts et al.

    Gas chromatographic headspace analysis of sevoflurane in blood

    J. Chromat.

    (1992)
  • J. Wu et al.

    Sevoflurane-induced ionic current in acutely dissociated CA1 pyramidal neurons of the rat hippocampus

    Brain Res.

    (1994)
  • T. Yakushiji et al.

    Augmentation of GABA-induced chloride current in frog sensory neurons by diazepam

    Neurosci. Res.

    (1989)
  • N. Akaike et al.

    Nystatin perforated patch recording and its applications to analyses of intracellular mechanisms

    Jap. J. Physiol.

    (1994)
  • Becker C.-M. (1992) Convulsants acting at the inhibitory glycine receptor. In Selective Neurotoxicity (eds Herken H....
  • B.R. Brown et al.

    Whatever happened to sevoflurane?

    Can. J. Anaesth.

    (1992)
  • D.R. Burt et al.

    GABAA receptor subtypes: from pharmacology to molecular biology

    Fedn Am. Socs exp. Biol. J.

    (1991)
  • N.P. Franks et al.

    Molecular and cellular mechanisms of general anaesthesia

    Nature

    (1994)
  • E.J. Frink et al.

    Clinical comparison of sevoflurane and isoflurane in healthy patients

    Anesth. Analg.

    (1992)
  • M.J. Halsey

    A reassessment of the molecular structure–functional relationships of the inhaled general anaesthetics

    Br. J. Anaesth.

    (1984)
  • M. Hara et al.

    Propofol activates GABAA receptor-chloride ionophore complex in dissociated hippocampal pyramidal neurons of the rat

    Anesthesiology

    (1993)
  • Cited by (28)

    • Calcium-induced calcium release in noradrenergic neurons of the locus coeruleus

      2020, Brain Research
      Citation Excerpt :

      Chemical reagents were purchased from Sigma-Aldrich (St. Louis, MO, USA) unless mentioned otherwise. Pharmacological reagents were applied to live neurons by the “Y-tube” method, a fast application system that allows the external solution to be exchanged within 30 msec, with an average travel rate of ~100 μm/msec near the cell (Harata et al., 1996; Harata et al., 1999; Iwabuchi et al., 2013; Kira et al., 1998). This method ensures that all parts of a single neuron are exposed to caffeine within the duration of a single image frame (67 msec).

    • Effects of propofol on glycinergic neurotransmission in a single spinal nerve synapse preparation

      2016, Brain Research
      Citation Excerpt :

      However, the anesthetic concentration tested in many of these studies exceeded clinically relevant concentrations, and therefore it is unclear whether these responses are related to a clinical state of propofol anesthesia. In addition, some previous studies (Hara et al., 1994; Patten et al., 2001) have reported that IGly is not affected by propofol, and one study has shown that sevoflurane suppresses IGly (Kira et al., 1998). These discrepancies in the effects of propofol on IGly may be attributed in part to the different types of subunit compositions in the glycine receptor.

    • Sites of Alcohol and Volatile Anesthetic Action on Glycine Receptors

      2005, International Review of Neurobiology
      Citation Excerpt :

      In the same way, volatile anesthetics have been shown to potentiate GlyRs. Experiments have shown that volatile anesthetics enhance glycine‐activated chloride currents of GlyRs in rat medullary neurons (Downie et al., 1996), dissociated rat hippocampal neurons (Kira et al., 1998), as well as in recombinant systems with transiently transfected cells (Harrison et al., 1993) and in Xenopus oocytes (Downie et al., 1996). Analysis of current data showed that the GlyR is one of the most credible candidates for mediating immobility caused by volatile anesthetics (Sonner et al., 2003).

    View all citing articles on Scopus
    View full text