Mammalian Non-myelinated Nerve Fibres Research Articles

Active transport and passive fluxes of K, Na, and Li in mammalian non-myelinated nerve fibres.

1. The ionic content of nerve fibres in the rabbit's cervical vagus was measured by flame photometry. Immediately after dissection the intracellular K was 98.0±4.0 and the Na 42.0±2.5 mM/l. Incubation for 5 hr in Locke produced little change in these values. 2. In K-free Locke the fibres lost K and gained Na. The loss of K had a rate constant of 0.0142 min−1, corresponding to an efflux of 0.313 p-mole/cm2·sec. Lowering the pH from 7 to 6 did not affect the efflux of K. 3. The K and Na contents were restored to the initial values within 30 min after addition of 5.6 mM K to the K-free solution. The restoration was inhibited by ouabain. 4. The rate of increase in intracellular K produced by different extracellular concentrations of K indicated a half-maximal activation of the Na-K-pump with 3.8 mM K. 5. Lowering the pH from 7 to 6 increased the half-maximal activation constant to 13.3 mM K, suggesting inhibition of the pump by H+. 6. A study of the effect of intracellular Na suggests that the simultaneous presence of 3–4 Na ions is necessary for activating the internal site of the pump. Half-maximal activation was found with an intracellular Na content of 29.5 mM. 7. Li ions showed a slight activating effect at the external site; their activating effect on the inside was at least 43–44 times smaller than the effect of Na.

Energy-rich metabolites in stimulated mammalian non-myelinated nerve fibres.

Le metabolisme des esters phosphores riches en energie a ete etudie dans des fibres non-myelinisees pendant la periode post-tetanique. Apres une periode de stimulation, le stock d'ATP est utilise dans une proportion de 70%, puis, une rapide resynthese a lieu en 90 sec. On constate egalement une augmentation concommittante de la teneur en ADP. Les pics de degradation de l'ATP et de synthese de l'ADP correspondent approximativement a ceux du degagement de chaleur et de la consommation d'oxygene. Les experiences effectuees avec 2 periodes de stimulation montrent que le contenu en ATP peut s'abaisser a un niveau tres bas. Cette importante diminution suggere une participation possible des cellules de Schwann au metabolisme post-tetanique.

On the electrogenic sodium pump in mammalian non-myelinated nerve fibres and its activation by various external cations.

1. A study has been made of the hyperpolarization that follows a period of electrical activity (the post-tetanic hyperpolarization) in mammalian non-myelinated nerve fibres.2. Evidence is presented that under certain circumstances this postetanic hyperpolarization is a result of activity of an electrogenic sodium pump that normally is absolutely dependent on the external presence of potassium.3. When the external chloride is replaced by sulphate or by isethionate the post-tetanic hyperpolarization, which in normal Locke solution is only a few millivolts in amplitude, is increased usually to about 20 mV, and on occasion to 35 mV.4. This effect of removing the chloride takes several minutes to develop and is consistent with the idea that the increase in the post-tetanic response is the result of removing the short-circuiting effect of internal chloride ions (by their being washed out into the chloride-free bathing medium).5. Small anions, such as chloride, nitrate, iodide, bromide, and thiocyanate can short-circuit the electrogenic pump, whereas larger anions such as sulphate and isethionate cannot. The bicarbonate ion, which is larger than chloride, short-circuits the pump but less effectively.6. In Locke solution containing 5 mM potassium the post-tetanic hyperpolarization declines exponentially, with a time constant of about 1-3 min. The time constant is inversely related to the external potassium concentration.7. However, when the external potassium concentration is zero the hyperpolarization declines rapidly to a very small value. Subsequent addition of potassium to the bathing medium causes a marked redevelopment of the hyperpolarization.8. This potassium-activated response declines exponentially with a time constant that is inversely related to the potassium concentration. When the added potassium concentration is 5 mM, the time constant is 1.9 min.9. The amplitude of the potassium-activated response increases with increasing concentrations of potassium.10. Other cations can produce this activated response. Thus, thallium is more effective than, rubidium as effective as, caesium and ammonium about 1/10 as effective as, and lithium ions about 1/30 as effective as potassium in producing the activated response. Choline is quite ineffective.11. The size of the post-tetanic response is little affected by changes in the duration of the period of stimulation. However, increasing the duration definitely increases the time constant of recovery.12. Reducing the external sodium concentration increases the size of the post-tetanic hyperpolarization (by about 25%), but the effect is complex and requires further study.13. Reducing the calcium of the Locke-solution from 2.2 to 0.2 mM has no appreciable effect on the post-tetanic response, nor has increasing the pH of the Locke from 7.2 to 9.2.14. When the membrane potential is increased or decreased, by externally applied currents, there is relatively little change in the post-tetanic response.15. A mathematical model of the electrogenic pump, devised to mimic the experimental results, was analysed with an analogue computer. A satisfactory agreement between model and experiment was achieved by a model in which: (1) the rate of extrusion of sodium ions depends on the degree to which a pool of carrier molecules on the inside surface of the membrane is combined with sodium; (2) each carrier molecule transfers three sodium ions at a time; (3) the rate constant for extrusion of sodium ions also depends on the presence externally of potassium ions, which combine with some sites on the external surface of the membrane that are half-saturated when the external concentration of potassium is 2.8 mM.

