Seasonal changes in astrocytes parallel neuronal plasticity in the song control area HVc of the canary

Abstract

In the song control area HVc of the canary, intercellular dye-coupling among astrocytes was studied by intracellular injection of neurobiotin into identified single astrocytes. Injection of individual astrocytes into acute slices resulted in dye spread to neighboring astrocytes, covering a sphere of up to 1 mm in diameter. The astrocytic nature of the dye-coupled cells was verified by double labeling of neurobiotin-filled cells with antisera for the astrocytic filament proteins GFAP or vimentin. The similarity in the number of dye-coupled cells and the total number of astrocytes labeled by immunocytochemical markers indicate that dye-coupling is specific for astrocytes and labels almost the entire local astrocytic population. Within the major nucleus for vocal control (HVc), approximately 25% more astroglial cells were present than in the surrounding forebrain tissue. There is no apparent hindrance of dye spread at the border of the HVc. The density of dye-coupled astrocytes and the expression of cytoskeletal filament proteins differed markedly between the reproductive period in spring and the quiescent period in autumn. While vimentin is the major astroglial filament in autumn, GFAP is strongly expressed in spring. The density of dye-coupled astrocytes reveals a marked increase in the reproductive period, followed by a reduction in autumn. The data indicate that the astrocytic population in the avian forebrain undergoes significant changes coincident with the known functional changes in the vocal control nuclei during periods of song production.

Effects of Cortical Ischemia and Postischemic Environmental Enrichment on Hippocampal Cell Genesis and Differentiation in the Adult Rat

“…Astrocytes are important mediators of environmentally induced plasticity. They increase in number and contact with synaptic elements in rats reared in a complex environment (Diamond et al, 1966;Walsh, 1969;Jones and Greenough, 1996;Sirevaag and Greenough, 1991), and seasonal changes in astrocytes parallel neuronal plasticity in the song control area of the canary (Kafitz et al, 1999). The environmental promotion of gliogenesis observed in our study is in line with these data.…”

Evaluating the predictive value of doublecortin as a marker for adult neurogenesis in canaries (Serinus canaria)

“…As part of the song control circuit, nucleus HVC is well known for its seasonally regulated plasticity in terms of overall morphology and cellular cytoarchitecture, as well as for its capacity to incorporate new RAprojecting neurons in adulthood (Nottebohm, 1981;Alvarez-Buylla et al, 1988;Gahr, 1990;Kirn et al, 1994;Kafitz et al, 1999;Balthazart et al, 2008). In our study, we observed clear DCX immunoreactivity in RA-projecting neurons in nucleus HVC (Fig.…”

Vocal motor experiences consolidate the vocal motor circuitry and accelerate future vocal skill development

“…The seasonal development and degradation in vocal performance are highly correlated with changes in testosterone levels (14)(15)(16)(17), and are often accompanied by gross anatomical and cytoarchitectural restructuring of the brain areas involved in song production (18)(19)(20)(21)(22)(23)(24). Thus testosterone-regulated adaptations of the songbird brain may play an important role in optimizing song performance.…”