Single cell isotope injection technique, a tool for studying axonal and dendritic transport.

Abstract

Radioactive precursors (amino acids and choline) were applied to cat spinal motoneurons by means of micro pipette electrophoresis. The amount injected was determined by the iontophoresis current used. Simultaneous recording of the electrical properties of the nerve cells allowed their identification and the control of the site and effect of injection. At different times after injection (4 min to 3 days) the cats were sacrified by formalin perfusion and autoradiographs were prepared from serial sections of the paraplast embedded spinal cord. This technique provides a high concentration of strictly intracellular radioactivity which is advantageous for the study of intracellular transport. The results indicate that proteins most probably synthetized within the nerve cell soma are transported within the dendrites nearly up to their terminals at a rate of at least 3 mm/h and within the axon at different rates of 0.5 and 1.7 mm/h. Following antidromic stimulation the synthesis of proteins within the nerve cell soma and their export into the axon was increased. Choline derivatives thought to be mainly phospholipids were also transported into dendrites and axon.