ANALYSIS OF THE STEADY-STATE DYNAMICS OF ORGANELLE MOTION IN CULTUREDNEURITES - PUTATIVE INDICATOR OF NEUROTOXIC EFFECT

1. The objective of this study was to develop a physiologically based method to evaluate the neurotoxic potential of drug candidates in vitr o. Rat embryo midbrain cells were grown in micromass culture, and the movement of mitochondria labelled with the fluorescent dye rhodamine 1 23 was quantified in fasciculated neurites, using a laser cytometer. 2 . The rhodamine 123 signal in a defined region of fascicle was quantif ied and photobleached with the laser. A series of post-photobleach sca ns revealed the movement of fluorescent-labelled mitochondria into the bleached region from adjacent unbleached regions. Recovery of fluores cence is a measure of the size of the mobile pool of mitochondria rela tive to the total (moving plus stationary) pool. 3. The steady-state l evels of fluorescence recovery was dependent on intracellular calcium and magnesium concentrations, energy status (ATP), and microtubule int egrity (post taxol or vinblastine treatment). 4. This technique may be a useful indicator of neurotoxic effect.