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

• Published in: PloS one Vol. 12; no. 1; p. e0170938
• Main Authors: Shevchouk, Olesya T., Ball, Gregory F., Cornil, Charlotte A., Balthazart, Jacques
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 31.01.2017; Public Library of Science (PLoS)
• Subjects: 17β-Estradiol; Aging - physiology; Analysis; Animals; Biology and Life Sciences; Biomarkers - metabolism; Bird migration; Birds; Brain; Brain - physiology; Bromodeoxyuridine - metabolism; Canaries; Canaries - blood; Canaries - physiology; Cell division; Cell growth; Cell survival; Corticosterone - blood; Deoxyribonucleic acid; Deoxyuridine - analogs & derivatives; DNA; Doublecortin protein; Environmental conditions; Environmental effects; Estradiol; Female; Females; Gender aspects; Gender differences; Hippocampus (Brain); Hormones; Linear Models; Male; Males; Markers; Medicine and Health Sciences; Microtubule-Associated Proteins; Morphology; Neurogenesis; Neuronal Plasticity - physiology; Neurons; Neurons - metabolism; Neuropeptides; Neuroplasticity; Neurosciences; Physiological aspects; Research and Analysis Methods; Sex; Sex Characteristics; Sex differences; Sex differences (Biology); Sex hormones; Social Behavior; Social environment; Song; Song control nuclei; Songbirds; Survival; Testosterone; Thymidine; Ventricle; Ventricular zone; Vocalization, Animal - physiology
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0170938

In songbirds, neurogenesis in the song control nucleus HVC is sensitive to the hormonal and social environment but the dynamics of this process is difficult to assess with a single exogenous marker of new neurons. We simultaneously used three independent markers to investigate HVC neurogenesis in male and female canaries. Males were castrated, implanted with testosterone and housed either alone (M), with a female (M-F) or with another male (M-M) while females were implanted with 17β-estradiol and housed with a male (F-M). All subjects received injections of the two thymidine analogues, BrdU and of EdU, respectively 21 and 10 days before brain collection. Cells containing BrdU or EdU or expressing doublecortin (DCX), which labels newborn neurons, were quantified. Social context and sex differentially affected total BrdU+, EdU+, BrdU+EdU- and DCX+ populations. M-M males had a higher density of BrdU+ cells in the ventricular zone adjacent to HVC and of EdU+ in HVC than M-F males. M birds had a higher ratio of BrdU+EdU- to EdU+ cells than M-F subjects suggesting higher survival of newer neurons in the former group. Total number of HVC DCX+ cells was lower in M-F than in M-M males. Sex differences were also dependent of the type of marker used. Several technical limitations associated with the use of these multiple markers were also identified. These results indicate that proliferation, recruitment and survival of new neurons can be independently affected by environmental conditions and effects can only be fully discerned through the use of multiple neurogenesis markers.