The ionic content of mammalian non-myelinated nerve fibres and its alteration as a result of electrical activity.

1. A study has been made of the ionic content, and of the fibre water, of rabbit desheathed vagus nerves at rest and after activity in various modified Locke solutions.2. In normal Locke solution the intracellular sodium amounted to 86.1 mumole/g dry, and the intracellular potassium 186.0 mumole/g dry. Since the fibre water amounted to 1.124 g/g dry the intracellular sodium and potassium concentrations were 76.6 and 165.5 m-mole/kg fibre water, respectively.3. In potassium-free Locke solution the intracellular sodium and potassium concentrations were 111.0 and 121.7 m-mole/kg, respectively. The intracellular chloride concentration was 40.5 m-mole/kg.4. In normal Locke solution, a brief period of stimulation followed by a 10 min recovery period produced no significant change in the intracellular contents of potassium, sodium, or water.5. However, in chloride-Locke solution from which the potassium had been omitted, or to which ouabain (1 mM) had been added, stimulation caused a loss of potassium per impulse of about 20 p-mole/mg dry, i.e. about 4 p-mole/mg wet. A similar loss was found in isethionate-Locke solution that was potassium-free. There was no significant change in any of the other quantities measured (sodium, chloride, and fibre water).6. The efflux of radioactively labelled potassium was measured in potassium-free Locke solution at rest (k(r)) and during activity (k(s)). At 24 degrees C, k(r) was 0.0084 min(-1) and k(s) was 0.000178 impulse(-1).7. When the chloride of Locke solution was replaced by isethionate there was an increase in both k(r) (about 12%) and k(s) (about 21%).8. Ouabain (1 mM) increased k(s) (by about 70%). This increase seemed to be independent of whether the anion present was chloride or isethionate.9. It is argued that these results indicate that the electrogenicity of the pump plays a relatively small role in maintaining the ionic balance in mammalina C fibres.

THE EFFECT OF THE NERVE SHEATH ON THE ACTION OF LOCAL ANESTHETICS

A comparison has been made of the effect of the nerve sheath on the action of local anesthetics in three different types of nerve fiber preparations, namely, mammalian myelinated, mammalian nonmyelinated and amphibian myelinated nerve fibers. In all types of fiber, alkaline anesthetic solutions were more effective in sheathed preparations, and neutral anesthetic solutions were more effective in desheathed preparations. These results have confinned our earlier conclusion that the cation is the active form of local anesthetics and that the uncharged molecule is important only for penetration to the receptor site.

The oxygen consumption of mammalian non-myelinated nerve fibres at rest and during activity.

