Effect of volatile anesthetics on Cultured Neuron of Lymnaea stagnalis

2000 Fiscal Year Final Research Report Summary

• Project/Area Number: 11671510
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Anesthesiology/Resuscitation studies
• Research Institution: Miyazaki Medical College
• Principal Investigator: KASABA Toshiharu Miyazaki Medical College, Department of Anesthesiology, Associate Professor, 医学部, 助教授 (80145599)
• Co-Investigator(Kenkyū-buntansha): ONIZUKA Shin Miyazaki Medical College, Department of Anesthesiology, Instructor, 医学部, 助手 (20264393) ; HAMAKAWA Toshiro Miyazaki Medical College, Department of Anesthesiology, Assistant Professor, 医学部, 講師 (50253836)
• Project Period (FY): 1999 – 2000
• Keywords: Lymnaea stagnalis / Respiration / Volatile anesthetics / Sevoflurane / calcium concentration

Research Abstract

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.