Endogenous biotin staining in a subset of spinal neuronal cell bodies: a potential confounding factor for neuroanatomical studies.

Biotinylated compounds are commonly used to label neuronal cell bodies via intracellular filling or retrograde tracing. Endogenous concentrations of biotin within a subset of neuronal cell bodies would pose a problem for interpreting such experiments. Here I report that a subset of turtle spinal cord neuronal cell bodies strongly stains for biotin, using the avidin-biotin-horseradish peroxidase (ABC) reaction, in the absence of any exogenous biotinylated compound.