1. A study has been made of the oxygen consumption of non-myelinated nerve fibres of rabbit desheathed cervical vagus nerves at rest and during activity.2. The average resting oxygen consumption (Q(r)) was 0.0924 mumole/g. min at 21 degrees C. Stimulation for 1-3 min at 3/sec caused an extra oxygen consumption (Q(s)) of 816 p-mole/g.shock.3. When the frequency of stimulation was increased, to 10/sec and 30/sec, Q(s) fell. When the frequency was decreased, to 1/sec and 0.3/sec, Q(s) increased slightly.4. When the temperature was decreased, Q(r) fell; when the temperature was increased, Q(s) also increased. Temperature similarly affected Q(s) with high frequencies of stimulation, but had relatively little effect on Q(s) at low frequencies of stimulation.5. An isolated single shock seemed to produce an increase in oxygen consumption of about 1200 p-mole/g, and this value was largely independent of temperature.6. When part of the sodium in the Locke solution was replaced by barium, Q(r) decreased (by 12%) whereas Q(s) increased (by 87%).7. Veratrine (1 mug/ml.) increased both Q(r) (by 142%) and Q(s) (by 361%).8. Acetylcholine (1.7 mM) increased Q(r) (by 32%).9. When nerves were transferred to potassium-free solutions there was little change in Q(r), and Q(s) fell slightly (by 8%).10. When the potassium concentration in the Locke solution was increased 4-fold, Q(r) increased (by 27%).11. Salicylate (1-10 mM) increased Q(r) (by 24%) and abolished Q(s).12. When the sodium of Locke solution was replaced by lithium, Q(r) decreased (by 19%) and Q(s) was abolished.13. In sodium-Locke solution ouabain (100 muM) decreased Q(r) (by 26%) and abolished Q(s). In lithium-Locke solution ouabain also decreased Q(r) (by 28%).14. All or nearly all of the oxygen consumed at rest or during activity seemed to be used to pump potassium ions into, and sodium ions out of, the axoplasm.15. The K/O(2) ratio during pumping was about 5.0.

THE INITIAL HEAT PRODUCTION ASSOCIATED WITH THE NERVE IMPULSE IN CRUSTACEAN AND MAMMALIAN NON-MYELINATED NERVE FIBRES.

The Journal of PhysiologyVolume 178, Issue 2 p. 368-383 ArticleFree Access The initial heat production associated with the nerve impulse in crustacean and mammalian non-myelinated nerve fibres B. C. Abbott, B. C. AbbottSearch for more papers by this authorJ. V. Howarth, J. V. HowarthSearch for more papers by this authorJ. M. Ritchie, J. M. RitchieSearch for more papers by this author B. C. Abbott, B. C. AbbottSearch for more papers by this authorJ. V. Howarth, J. V. HowarthSearch for more papers by this authorJ. M. Ritchie, J. M. RitchieSearch for more papers by this author First published: 01 May 1965 https://doi.org/10.1113/jphysiol.1965.sp007633Citations: 24AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Citing Literature Volume178, Issue2May 1, 1965Pages 368-383 RelatedInformation

Metabolic studies on the hyperpolarization following activity in mammalian non-myelinated nerve fibres.

The Journal of PhysiologyVolume 161, Issue 3 p. 414-423 ArticleFree Access Metabolic studies on the hyperpolarization following activity in mammalian non-myelinated nerve fibres P. Greengard, P. GreengardSearch for more papers by this authorR. W. Straub, R. W. StraubSearch for more papers by this author P. Greengard, P. GreengardSearch for more papers by this authorR. W. Straub, R. W. StraubSearch for more papers by this author First published: 01 May 1962 https://doi.org/10.1113/jphysiol.1962.sp006896Citations: 12AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume161, Issue3May 1, 1962Pages 414-423 RelatedInformation

Mammalian nonmyelinated nerve fibers.

Mammalian nonmyelinated nerve fibers.

The action of acetylcholine and some related substances on conduction in mammalian non-myelinated nerve fibres.

The Journal of PhysiologyVolume 155, Issue 2 p. 372-384 ArticleFree Access The action of acetylcholine and some related substances on conduction in mammalian non-myelinated nerve fibres Christine J. Armett, Christine J. ArmettSearch for more papers by this authorJ. M. Ritchie, J. M. RitchieSearch for more papers by this author Christine J. Armett, Christine J. ArmettSearch for more papers by this authorJ. M. Ritchie, J. M. RitchieSearch for more papers by this author First published: 01 February 1961 https://doi.org/10.1113/jphysiol.1961.sp006634Citations: 84AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Citing Literature Volume155, Issue2February 1, 1961Pages 372-384 RelatedInformation

After-potentials in mammalian non-myelinated nerve fibres.

The Journal of PhysiologyVolume 144, Issue 3 p. 442-462 ArticleFree Access After-potentials in mam-malian non-myelinated nerve fibres P. Greengard, P. GreengardSearch for more papers by this authorR. W. Straub, R. W. StraubSearch for more papers by this author P. Greengard, P. GreengardSearch for more papers by this authorR. W. Straub, R. W. StraubSearch for more papers by this author First published: 30 December 1958 https://doi.org/10.1113/jphysiol.1958.sp006112Citations: 45AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume144, Issue3December 30, 1958Pages 442-462 RelatedInformation