Schwann Cell and Axon Electrical Potential Differences

Villegas, Raimundo; Villegas, Leopoldo; Giménez, Máximo; Villegas, Gloria M.

doi:10.1085/jgp.46.5.1047

Cited by 36 publications

(6 citation statements)

References 12 publications

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“…In all cases, the axon membrane potential was continuously monitored. In confirmation of Villegas et al (1963) it was found that a single impulse produces little or no detectable change in membrane potential of the Schwann cell.…”

Section: Estimation Of Cellular Surface Areasmentioning

confidence: 88%

“…The experimental procedure utilized to measure the electrical potential differences across Schwann cell membrane and across the axon membrane was similar to that described and discussed in previous works (Villegas et al 1963;Villegas, Villegas & Gim6nez, 1968).…”

Section: Experimental 8olutto8mentioning

confidence: 99%

“…The Schwann layer of S. sepioidea is 1-5-5 A thick and is formed by a single layer of Schwann cells as described by Villegas et al (1963). The number of Schwann cell nuclei were counted in six nerve fibres.…”

Section: Estimation Of Cellular Surface Areasmentioning

confidence: 99%

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Axon‐schwann cell interaction in the squid nerve fibre

Villegas¹

1972

The Journal of Physiology

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SUEMARYThe electrical properties of Schwann cells and the effects of neuronal impulses on their membrane potential have been studied in the giant nerve fibre of the squid.1. The behaviour of the Schwann cell membrane to current injection into the cell was ohmic. No impulse-like responses were observed with displacements of 35 mV in the membrane potential. The resistance of the Schwann cell membrane was found to be approximately 103 Q2 cm2.2. A long-lasting hyperpolarization is observed in the Schwann cells following the conduction of impulse trains by the axon. Whereas the propagation of a single impulse had little effect, prolonged stimulation of the fibre at 250 impulses/sec was followed by a hyperpolarization of the Schwann cell that gradually declined over a period of several minutes.3. The prolonged effects of nerve impulse trains on the Schwann cell were similar to those produced by depolarizing current pulses applied to the axon by the voltage-clamp technique. Thus, a series of depolarizing pulses in the axon was followed by a long-lasting hyperpolarization of the Schwann cells. In contrast, the application of a series of hyperpolarizing 100 mV pulses at a frequency of 1/sec had no apparent effects.4. Changes in the external potassium concentration did not reproduce the long-lasting effects of nerve excitation.5. The hyperpolarizing effects of impulse trains were abolished by the incubation of the nerve fibre in a sea-water solution containing trypsin.6. These findings are discussed in relation to the possible mechanisms that might be responsible for the long-lasting hyperpolarizations of the Schwann cells.

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Section: Estimation Of Cellular Surface Areasmentioning

confidence: 88%

Section: Experimental 8olutto8mentioning

confidence: 99%

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Axon‐schwann cell interaction in the squid nerve fibre

Villegas¹

1972

The Journal of Physiology

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“…The experimental procedure utilized to measure the electrical potential differences across the Schwann cell membrane and across the axon membrane was similar to that described and discussed in previous works (Villegas, Villegas, Gimenez & Villegas, 1963;Villegas, 1972).…”

Section: General Proceduresmentioning

confidence: 99%

Effects of tubocurarine and eserine on the axon‐Schwann cell relationship in the squid nerve fibre

Villegas¹

1973

The Journal of Physiology

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SUMMARYThe effects of eserine and D-tubocurarine on the axon and Schwann cell membrane potentials have been studied in the giant nerve fibre of the squid.1. The addition of eserine at concentrations of up to 10-4M to the external sea-water medium has no appreciable effects on either the Schwann cell electrical potential of unstimulated nerve fibres or on the resting and action potentials of the axon.2. However, eserine at a concentration of 10-9 M prolongs the longlasting Schwann cell hyperpolarizations which follow the conduction of impulse trains by the axon.3. Higher concentrations of eserine (10-7, 10-4M) decrease and block the long-lasting effects of nerve impulse train conduction.4. D-tubocurarine at concentrations of up to 10-5 M has no appreciable effect on the resting and action potentials of the axon.5. However, D-tubocurarine at a concentration of 10-9 M blocks completely the hyperpolarizing effects of nerve impulse trains on the Schwann cell electrical potential.6. In addition to its blocking action, D-tubocurarine induces transient hyperpolarizations in the Schwann cells of unstimulated nerve fibres both in intact fibres and in slitted preparations.7. These findings suggest that a cholinergic system, which may be located at the axon-Schwann cell boundary, is involved in the genesis of the long-lasting Schwann cell hyperpolarization caused by the conduction of nerve impulse trains by the axon. 7-2

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“…A great deal of electron-microscopic studies have been made on the giant nerve fibers from several species of squid [1,5,10]. Investigation of the ultrastructure of axons from Dosidicus gigas carried out by Villegas [8] stated that the Schwann layer is formed by a single row of Schwann cells crossed by channels.…”

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confidence: 99%

The molecular organization of nerve membranes

et al. 1972

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Plasma membranes were isolated from two types of squid nerves which have morphologically, different ratios of axolemma/Schwannlemma (A/S). These membranes were studied by means of differential and density gradient centrifugation.Thoroughly dissected giant axons were used as membrane source having low A/S ratio. Retinal fibers were used as membrane source with high A/S ratio. A similar procedure for the isolation of the plasma membranes was used for both types of squid axons.Differential centrifugation showed that at 1,500×g, the yield of membrane enzymes (Na, K-ATPase and NADH-ferricyanide oxidoreductase) from giant axon homogenates was 2 to 5 times greater than from retinal nerve homogenates, but at 105,000×g the opposite was the case, the yield from retinal axons being about two times greater. Thus, the major part of the membrane material from the retinal nerve seems to be less dense than the membrane material from giant axons.The behavior of the 105,000×g fraction from both types of fibers was studied by determining protein Na, K-ATPase, and NADH-oxidoreductase along a lineal sucrose gradient (10 to 40%; centrifuged at 40,600×g for 90 min). By any of the three measurements, retinal axons yielded a greater amount (2:1) of plasma membranes sedimenting at low sucrose concentration (16 to 25%) as compared to that observed at high sucrose concentration (35 to 38%). Giant axons, on the contrary, yielded a higher proportion of membranes (2.5:1) sedimenting at high sucrose concentrations (over 40%).The experimental data indicate that a different cellular origin can account for the behavior of nerve membranes along lineal gradient centrifugation. The membranes floating at low sucrose concentration ("light membranes") can be tentatively ascribed to the axolemma; the membranes found at high sucrose concentration ("heavy membranes") to the Schwannlemma and basement membranes.In accord with their high A/S morphological ratio, squid retinal axons yielded 5 times more light membranes (axolemma) than dissected giant axons.

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Schwann Cell and Axon Electrical Potential Differences

Cited by 36 publications

References 12 publications

Axon‐schwann cell interaction in the squid nerve fibre

Axon‐schwann cell interaction in the squid nerve fibre

Effects of tubocurarine and eserine on the axon‐Schwann cell relationship in the squid nerve fibre

The molecular organization of nerve membranes

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