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

Villegas, Jorge

doi:10.1113/jphysiol.1973.sp010264

Cited by 47 publications

(27 citation statements)

References 10 publications

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“…Giant axons with their surrounding Schwann-cell sheath were then isolated and cleaned of adhering bundles of small nerve fibres by dissection in artificial sea water (see below). Electrophysiological techniques were as described previously and involved the successive measurement of electrical potentials of a series of Schwann cells by brief impalements from inside the axon (Villegas, 1972(Villegas, , 1973(Villegas, , 1975. All experiments were carried out at room temperature (20-22 0C).…”

Section: Methodsmentioning

confidence: 99%

Peptidergic modulation of the membrane potential of the Schwann cell of the squid giant nerve fibre.

Evans¹,

Reale²,

Villegas³

1986

The Journal of Physiology

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SUMMARY1. The effects of a range of neuropeptides were investigated on the membrane potential of the Schwann cells of the giant nerve fibre of the tropical squid.2. Vasoactive intestinal peptide (VIP) produced a dose-dependent, long-lasting hyperpolarization of the Schwann-cell membrane potential. Among peptides structurally related to VIP, similar effects were produced by peptide histidine isoleucine (PHI) but not by secretin and glucagon. 4. VIP produces its effects on the Schwann-cell membrane potential via a receptor system that is independent from those described previously which mediate the effects of carbachol and DL-octopamine. However, VIP can potentiate the effects of the latter systems.5. The actions of VIP on the Schwann cell are unlikely to be mediated via changes in adenosine 3',5'-cyclic monophosphate (cyclic AMP) levels and are insensitive to changes in the level of extracellular calcium in the superfusate. The actions of VIP are, however, potentiated in the presence of low concentrations of lithium ions suggesting that the VIP receptor may mediate its effects by inducing the hydrolysis of polyphosphatidylinositols in the Schwann-cell membrane.6. Evidence is presented for the existence of an endogenous VIP-like component in the normal hyperpolarizing action ofgiant-axon activity on the membrane potential of the Schwann cell.

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Section: Methodsmentioning

confidence: 99%

Peptidergic modulation of the membrane potential of the Schwann cell of the squid giant nerve fibre.

Evans¹,

Reale²,

Villegas³

1986

The Journal of Physiology

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“…This possibility is made even more intriguing by the observation that the adaxonal glial cells of the giant axon are hyperpolarized by axonal action potentials and that this hyperpolarization may be mediated by aeetylcholine (68,69). Fischer and Litvak (16) measured the effects of a brief period of stimulation on amino acid incorporation into giant fibers.…”

Section: Modulation Of Local Axonal Protein Synthesis and Transfermentioning

confidence: 99%

Cell-to-cell transfer of glial proteins to the squid giant axon: The glia- neuron protein transfer hypothesis

Lasek¹,

Gainer²,

Barker³

1977

The Journal of Cell Biology

186

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The hypothesis that glial cells synthesize proteins which are transferred to adjacent neurons was evaluated in the giant fiber of the squid (Loligo pealei). When giant fibers are separated from their neuron cell bodies and incubated in the presence of radioactive amino acids, labeled proteins appear in the glial cells and axoplasm. Labeled axonal proteins were detected by three methods: extrusion of the axoplasm from the giant fiber, autoradiography, and perfusion of the giant fiber. This protein synthesis is completely inhibited by puromycin but is not affected by chloramphenicol. The following evidence indicates that the labeled axonal proteins are not synthesized within the axon itself. (a) The axon does not contain a significant amount of ribosomes or ribosomal RNA. (b) Isolated axoplasm did not incorporate [aH]leucine into proteins. (c) Injection of RNase into the giant axon did not reduce the appearance of newly synthesized proteins in the axoplasm of the giant fiber. These findings, coupled with other evidence, have led us to conclude that the adaxonal glial cells synthesize a class of proteins which are transferred to the giant axon. Analysis of the kinetics of this phenomenon indicates that some proteins are transferred to the axon within minutes of their synthesis in the glial cells. One or more of the steps in the transfer process appear to involve Ca ++, since replacement of extracellular Ca ++ by either Mg § or Co §247 significantly reduces the appearance of labeled proteins in the axon. A substantial fraction of newly synthesized glial proteins, possibly as much as 40%, are transferred to the giant axon. These proteins are heterogeneous and range in size from 12,000 to greater than 200,000 daltons. Comparisons of the amount of amino acid incorporation in glia cells and neuron cell bodies raise the possibility that the adaxonal glial cells may provide an important source of axonal proteins which is supplemental to that provided by axonal transport from the cell body. These findings are discussed with reference to a possible trophic effect of glia on neurons and metabolic cooperation between adaxonal glia and the axon.It has often been suggested that adjacent cells communicate with one another via the actual intercellular transfer of molecules including macromolecules. The possibility that molecular transfer may play a role in intercellular regulation has taken on added credibility since the discovery and

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“…The close apposition of the axon and Schwann cell plasma membranes at the site of the structural complex poses the question of whether these specialized zones are also related to the functional interaction between the axon and the Schwann cell that has been already described in squid giant nerve fibers (29) and that seems to be mediated by a cholinergic system (30,31). In this way, the structural complexes may be related to the so-called gap junctions (18) which represent the morphological correlates for the low resistance junctions that serve as sites of electrotonic coupling between cells (14).…”

Section: Villegas and Villegas Glycoside-sensitive Structures In Squimentioning

confidence: 99%

Structural complexes in the squid giant axon membrane sensitive to ionic concentrations and cardiac glycosides

Villegas¹,

Villegas²

1976

The Journal of Cell Biology

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Giant nerve fibers of squid Sepioteuthis sepioidea were incubated for 10 min in artificial sea water (ASW) under control conditions, in the absence of various ions, and in the presence of cardiac glycosides. The nerve fibers were fixed in OsO, and embedded in Epon, and structural complexes along the axolemma were studied. These complexes consist of a portion of axolemma exhibiting a three-layered substructure, an undercoating of a dense material (~0.1 #m in length and ~70-170 ,/~ in thickness), and a narrowing to disappearance of the axon-Schwann cell interspace. In the controls, the incidence of complexes per 1,000 #m of axon perimeter was about 137. This number decreased to 10-25% when magnesium was not present in the incubating media, whatever the calcium concentration (88, 44, or 0 raM). In the presence of magnesium, the number and structural features of the complexes were preserved, though the number decreased to 65% when high calcium was simultaneously present. The complexes were also modified and decreased to 26-32% by incubating the nerves in solutions having low concentrations of sodium and potassium. The adding of 10 -5 M ouabain or strophanthoside to normal ASW incubating solution decreased them to 20-40%. Due to their sensitivity to changes in external ionic concentrations and to the presence of cardiac glycosides, the complexes are proposed to represent the structural correlate of specialized sites for active ion transport, although other factors may be involved.

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

Cited by 47 publications

References 10 publications

Peptidergic modulation of the membrane potential of the Schwann cell of the squid giant nerve fibre.

Peptidergic modulation of the membrane potential of the Schwann cell of the squid giant nerve fibre.

Cell-to-cell transfer of glial proteins to the squid giant axon: The glia- neuron protein transfer hypothesis

Structural complexes in the squid giant axon membrane sensitive to ionic concentrations and cardiac glycosides

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