Excitation of Squid Giant Axons in Hypotonic and Hypertonic Solutions

Abstract

Excitability of intracellularly perfused squid giant axons was maintained in hypotonic solutions (down to 300 mOSM) and in hypertonic solutions (up to about 10 OSM), when osmolalities of internal and external solutions were adjusted to be equal with glycerol, glucose, or sucrose. Molar concentrations of ions were kept constant during one series of experiments. The resting potential and the amplitude of the action potential did not change in both hypotonic and hypertonic solutions. With reduction of osmolality, the duration of action potential decreased and the maximum rate of rise and conduction velocity increased. By raising osmolality, the duration was prolonged and the maximum rate of rise and the conduction velocity decreased. Effects of osmolality change were almost reversible. However, these effects were not directly related to the osmolality change but seemed to be related to the viscosity change of the solutions. When the osmolality of external solution was raised with NaCl (up to 2.6 M NaCl), the overshoot increased in proportion to the logarithm of the NaCl concentration. The slope of increase was about 50 mV/decade. However, the resting potential showed little change. With increase of the NaCl concentration, the duration of the action potential increased.Physiological experiment with nerves are usually performed in isotonic solutions. An osmolality change in bathing solutions around intact nerves is thought to have some effect on nerves, mainly due to an inflow or an outflow of water across the membrane accompanied with a volume change of cells. Use of isotonic solutions alone limits the range of ionic concentration changes that can be made. Until now, many investigators have examined the excitability of nerves (MULLER-MOHNSSEN and BARSKE, 1974) or muscle (HODGKIN and HOROWICZ, 1957;KAWATA et al., 1974;SUAREZ-KURTZ and SORENSON, 1977) in hypotonic and hypertonic solutions. Since they used intact cells, it was difficult to separate the effect of the intended ionic concentration changes from those of changes in cell volume, in cell surface area and in ionic concentrations inside the cell (FREEMAN et al., 1966;

Properties of sodium and potassium channels of the squid giant axon far below 0°C

“…The concentration of glycerol in the external and the internal solutions was gradually increased, keeping the osmolality of both solutions roughly equivalent in order not to lose the nerve activity (Kukita & Yamagishi, 1979a). The glycerol conentrations (in ~o (vol/vol) of the internal solutions were 10.5, 40.8 and 50.8 and those of the external solutions were 0, 34.2 and 44.2.…”

Percutaneous Adhesiolysis in the Management of Chronic Low Back Pain in Post Lumbar Surgery Syndrome and Spinal Stenosis: A Systematic Review

“…While Hitchcock provided that evidence for the effectiveness of an intrathecal injection of cold saline (236), it was subsequently shown that the efficacy of hypertonic saline was due to the hypertonicity of the solution rather than to any thermal effect (237). Multiple other studies have shown various mechanisms including selective C-fiber blockade in cat dorsal rootlets with an increased concentration of chloride ion (238); decrease of the spinal cord water content and depressed lateral column-evoked ventral root response (174); change in the volume due to outflow of water across the membrane and ionic concentration changes (239); reduction in swelling or by osmotically induced fluid shifts, reducing pressure on the nerve, and producing a local anesthetic effect of the hypertonic solution (240); whereas some have illustrated an actual increase in tissue mass in the case of intravertebral tissue incubated in 10% sodium chloride solution (241). In contrast, Racz and colleagues (242) showed that the study of dural permeability in dogs demonstrated transdural calibration of hypertonic saline to occur very slowly, but resulted in the doubling of the cerebral spinal sodium concentration 20 minutes after extradural placement of 10% sodium chloride solution.…”

One Day Lumbar Epidural Adhesiolysis and Hypertonic Saline Neurolysis in Treatment of Chronic Low Back Pain: A Randomized, Double-Blind Trial

“…In 1969, Hitchcock (53) showed the effectiveness of hypertonic saline was due to the hypertonicity of the solution, instead of any thermal effect. Multiple other effects described include selective C-fiber blockade in cat dorsal rootlets (54), reduction of spinal cord water content and depressed lateral col-umn-evoked ventral root response (55), volume change due to outflow of water across the membrane, and ionic concentration changes producing the effect on axonal function (56). Racz et al (57), in the dural permeability study in dogs demonstrated transdural equilibration of hypertonic saline to occur very slowly, with doubling of cerebrospinal sodium concentration to occur 20 minutes after extradural placement of 10% sodium chloride solution.…”