The Cell Birth Marker BrdU Does Not Affect Recruitment of Subsequent Cell Divisions in the Adult Avian Brain

Abstract

BrdU is commonly used to quantify neurogenesis but also causes mutation and has mitogenic, transcriptional, and translational effects. In mammalian studies, attention had been given to its dosage, but in birds such examination was not conducted. Our previous study suggested that BrdU might affect subsequent cell divisions and neuronal recruitment in the brain. Furthermore, this effect seemed to increase with time from treatment. Accordingly, we examined whether BrdU might alter neurogenesis in the adult avian brain. We compared recruitment of [3H]-thymidine+ neurons in brains of zebra finches (Taeniopygia guttata) when no BrdU was involved and when BrdU was given 1 or 3 months prior to [3H]-thymidine. In nidopallium caudale, HVC, and hippocampus, no differences were found between groups in densities and percentages of [3H]-thymidine+ neurons. The number of silver grains per [3H]-thymidine+ neuronal nucleus and their distribution were similar across groups. Additionally, time did not affect the results. The results indicate that the commonly used dosage of BrdU in birds has no long-term effects on subsequent cell divisions and neuronal recruitment. This conclusion is also important in neuronal replacement experiments, where BrdU and another cell birth marker are given, with relatively long intervals between them.

Artificial Light at Night Increases Recruitment of New Neurons and Differentially Affects Various Brain Regions in Female Zebra Finches

“…We counted BrdU + neurons in NC, HC, and MSt (see Figure 7 A). To determine the boundaries of NC and HC, as well as the locations of the five sections that were sampled along the rostro-caudal axis in each of these brain regions, we followed our previous protocol as described in [ 56 ]. Those of MSt were determined according to [ 52 ] ( Figure 7 B–D).…”

Active immunization against vasoactive intestinal polypeptide decreases neuronal recruitment and inhibits reproduction in zebra finches

“…As the NC is a large brain region, in each section that was mapped, we scanned about 35% of the whole NC area in that section, recorded the location of BrdU + neurons, and counted them. Scanning 35% of the NC area is based on previous evaluation from our laboratory, i.e., that mapping this portion yields results equivalent to mapping the entire area of the NC in the section (Cattan et al, ). This was obtained by using the fractionator probe in our mapping system, which randomly chose sampling squares (each of an area of 10,000 µm 2 ; 150–400 squares/section, depending on the area of the NC in each section).…”

Studies of HVC Plasticity in Adult Canaries Reveal Social Effects and Sex Differences as Well as Limitations of Multiple Markers Available to Assess Adult Neurogenesis

“…Traditionally neurogenesis is studied with the use of one of two thymidine analogues, [ 3 H]-thymidine or 5-bromo-2’-deoxyuridine (BrdU) and there are a few cases when these two markers have been combined in the same study (see [ 13 ] for an example in birds). More recently endogenous markers that label specific phases in proliferation and neuroblast development have also been used.…”

“…We complemented this approach with a quantification of the endogenous marker of newborn neurons, DCX. Previous studies in mammals and birds have combined the use of two markers for labeling new neurons (e.g., [ 13 , 53 , 54 ], see [ 14 ] for discussion) but this is to our knowledge the first time that two exogenous and one endogenous marker are used simultaneously, in particular for analyzing neurogenesis in the songbird HVC, a model system characterized by a very intense neurogenesis (much more active than in the mammalian hippocampus) that provides more sensitive measures of changes in the neurogenesis process.…”