Neurotrophins Suppress Apoptosis Induced by Deafferentation of an Avian Motor-Cortical Region

Johnson, Frank; Hohmann, Stephen; DiStefano, Peter S.; Bottjer, Sarah W.

doi:10.1523/jneurosci.17-06-02101.1997

Cited by 111 publications

(92 citation statements)

References 60 publications

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“…A more remote, but possible, source of IGF-II peptide in HVC could be the mMAN neurons that project into HVC. This type of orthograde transport has been observed for IGF-I in the olivary -cerebellar system (Nieto-Bona et al, 1993) and for BDN F and N T3 in songbirds (Johnson et al, 1997). Whatever the source, the presence of IGF-II in H VC could protect a subset of RA-projecting cells from cell death while others die and are replaced.…”

Section: Functional Implications Of Igf-ii In Hvcsupporting

confidence: 55%

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Selective Expression of Insulin-Like Growth Factor II in the Songbird Brain

et al. 1997

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Neuronal replacement occurs in the forebrain of juvenile and adult songbirds. To address the molecular processes that govern this replacement, we cloned the zebra finch insulin-like growth factor II (IGF-II) cDNA, a factor known to regulate neuronal development and survival in other systems, and examined its expression pattern by in situ hybridization and immunocytochemistry in juvenile and adult songbird brains. The highest levels of IGF-II mRNA expression occurred in three nuclei of the song system: in the high vocal center (HVC), in the medial magnocellular nucleus of the neostriatum (mMAN), which projects to HVC, and to a lesser extent in the robust nucleus of the archistriatum (RA), which receives projections from HVC. IGF-II mRNA expression was developmentally regulated in zebra finches. In canary HVC, monthly changes in IGF-II mRNA expression covaried with previously reported monthly differences in neuron incorporation. Combining retrograde tracers with in situ hybridization and immunocytochemistry, we determined that the HVC neurons that project to area X synthesize the IGF-II mRNA, whereas the adjacent RA-projecting neurons accumulate the IGF-II peptide. Our findings raise the possibility that within HVC IGF-II acts as a paracrine signal between nonreplaceable area X-projecting neurons and replaceable RAprojecting neurons, a mode of action that is compatible with the involvement of IGF-II with the replacement of neurons. Additional roles for IGF-II expression in songbird brain are likely, because expression also occurs in some brain areas outside the song system, among them the cerebellar Purkinje cells in which neurogenesis is not known to occur.

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Section: Functional Implications Of Igf-ii In Hvcsupporting

confidence: 55%

“…In addition, many of these trophic factors also play a role in the maintenance of the adult nervous system (for review, see Lo, 1995;Thoenen, 1995). Recently, it has been shown that BDNF and NT3 promote the survival of neurons in the developing song system (Johnson et al, 1997).…”

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confidence: 99%

Selective Expression of Insulin-Like Growth Factor II in the Songbird Brain

et al. 1997

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“…In that case, the density of BDNF immunoreactivity was also comparable in the surrounding caudal neostriatum (Johnson et al, 2000). Infusing the protein can prevent neuronal death due to deafferentation in juvenile zebra finches (Johnson et al, 1997), suggesting that it might normally facilitate the increased cell survival in males compared to females. In parallel, we found more trkB-containing cells in the song control nuclei of male than female zebra finches at 30 -60 days of age (Wade, 2000).…”

Section: Summary and Future Directionsmentioning

confidence: 78%

“…TrkB mRNA has also been reported in the HVC, RA, and lMAN of 20 -35-day-old individuals of both sexes (Dittrich et al, 1999). It is clear that BDNF exists in song control nuclei and can be transported among them in an anterograde, and probably retrograde, fashion (Dittrich et al, 1999;Johnson et al, 1997), although the data on its pattern of expression are a bit confusing. In situ hybridization has revealed mRNA in HVC specifically at 30 -35 days of age in males but not females (Dittrich et al, 1999), and cells ventral to HVC at 20 days of age.…”

