title: Sevoflurane induced suppression of inhibitory synaptic transmission between soma-soma paired Lymnaea neurons.
abstract: The cellular and synaptic mechanisms by which general anesthetics affect cell-cell communications in the nervous system remain poorly defined. In this study, we sought to determine how clinically relevant concentrations of sevoflurane affected inhibitory synaptic transmission between identified Lymnaea neurons in vitro. Inhibitory synapses were reconstructed in cell culture, between the somata of two functionally well-characterized neurons, right pedal dorsal 1 (RPeD1, the giant dopaminergic neuron) and visceral dorsal 4 (VD4). Clinically relevant concentrations of sevoflurane (1-4%) were tested for their effects on synaptic transmission and the intrinsic membrane properties of soma-soma paired cells. RPeD1- induced inhibitory postsynaptic potentials (IPSPs) in VD4 were completely and reversibly blocked by sevoflurane (4%). Sevoflurane also suppressed action potentials in both RPeD1 and VD4 cells. To determine whether the anesthetic-induced synaptic depression involved postsynaptic transmitter receptors, dopamine was pressure applied to VD4, either in the presence or absence of sevoflurane. Dopamine (10(-]5) M) activated a voltage-insensitive K(+) current in VD4. The same K(+) current was also altered by sevoflurane; however, the effects of two compounds were nonadditive. Because transmitter release from RPeD1 requires Ca(2+) influx through voltage-gated Ca(2+) channels, we next tested whether the anesthetic-induced synaptic depression involved these channels. Individually isolated RPeD1 somata were whole cell voltage clamped, and Ca(2+) currents were analyzed in control and various anesthetic conditions. Clinically relevant concentrations of sevoflurane did not significantly affect voltage-activated Ca(2+) channels in RPeD1. Taken together, this study provides the first direct evidence that sevoflurane-induced synaptic depression involves both pre- and postsynaptic ion channels.
authors.affiliation: Respiratory and Neuroscience Research Groups, Faculty of Medicine, The University of Calgary, Calgary, Alberta T2N 4N1, Canada.
authors.forename: T
authors.initials: T
authors.lastname: Hamakawa
authors.forename: Z P
authors.initials: ZP
authors.lastname: Feng
authors.forename: N
authors.initials: N
authors.lastname: Grigoriv
authors.forename: T
authors.initials: T
authors.lastname: Inoue
authors.forename: M
authors.initials: M
authors.lastname: Takasaki
authors.forename: S
authors.initials: S
authors.lastname: Roth
authors.forename: K
authors.initials: K
authors.lastname: Lukowiak
authors.forename: S U
authors.initials: SU
authors.lastname: Hasan
authors.forename: N I
authors.initials: NI
authors.lastname: Syed
mesh_terms: D000200:Action Potentials / Q000187:drug effects* / Q000502:physiology; D018685:Anesthetics, Inhalation / Q000494:pharmacology*; D000818:Animals; D002450:Cell Communication; D002478:Cells, Cultured; D017952:Ganglia, Invertebrate / Q000502:physiology; D008195:Lymnaea; D008738:Methyl Ethers / Q000494:pharmacology*; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D018408:Patch-Clamp Techniques; D000077149:Sevoflurane; D009435:Synaptic Transmission / Q000187:drug effects*
chemical_list: D018685:Anesthetics, Inhalation; D008738:Methyl Ethers; D000077149:Sevoflurane