The effects of lyotropic anions on electric field-induced guidance of cultured frog nerves.
1. Dissociated Xenopus neurites turn cathodally in small applied electric fields. Increasing the external polycation concentration alters the direction and extent of field-induced orientation. A decrease in membrane surface charge may underlie these effects. 2. Lyotropic anions increase membrane surface charge and we have examined the effect of perchlorate (ClO4-), thiocyanate (SCN-) and sulphate (SO4(2-)) on galvanic nerve orientation. 3. Perchlorate and SCN- had no effect on field-induced cathodal turning, whereas incubation with SO4(2-) was inhibitory. In addition to its effects on surface charge, SO4(2-) increases production of the second messengers diacylglycerol and inositol trisphosphate. Interestingly, lithium (Li+), a blocker of polyphosphoinositide metabolism, had a similar effect to SO4(2-) on field-induced neurite orientation. 4. We conclude that increasing surface charge with lyotropic anions neither enhances galvanotropic orientation nor underlies the inhibitory effects of SO4(2-) and suggest that modulation of galvanotropism by SO4(2-) occurs owing to changes in the inositolphospholipid second messenger system.
Erskine
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Department of Biomedical Sciences, Marischal College, University of Aberdeen, UK.
McCaig
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D000818:Animals; D000838:Anions / Q000494:pharmacology*; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D004574:Electromagnetic Fields; D008051:Lipid Bilayers / Q000737:chemistry*; D008094:Lithium / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects; D016501:Neurites / Q000187:drug effects / Q000502:physiology; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D010472:Perchlorates / Q000737:chemistry / Q000494:pharmacology; D013431:Sulfates / Q000737:chemistry / Q000494:pharmacology; D013861:Thiocyanates / Q000737:chemistry / Q000494:pharmacology; D014982:Xenopus laevis
D000838:Anions; D008051:Lipid Bilayers; D010472:Perchlorates; D013431:Sulfates; D013861:Thiocyanates; D008094:Lithium