Effect of volatile anesthetics on Cultured Neuron of Lymnaea stagnalis

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The cellular and synaptic mechanisms by which general anesthetics affect cell-cell communications in the nervous system remain poorly defined. Inhibitory synapses were reconstructed in cell culture, between the somata of two functionally well-characterized neurons, right pedal 1 (RPeD1) 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 postosynaptic potentials in VD4 were completely and reversibly blocked by sevoflurane (4%). Sevoflurane also suppressed action potentials in both RPeD1 and VD4 cells.To clear the mechanism in [Ca^<2+>]i produced by clinically relevant concentration of volatile anesthetics, we measured [Ca^<2+>]i and intracellular recording simultaneously using a cultured neuron of Lymnaea stagnalis. The RPeD1 neurons were dissected from snails. Anesthetic-induced change in [Ca^<2+>]i were measured with fura-2 fluorescence spectroscopy. The concentration of 1% and 4% were evaluated. To neglect the action potential, we hyperpolarized the membrane potential 10mV and the same measurements were repeated. Sevoflurane 1% increased [Ca^<2+>]i from 325±7 (nM±SD) to 350±8, with the increasing of the number of action potentials to 30±12 (/min±SD) in RPeD1 neurons. Sevoflurane 4%, first increased [Ca^<2+>]i from 330±41 to 380±35 with the increasing to 50±5, in which [Ca^<2+>]i decreased gradually and the number of action potentials decreased to 0 rapidly. Sevoflurane, without activation, increase [Ca2+]i from 320±32 to 332±32 in 1%, and no change from 332±19 to 341±17 in 4%. We concluded that low concentration of sevoflurane increase [Ca^<2+>]i both with and without the activation of the RPeD1 neuron of Lymnaea stagnalis, while high concentration of sevoflurane d [Ca^<2+>]i from the increasing level.