Bupivacaine Indirectly Potentiates Glutamate-induced Intracellular Calcium Signaling in Rat Hippocampal Neurons by Impairing Mitochondrial Function in Cocultured Astrocytes

Anesthesiology. 2018 Mar;128(3):539-554. doi: 10.1097/ALN.0000000000002003.

Abstract

Background: Bupivacaine induces central neurotoxicity at lower blood concentrations than cardiovascular toxicity. However, central sensitivity to bupivacaine is poorly understood. The toxicity mechanism might be related to glutamate-induced excitotoxicity in hippocampal cells.

Methods: The intracellular free Ca concentration ([Ca]i), mitochondrial membrane potential, and reactive oxygen species generation were measured by fluorescence and two-photon laser scanning microscopy in fetal rat hippocampal neurons and astrocytes.

Results: In astrocyte/neuron cocultures, 300 μM bupivacaine inhibited glutamate-induced increases in [Ca]i in astrocytes by 40% (P < 0.0001; n = 20) but significantly potentiated glutamate-induced increases in [Ca]i in neurons by 102% (P = 0.0007; n = 10). Ropivacaine produced concentration-dependent effects similar to bupivacaine (0.3 to 300 μM). Tetrodotoxin did not mimic bupivacaine's effects. In pure cell cultures, bupivacaine did not affect glutamate-induced increases in [Ca]i in neurons but did inhibit increased [Ca]i in astrocytes. Moreover, bupivacaine produced a 61% decrease in the mitochondrial membrane potential (n = 20) and a 130% increase in reactive oxygen species generation (n = 15) in astrocytes. Cyclosporin A treatment suppressed bupivacaine's effects on [Ca]i, mitochondrial membrane potential, and reactive oxygen species generation. When astrocyte/neuron cocultures were incubated with 500 μM dihydrokainic acid (a specific glutamate transporter-1 inhibitor), bupivacaine did not potentiate glutamate-induced increases in [Ca]i in neurons but still inhibited glutamate-induced increases in [Ca]i in astrocytes.

Conclusions: In primary rat hippocampal astrocyte and neuron cocultures, clinically relevant concentrations of bupivacaine selectively impair astrocytic mitochondrial function, thereby suppressing glutamate uptake, which indirectly potentiates glutamate-induced increases in [Ca]i in neurons.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Anesthetics, Local / pharmacology
  • Animals
  • Astrocytes / drug effects*
  • Bupivacaine / pharmacology*
  • Calcium Signaling / drug effects*
  • Coculture Techniques
  • Female
  • Glutamic Acid / metabolism*
  • Hippocampus / drug effects*
  • Hippocampus / metabolism
  • Male
  • Mitochondria / drug effects*
  • Mitochondria / metabolism
  • Models, Animal
  • Neurons / drug effects
  • Rats
  • Rats, Sprague-Dawley

Substances

  • Anesthetics, Local
  • Glutamic Acid
  • Bupivacaine