1,1'-Dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate is a lipophilic dye used to record membrane voltage for fluidity studies. This retrograde stain is useful in staining neurons in vitro and in vivo because the stain is relatively nontoxic to cell bodies and the dye is retained in neurons. In addition, 1,1'-Dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate is an ideal retrograde and anterograde tracer to label the processes as well as the cell bodies of cultured neurons.A dye used to record membrane voltage.