FluoroGold

Fluoro-Gold is a fluorescent retrograde tracer commonly used in neuroscience to map neural connections. When injected into a target region, Fluoro-Gold is taken up by axon terminals and transported back to the neuronal cell bodies, labeling the neurons that project to the injection site. This retrograde transport allows researchers to identify afferent inputs to specific brain regions or spinal cord segments.

In practice, Fluoro-Gold produces bright, stable labeling that is detectable with standard fluorescence microscopy. It is typically excited with near-ultraviolet or blue light and emits a yellow-green fluorescence, making labeled neurons stand out against the surrounding tissue. Its robust signal and relatively simple application have made it a long-standing tool for tracing projections across neural circuits in a variety of species.

Applications of Fluoro-Gold include mapping corticofugal, thalamocortical, brainstem, and spinal projections, as well as exploring connectivity patterns in sensory and motor pathways. It is often used in combination with other tracers to distinguish overlapping projection systems or to perform dual-labeling experiments.

Limitations of Fluoro-Gold include its status as a purely retrograde tracer, meaning it labels cell bodies of projecting neurons but does not provide information about downstream synaptic targets. Injection quality and spread can influence labeling specificity, and there is potential for uptake by damaged fibers or non-specific labeling in some conditions. As a research chemical, Fluoro-Gold is typically used in animal studies under appropriate ethical approvals and lab safety protocols.