Purpose: Although general anesthetics may decrease neuronal excitation, their detailed effects on spontaneous excitatory postsynaptic currents (EPSCs) remain controversial. We investigated and compared the effects of halothane on N-methyl-D-asparate (NMDA) and non-NMDA receptor-mediated postsynaptic currents.
Methods: Spontaneous synaptic currents were recorded by the patch clamp technique in cultured rat cortical neurons. They were isolated by specific pharmacological blocking agents and their electrophysiologic properties were examined.
Results: The frequency of NMDA EPSCs was preferentially decreased as compared with that of non-NMDA EPSCs at halothane 1.2 mM. The total net charge of EPSCs mediated by NMDA and non-NMDA receptors was depressed to 56% +/- 6% (mean +/- SD) and 71% +/- 7% of control by halothane 0.6 mM, and to 11% +/- 9% and 59% +/- 11% of control by halothane 1.2 mM, respectively.
Conclusion: These results show that halothane causes decrease of excitatory synaptic activity, with NMDA EPSCs being more sensitive than non-NMDA EPSCs.