Section: Summary and Future Directionsmentioning

confidence: 99%

Zebra finch sexual differentiation: The aromatization hypothesis revisited

Wade

2001

Microscopy Res & Technique

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Zebra finches have emerged as an outstanding model system for the investigation of the mechanisms regulating brain and behavior. Their song system has proven especially useful, as the function of discrete anatomical regions have been identified, and striking parallels exist between the morphology of these regions and the level of their function in males and females. That is, the structures are substantially more developed in males, who sing, compared to females, who do not. These parallels extend from higher (telencephalic) centers to the brainstem motor nucleus that innervates the muscles of the vocal organ. Other dimorphic aspects of reproduction in the zebra finch, such as copulatory behaviors and sexual partner preference, however, are not associated with known sex differences in anatomy. In many species, sex differences in neural and peripheral structures and behavior are regulated by secretions from the gonads, which of course are sexually dimorphic themselves. In birds, sex differences at all of these levels (gonad, brain, and behavior) can be mediated by steroid hormones. However, it is not entirely clear that gonadal secretions normally participate at all of the levels. This paper reviews the evidence relating to the role of gonadal steroids in the sexual differentiation of reproductive behaviors and the central and peripheral structures known to regulate them in zebra finches, with a focus on estradiol, which has been most extensively studied in the masculinization of song system morphology and function.

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“…We do not know whether BDNF protein produced during previous days contributed to the basal level seen in our nonsinging birds. Finally, and perhaps most importantly, it is known that much of the BDNF protein produced in one site can be carried away by anterograde transport (47,48). If part of the BDNF protein produced in HVC was transported to RA or Area X, then the amount left in HVC would grossly underestimate the amount produced.…”

Section: Discussionmentioning

confidence: 99%

A relationship between behavior, neurotrophin expression, and new neuron survival

Jarvis

Alvarez-Borda

et al. 2000

Proc. Natl. Acad. Sci. U.S.A.

188

149

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The high vocal center (HVC) controls song production in songbirds and sends a projection to the robust nucleus of the archistriatum (RA) of the descending vocal pathway. HVC receives new neurons in adulthood. Most of the new neurons project to RA and replace other neurons of the same kind. We show here that singing enhances mRNA and protein expression of brain-derived neurotrophic factor (BDNF) in the HVC of adult male canaries, Serinus canaria. The increased BDNF expression is proportional to the number of songs produced per unit time. Singing-induced BDNF expression in HVC occurs mainly in the RA-projecting neurons. Neuronal survival was compared among birds that did or did not sing during days 31-38 after BrdUrd injection. Survival of new HVC neurons is greater in the singing birds than in the nonsinging birds. A positive causal link between pathway use, neurotrophin expression, and new neuron survival may be common among systems that recruit new neurons in adulthood.A set of interconnected brain nuclei referred to as the song system is responsible for song acquisition and production in songbirds. This system includes the high vocal center (HVC), which sends projections to two nuclei, the robust nucleus of the archistriatum (RA), and Area X (Fig. 1). The main motor pathway for song production runs from HVC to RA; RA in turn innervates mesencephalic and medullary nuclei that control respiratory muscles and the bird's vocal organ, the syrinx (1, 2). The projection from HVC to Area X is part of a separate forebrain circuit that is necessary for song learning but not for the production of learned song (3-6).HVC continues to receive new neurons in adulthood, and a majority of these cells project to RA (7-10). The recruitment of new HVC neurons is part of a replacement process, with peaks in cell death in August (midsummer) and January (midwinter), when blood testosterone levels of adult male canaries are low. These peaks in cell death are followed by peaks in new neuron incorporation in October and March, when blood testosterone levels are high (11). Male canaries modify their song in adulthood by adding, dropping, and altering song syllables. Most of these changes occur during the summer and fall, with a secondary wave of change in winter. Song stability is maximal in the spring, when canaries breed and recruitment of new HVC neurons is at its lowest (12). It has been hypothesized that neuronal replacement in HVC provides a cellular basis for the song plasticity observed in adult canaries (11,13).The mechanism that regulates neuronal survival and turnover in HVC has been the focus of two previous studies. These studies suggested that the survival of new HVC neurons can be regulated by testosterone or a testosterone metabolite (14), and the testosterone effect is mediated by the brain-derived neurotrophic factor (BDNF) (15). Specifically, the increase in the recruitment of new HVC neurons after systemic testosterone treatment is blocked by infusing an antibody against BDNF into HVC. Moreover, the effect of testost...

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Neurotrophins Suppress Apoptosis Induced by Deafferentation of an Avian Motor-Cortical Region

Cited by 111 publications

References 60 publications

Selective Expression of Insulin-Like Growth Factor II in the Songbird Brain

Selective Expression of Insulin-Like Growth Factor II in the Songbird Brain

Zebra finch sexual differentiation: The aromatization hypothesis revisited

A relationship between behavior, neurotrophin expression, and new neuron survival

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