Increasing extracellular calcium improves conduction in partially demyelinated rat fimbria in vitro

1. We have tested the effect of changed concentrations of Ca2+ upon demyelination-induced conduction block in rat fimbria in vitro. 2. In a rat fimbria containing a region of acute focal demyelination induced by in vitro microinjection of lysophosphatidyl chloride (LPC) 6 days earlier, raising bath [Ca2+] to 4.4 mM improved conduction through the damaged area, while lowering it to 0.25 mM depressed conduction. 3. A contrary effect, consistent with the well-known effects of extracellular calcium ion on voltage-sensitive channels, was seen in non-lesioned preparations.