Evidence for a vertical displacement of intramembranous particles on the plasma membrane of Tetrahymena cells by a local anesthetic.

We examined the effect of a local anesthetic, dibucaine, on the plasma membrane of Tetrahymena pyriformis strain NT-1 using freeze-fracture electron microscopy. Intramembranous particles (IMPs) were distributed homogeneously on the plasma membrane of untreated cells. But, when Tetrahymena cells had been treated with 1.3 mM dibucaine for 5 min at growth temperature, freeze-fracture micrographs of the plasma membrane showed marked alterations. Although IMPs showed an almost homogeneous distribution, their density was elevated markedly on the protoplasmic fracture (PF) face but greatly reduce on the exoplasmic fracture (EF) face. Areas around deciliated portions had a reverse IMP density distribution for the PF and EF faces. These results suggest that dibucaine induced vertical displacement of the IMPs in the plasma membrane.