Abstract
Neurogenesis in the adult brain appears to be phylogenetically conserved across the animal kingdom. In pigeons and other adult non-oscine birds, immature neurons are observed in several prosencephalic areas, suggesting that neurogenesis may participate in the control of different behaviors. The mechanisms controlling neurogenesis and its relevance to defensive behaviors in non-oscine birds remain elusive. Herein, the contribution of the environment to behavior and neurogenesis of pigeons was investigated. Adult pigeons (Columba livia, n = 6/group), housed in standard (SE) or enriched environment (EE) for 42 days, were exposed to an unfamiliar environment (UE) followed by presentation to a novel object (NO). Video recordings of UE+NO tests were analyzed and scored for latency, duration and frequency of angular head movements, peeping, grooming, immobility and locomotion. Twenty-four hours later, pigeons were submitted to the tonic immobility test (TI) and number of trials for TI and TI duration were scored, followed by euthanasia 2 h later. Brains were immunohistochemically processed to reveal doublecortin (DCX), a marker for newborn neurons. Compared to those housed in SE, the pigeons housed in EE responded to a NO with more immobility. In addition, the pigeons housed in EE presented longer TI, more DCX-immunoreactive (DCX-ir) cells in the hippocampus and fewer DCX-ir cells in the lateral striatum than those housed in SE. There was no correlation between the number of DCX-ir cells and the scores of immobility in behavioral tests. Together, these data suggest that enrichment favored behavioral inhibition and neurogenesis in the adult pigeons through different, parallel mechanisms.
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Abbreviations
- A:
-
Arcopallium
- AHM:
-
Angular head movements
- BSA:
-
Bovine serum albumin
- CDL:
-
Area corticoidea dorsolateralis
- DAB:
-
3,3'-Diaminobenzidine
- DCX:
-
Doublecortin
- DCX-ir:
-
Doublecortin immunoreactive
- DG:
-
Dentate gyrus
- DL:
-
Dorsolateral region of Hp
- DM:
-
Dorsomedial region of Hp
- E:
-
Entopallium
- EE:
-
Enriched environment
- Ep:
-
Ependyma
- GP:
-
Globus pallidus
- HA:
-
Hyperpallium apicalle
- HD:
-
Hyperpallium densocellulare
- Hp:
-
Hippocampus
- HVC:
-
Higher vocal center
- ief:
-
Intraependymal DCX-ir fascicles
- ll:
-
Lateral layer of ‘‘V’’-shaped Hp area
- LPS:
-
Lamina pallio-subpallialis
- LSt:
-
Lateral striatum
- ml:
-
Medial layer of ‘‘V’’-shaped Hp area
- MSt:
-
Medial striatum
- M:
-
Mesopallium
- N:
-
Nidopallium
- NO:
-
Novel object
- PB:
-
Phosphate buffer
- PBS:
-
Phosphate buffer saline solution
- PBST:
-
PBS plus 0.25 % triton X-100
- RA:
-
Robustus arcopallii
- rmb:
-
Rostral migratory-like bundle of DCX-ir fibers
- SE:
-
Standard environment
- SGZ:
-
Subgranular layer
- St:
-
Striatum
- SVZ:
-
Subventricular zone
- TI:
-
Immobility test
- TPO:
-
Area temporoparieto-occipitalis
- Tr:
-
Triangular part of ‘‘V’’-shaped Hp area
- UE:
-
Unfamiliar environment test
- UE+NO:
-
Unfamiliar environment test plus novel object test
- VP:
-
Ventral pallidum
- V:
-
Lateral ventricle
- VZ1 or 2:
-
Ventricular proliferative zones 1 or 2
- VZ:
-
Ventricular zone
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Acknowledgments
Michele Vaz Pinheiro (MVP) and Fernando Falkenburger Melleu (FFM) have contributed equally to the development, data collection and analysis of the present experiments and both should be considered the main authors of the present report. The present study was supported by FAPESC (‘‘Young Investigator Grants’’) and Alexander von Humboldt Foundation Research (‘‘Equipment Grants’’) to CLO, as well as by CNPq Research Grants to JMN (proc. 471888/03-6 and 300308/2007-8). FFM and MVP received CAPES MSc fellowships. We wish to thank the excellent and devoted technical help and animal care provided by Mr. Carlos H. Espíndola, Mrs. Joanésia M. J. Rothstein, Mr. Marco A. de Lorenzo, Mr. Emerson V. Fornalski, Mrs. Sandra R. B. de Oliveira, and Mr. Sandro M. de Jesus throughout the experiments.
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All authors contributed to this work and gave their consent to publish this paper. We do not have any commercial conflicts of interest. All financial support came from public agencies without any influence on study design, collection, analysis, and interpretation of data or writing of reports. We guarantee all animal procedures were conducted in compliance with “Guidelines for the Care and Use of Mammals in Neuroscience and Behavioral Research” and the protocols were approved by the Local Ethical Committee in Animal Research. We also guarantee that this work is not under simultaneous consideration in any other journal and will not be published elsewhere in any language without the consent of the copyright owners, that the rights of third parties will not be violated and that the publisher will not be held legally responsible should there be any claims for compensation.
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Melleu, F.F., Pinheiro, M.V., Lino-de-Oliveira, C. et al. Defensive behaviors and prosencephalic neurogenesis in pigeons (Columba livia) are affected by environmental enrichment in adulthood. Brain Struct Funct 221, 2287–2301 (2016). https://doi.org/10.1007/s00429-015-1043-6
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DOI: https://doi.org/10.1007/s00429-015-1043-6