Rapid anterograde movement of the fluorescent tracer Fast Blue: a new method for tracing central connections

Following Fast Blue application to the frontoparietal areas of the cat cerebral cortex on one side, labeled axons, axon collaterals and terminal arborizations could be traced through the 'pyramidal tract' fiber system to all its main areas of termination. Prominent Fast Blue-labeling of axon collaterals and terminals was found in the red nucleus, the pontine nuclei and the cervical level of the spinal gray, as early as 48 h survival time. These observations show that Fast Blue is effectively moved anterogradely through axons and that it can be used as an anterograde tracer to label axonal efferent connections.