Combined light and electron microscopic tracing of neurons, including axons and synaptic terminals, after intracellular injection of horseradish peroxidase.

By using intracellular deposition of horseradish peroxidase (HRP), a method has been designed for combined light and electron microscopic tracing of single fibers and synaptic terminals, belonging to physiologically characterized neurons. This technique has been successfully tested on the axon collateral systems of cat alpha-motoneurons, but should also be applicable to other types of neurons.