Lidocaine, a local anesthetic, reversibly inhibits cytoplasmic Streaming inVallisneria mesophyll cells

Abstract

Lidocaine, which like other local anesthetics is known to inhibit intracellular transport in animal cells, was tested for its effect on the rotational cytoplasmic streaming in the mesophyll cells of the aquatic plantVallisneria. The drug caused reversible inhibition of cytoplasmic streaming in a dose dependent manner within the 2–20 mM range; higher concentrations resulted in permanent cessation of all cytoplasmic motion. Upon recovery following replacement of the normal bathing medium, cytoplasmic rotation was always resumed in the direction of the original movement exhibited by a given cell. The lidocaine effect was virtually independent of the ionic composition of the incubation medium, but it was markedly affected by the external pH; acidic conditions (pH 6) largely prevented the inhibition of streaming, whereas an alkaline environment (pH 8) accelerated both the onset of the effect and the recovery upon removal of the anesthetic. On the basis of these results and findings in other systems, it is suggested that lidocaine acts through interference with mechanisms that regulate cytoplasmic streaming, rather than with the motile apparatus or the supply of metabolic energy.