Small iontophoretic injections of the retrograde tracer Fluoro-Gold were restricted to the dorsal columns in the cervical enlargement of 6 rats. Large numbers of neurons were labeled in the lumbosacral dorsal horn in each rat. In the most effective case, more than 1800 neurons were labeled in alternate sections through nine examined segments. Many neurons were also labeled in lumbosacral dorsal root ganglia of all cases. This study, in contrast to previous reports, indicates that Fluoro-Gold can be transported avidly by axons passing through, but not terminating in, injection sites.
Bibliographical noteFunding Information:
Supported by Grant NS25932. R.J.D. was supported in part by DA07234. We thank J.T. Katter for critically reading the manuscript, Ms. C. Andersen and Mr. H. Truong for technical assistance, and Mr. G. Sedgewick for help with photography.
- Dorsal column
- Fiber of passage
- Retrograde tracing