Anesthesia and analgesia.

Abstract : This book is a compendium of the written contributions submitted by the invited speakers to the 40th Annual Meeting of the Society of General Physiologists. There were also 118 abstracts of contributed papers submitted to this meeting, which have been published in the December 1986 issue of The Journal of General Physiology. Partial Contents: Regulation of Cytosolic Free Calcium, The Plasma Membrane in the Control of the Signaling Function of Calcium, Calcium-permeable Channels in Vascular Smooth Muscle: Voltage-activated, Receptor-operated, and Leak Channels, Calcium and Magnesium Movements in Cells and the Role of Inositol Trisphosphate in Muscle, Receptor-mediated Changes in Intracellular Calcium, Mechanisms Involved in Receptor-mediated Changes of Intracellular Ca2 + in Liver, The Role of Phosphatidylinositides in Stimulus-Secretion Coupling in the Exocrine Pancreas, Modulation of Membrane Transport by Intracellular Calcium, The Role of Cyclic AMP-dependent Phosphorylation in the Maintenance and Modulation of Voltage-activated Calcium Channels, Multiple Roles for Calcium and Calcium-dependent Enzymes in the Activation of Peptidergic Neurons of Aplysia, Calcium Involvement in Intracellular Events, The Relationship Between the Cytosolic Free Calcium Ion Concentration and the Control of Pyruvate Dehydrogenase, Membrane and Microfilament Organization and Vasopressin Action in Transporting Epithelia.

Cell calcium and the control of membrane transport : Society of General Physiologists, 40th Annual Symposium : Marine Biological Laboratory, Woods Hole, Massachusetts, 3-7 September, 1986

By using both optical and mechano-electric detectors, we have shown that the squid giant axon swells when an action potential is generated. The maximum swelling is reached at the peak of the action potential. The undershoot of the membrane potential is associated with a marked shrinkage of the axon. We have also demonstrated these mechanical changes in axons from which a major portion of the axoplasm has been removed. We have examined the effects of changing the tonicity of the external medium and of applying several chemical reagents.

Rapid pressure changes and surface displacements in the squid giant axon associated with production of action potentials.

https://www.ecronicon.com/ecne/pdf/ECNE-12-00740.pdf

Mobilization of Intracellular Calcium by the General Anaesthetic Halothane in Cultured, Identified Molluscan Neurons

We have investigated the mechanisms of blockade of calcium channel current by the dihydropyridines, eg nisoldipine, nitrendipine, and nicardipine Membrane current was recorded in isolated calf Purkinje fibers using a two-microelectrode voltage-clamp technique, and voltage protocols were designed to identify voltage- and use-dependent block by these compounds systematically Our results show that calcium channel blockade by dihydropyridine derivatives is strongly modulated by membrane potential Block is more pronounced when current is measured from depolarized holding potentials, but in contrast to verapamil, this voltage-dependent block occurs in the absence of repetitive depolarizations Use-dependent block by dihydropyridines is observed at pulse frequencies greater than 1 Hz Our results suggest that dihydropyridines bind preferentially to the inactivated state of the calcium channel, and that the development of use-dependent block is related to the ionization constants of the compounds Furthermor

Voltage-dependent block of calcium channel current in the calf cardiac Purkinje fiber by dihydropyridine calcium channel antagonists.

O_LIUsing 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. C_LIO_LIRecordings 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. C_LIO_LIIn 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. C_LIO_LIWithin 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. C_LIO_LIFor 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. C_LI

/pdf/a-comparative-study-of-anaesthetic-agents-on-high-voltage-17nqo5yt48.pdf

Terrence J. Morris

Papers

A comparative study of anaesthetic agents on high voltage activated calcium channel currents in identified molluscan neurons