Abstract
In the current study, we examined for the first time, the potential for adult neurogenesis throughout the brain of the Congo African grey parrot (Psittacus erithacus) and Timneh grey parrot (Psittacus timneh) using immunohistochemistry for the endogenous markers proliferating cell nuclear antigen (PCNA), which labels proliferating cells, and doublecortin (DCX), which stains immature and migrating neurons. A similar distribution of PCNA and DCX immunoreactivity was found throughout the brain of the Congo African grey and Timneh grey parrots, but minor differences were also observed. In both species of parrots, PCNA and DCX immunoreactivity was observed in the olfactory bulbs, subventricular zone of the lateral wall of the lateral ventricle, telencephalic subdivisions of the pallium and subpallium, diencephalon, mesencephalon and the rhombencephalon. The olfactory bulb and telencephalic subdivisions exhibited a higher density of both PCNA and DCX immunoreactive cells than any other brain region. DCX immunoreactive staining was stronger in the telencephalon than in the subtelencephalic structures. There was evidence of proliferative hot spots in the dorsal and ventral poles of the lateral ventricle in the Congo African grey parrots at rostral levels, whereas only the dorsal accumulation of proliferating cells was observed in the Timneh grey parrot. In most pallial regions the density of PCNA and DCX stained cells increased from rostral to caudal levels with the densest staining in the nidopallium caudolaterale (NCL). The widespread distribution of PCNA and DCX in the brains of both parrot species suggest the importance of adult neurogenesis and neuronal plasticity during learning and adaptation to external environmental variations.
Highlights
Adult neurogenesis encompasses the birth and maturation of new neurons that become incorporated into existing circuitry or replace old and damaged neurons under normal physiological and or pathological conditions (Lindsey and Tropepe, 2006)
We examined putative adult neurogenesis throughout the brains of the Congo African grey parrot (Psittacus erithacus) and the Timneh grey parrot (Psittacus timneh) using immunohistochemical techniques for the endogenous markers proliferating cell nuclear antigen (PCNA) and DCX
PCNA and DCX immunoreactivity was observed in the layers of the olfactory bulbs (OBs), the subventricular zone (SVZ) of the lateral, third and fourth ventricles and the cerebral aqueduct, subdivisions of the pallium (Hp, hyperpallium apicale (HA), hyperpallium intercalatus (HI), hyperpallium densocellulare (HD), M, N, E, and A), subpallium (MSt, lateral striatum (LSt), medial septum (SM), and lateral septum (SL)), diencephalon, mesencephalon, and rhombencephalon
Summary
Adult neurogenesis encompasses the birth and maturation of new neurons that become incorporated into existing circuitry or replace old and damaged neurons under normal physiological and or pathological conditions (Lindsey and Tropepe, 2006). The process of adult neurogenesis was confirmed in a variety of species from different taxa ranging from insects to humans This process has been confirmed in wide spectrum of species, the animals studied to date represent only a small fraction of the extant species, and studying further species will allow a broader understanding of the potential diversity of the process and function of adult neurogenesis (Barnea and Pravosudov, 2011). The rate of adult neurogenesis decreases with age across vertebrate taxa (Kuhn et al, 1996; Knoth et al, 2010; Amrein et al, 2011; LaDage et al, 2011; Ngwenya et al, 2017), and the process is affected by factors such as genetics, endogenous and exogenous factors, and seasonal variation (for a review, see Barnea and Pravosudov, 2011)
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