Fluro-Gold: composition, and mechanism of uptake

Complex brain circuits studied via simultaneous and permanent detection of three transported neuroanatomical tracers in the same histological section

“…Therefore the search was and is still going on to find even better and more compatible neuroanatomical tracers, detection methods and chromogens than those already at our disposal. Among the currently available transported markers we have selected particularly versatile and stable tracers, notably most promising, the anterogradely transported tracer biotinylated dextran amine (BDA; Veenman et al, 1992;Brandt and Apkarian, 1992;Reiner et al, 1993;Rajakumar et al, 1993;Lanciego and Wouterlood, 1994), the retrogradely transported tracer Fluoro-Gold (FG; Schmued and Fallon, 1986;Schmued and Heimer, 1990;Wessendorf, 1991;Schmued, 1994) and the bi-directionally transported tracer cholera toxin, b subunit (CTB; Stoeckel et al, 1977;Trojanowski et al, 1981Trojanowski et al, , 1982Wan et al, 1982;Ericson and Blomqvist, 1988 (BDA) In retrospect, the introduction of the family of dextran amines as neuroanatomical tracing substances in the mid-1980s (Glover et al, 1986), was a great step forward in neurobiology. The introduction as a tracer by Veenman and co-workers (1992) of the biotinylated derivative (BDA, biotinylated dextran amine) can be considered a breakthrough.…”

“…Because of its excellent and stable fluorescence, simplicity of application, easy reproducibility of the results and many other unique properties, this fluorescent dye has become widely used for tracing neuronal connections (Pieribone and Aston-Jones, 1988;Schmued and Heimer, 1990;Divac and Mogensen, 1990;Wessendorf, 1991;Akintunde and Buxton, 1992;Schmued, 1994;Novikova et al, 1997). Drawbacks with respect to the demands for multiple tracing listed above is that this dye belongs to the family of fluorescent tracers, and that FG is not electrondense in itself and therefore is not very useful in ultrastructural analysis without the help of labor-and time-consuming post-staining processing like photoconversion (Bentivoglio and Su, 1990;Balercia et al, 1992).…”

Behavioral and Anatomical Interactions between Dopamine and Corticotropin-Releasing Factor in the Rat

“…Here, CRF labeling extends more ventrally, almost to the AC (data not shown), suggesting that there is reduced CRF expression on the deposit side caused by necrosis associated with the FG deposit itself (Dado et al, 1990). Although iontophoretic delivery of FG through a glass micropipette with a small tip diameter helps to reduce gross lesion/mechanical disruption effects, it has been reported that the principle mechanism of FG take-up is through damaged fibers (Schmued and Fallon, 1986), although diffusion of FG into nerve terminals or undamaged axons of passage may also be possible (Dado et al, 1990;Wessendorf, 1991). Accordingly, a small lesion such as that indicated in Figure 2 E may actually facilitate retrograde labeling of BSTld afferents.…”

Current concepts in neuroanatomical tracing

“…There, as a lower pH shifts amino groups to the protonised form, the lipophilic membrane becomes impermeable to the now-positively-charged molecules, and they accumulate within these vesicles. Uptake ecacy is determined by the permeability of membranes for the unprotonised form (Wessendorf, 1991). In this way, pH-trapping captures FG, TB, DAPI, NY and several other retrogradely transported molecules.…”

“…Antibodies raised against FG are also available, which means that the dye can be converted into a permanent substrate and that it is possible to plastic embed sections containing FG-labelled tissue without losing the tracer. Despite its excellent tracing properties, FG is not suitable for long-term labelling where survival times of several months are required (Novikova et al, 1997;Schmued and Fallon, 1986;Schmued et al, 1990;Wessendorf, 1991). …”