Abstract
SUMMARYUsing the two electrode voltage clamp configuration, a high voltage activated whole-cell Ca2+ channel current (IBa) was recorded from a cluster of neurosecretory ‘Light Yellow’ Cells (LYC) in the right parietal ganglion of the pond snail Lymnaea stagnalis.Recordings of IBa from LYCs show a reversible concentration-dependent depression of current amplitude in the presence of the volatile anaesthetics halothane, isoflurane and sevoflurane, or the non-volatile anaesthetic pentobarbitone at clinical concentrations.In the presence of the anaesthetics investigated, IBa measured at the end of the depolarizing test pulse showed proportionally greater depression than that at measured peak amplitude, as well as significant decrease in the rate of activation or increase in inactivation or both.Within the range of concentrations used, the concentration-response plots for all the anaesthetics investigated correlate strongly to straight line functions, with linear regression R2 values > 0.99 in all instances.For volatile anaesthetics, the dose-response regression slopes for IBa increase in magnitude, in order of gradient: sevoflurane, isoflurane and halothane, a sequence which reflects their order of clinical potency in terms of MAC value.
Publisher
Cold Spring Harbor Laboratory
Reference52 articles.
1. Mechanism of frequency-dependent broadening of molluscan neurone soma spikes.
2. Calcium Action in Synaptic Transmitter Release
3. The distribution of three wide-acting synaptic inputs to identified neurons in the isolated brain of Lymnaea stagnalis (L.);Comparative Biochemistry and Physiology,1981
4. Chad, J. , Kalman, D. & Armstrong, D. (1987). The role of cyclic AMP-dependent phosphorylation in the maintenance and modulation of voltage activated calcium channels. In Cell calcium and the control of membrane transport, eds. Eaton, D.C. & Mandel, L.J. , pp. 167–186. New York: The Rockefeller Univ. Press.
5. Calcium channel currents in bovine adrenal chromaffin cells and their modulation by anaesthetic agents;Journal of Physiology,1994