Learning from the Axon-Schwann Cell Relationships of the Giant Nerve Fiber of the Squid

2003 ◽  
pp. 95-128 ◽  
Author(s):  
Jorge Villegas
Keyword(s):  
Schwann Cell ◽  
Nerve Fiber

scholarly journals Grayanotoxin, veratrine, and tetrodotoxin-sensitive sodium pathways in the Schwann cell membrane of squid nerve fibers.

1976 ◽  
Vol 67 (3) ◽  
pp. 369-380 ◽  
Author(s):  
J Villegas ◽  
C Sevcik ◽  
F V Barnola ◽  
R Villegas
Keyword(s):  
Membrane Potential ◽  
Cell Membrane ◽  
Schwann Cell ◽  
Nerve Fiber ◽  
Schwann Cells ◽  
Giant Axon ◽  
Nerve Fibers ◽  
Resting Membrane Potential ◽  
External Application ◽  
Axon Membrane

The actions of grayanotoxin I, veratrine, and tetrodotoxin on the membrane potential of the Schwann cell were studied in the giant nerve fiber of the squid Sepioteuthis sepioidea. Schwann cells of intact nerve fibers and Schwann cells attached to axons cut lengthwise over several millimeters were utilized. The axon membrane potential in the intact nerve fibers was also monitored. The effects of grayanotoxin I and veratrine on the membrane potential of the Schwann cell were found to be similar to those they produce on the resting membrane potential of the giant axon. Thus, grayanotoxin I (1-30 muM) and veratrine (5-50 mug-jl-1), externally applied to the intact nerve fiber or to axon-free nerve fiber sheaths, produce a Schwann cell depolarization which can be reversed by decreasing the external sodium concentration or by external application of tetrodotoxin. The magnitude of these membrane potential changes is related to the concentrations of the drugs in the external medium. These results indicate the existence of sodium pathways in the electrically unexcitable Schwann cell membrane of S. sepioidea, which can be opened up by grayanotoxin I and veratrine, and afterwards are blocked by tetrodotoxin. The sodium pathways of the Schwann cell membrane appear to be different from those of the axolemma which show a voltage-dependent conductance.

scholarly journals Sodium, Potassium, and Chloride Concentrations in the Schwann Cell and Axon of the Squid Nerve Fiber

1965 ◽  
Vol 49 (1) ◽  
pp. 1-7 ◽  
Author(s):  
Jorge Villegas ◽  
Leopoldo Villegas ◽  
Raimundo Villegas
Keyword(s):  
Schwann Cell ◽  
Nerve Fiber ◽  
Sucrose Solution ◽  
Sodium Potassium ◽  
Soaking Time ◽  
Cellular Volume ◽  
Cell Concentrations ◽  
Cell Electrolytes ◽  
Zero Time ◽  
Chloride Concentrations

Sodium, potassium, and chloride concentrations were determined in the sheath cells and axoplasm of the nerve fiber of the squid Sepioteuthis sepioidea. The sheaths were obtained by slitting the nerve fiber, the extracellular electrolytes were washed out in isotonic sucrose solution, and the concentrations in the cells were determined after different soaking times in the sucrose solution. Values for the Schwann cell were calculated by extrapolation to zero time from the plots of the logarithms of the concentrations in the cells as a function of soaking time in sucrose solution. The Schwann cells made up 84 per cent of the sheath's total cellular volume. The Schwann cell concentrations in millimols per liter, are: 312 (404-241) for sodium, 220 (308-157) for potassium, and 167 (208-138) for chloride. The concentrations in the axoplasm (mean ± SE), in millimols per liter are: 52 ± 10 for sodium, 335 ± 25 for potassium, and 135 ± 14 for chloride. The possibility that some fraction of the Schwann cell electrolytes, especially of sodium, is bound, cannot be discarded.

Mechanisms of Axon-Schwann Cell Signaling in the Squid Nerve Fiber

1991 ◽  
Vol 633 (1 Glial-Neurona) ◽  
pp. 434-447 ◽  
Author(s):  
PETER D. EVANS ◽  
VINCENZINA REALE ◽  
ROSA MARIA MERZON ◽  
JORGE VILLEGAS
Keyword(s):  
Schwann Cell ◽  
Cell Signaling ◽  
Nerve Fiber

Acetylcholine Synthesis in the Schwann Cell and Axon in the Giant Nerve Fiber of the Squid

1981 ◽  
Vol 36 (2) ◽  
pp. 765-768 ◽  
Author(s):  
Rolf Heumann ◽  
Jorge Villegas ◽  
Daniella W. Herzfeld
Keyword(s):  
Schwann Cell ◽  
Nerve Fiber ◽  
Acetylcholine Synthesis

scholarly journals Autoradiographic localization of acetylcholine receptors in the Schwann cell membrane of the squid nerve fiber

1978 ◽  
Vol 77 (2) ◽  
pp. 371-376 ◽  
Author(s):  
FA Rawlins ◽  
J Villegas
Keyword(s):  
Schwann Cell ◽  
Nerve Fiber ◽  
Acetylcholine Receptors ◽  
Cell Layer ◽  
Nerve Fibers ◽  
Electron Microscope Autoradiography ◽  
Radioactive Label ◽  
Cell Plasma ◽  
Intercellular Channels ◽  
Alpha Bungarotoxin

Intact and slit nerve fibers of the squid Sepioteuthis sepioidea were incubated in a 50-nM solution of [125I] alpha-bungarotoxin in artificial seawater, in the absence and in the presence of D-tubocurarine (10(-4) M). The distribution of the radioactive label was then determined by electron microscope autoradiography. It was found that, in the fibers exposed solely to the radioactive toxin, the label was located mainly at the axon-Schwann cell boundary in the intact nerve fibers or at the axonal edge of the Schwann cell layer in the axon-free nerve fiber sheaths. Label was also present in those regions of the Schwann cell layer rich in intercellular channels. No signs of radioactivity were observed in the nerve fibers exposed to the labeled toxin in the presence of D-tubocurarine. These results indicate that the acetycholine receptors previously found in the Schwann cell plasma membrane are mainly located over the cell surfaces facing the neighboring axon and the adjacent Schwann cells. These findings represent a further advance in the understanding of the relationship between the axon and its satellite Schwann cell.

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