Visualization of Rostral Migratory Stream in the Developing Rat Brain by In Vivo Electroporation

Food for Thought: The Effects of Feeding on Neurogenesis in the Ball Python, Python regius

INTRODUCTION

Pythons are a well-studied model of postprandial physiological plasticity. Consuming a meal evokes a suite of physiological changes in pythons including one of the largest documented increases in post-feeding metabolic rates relative to resting values. However, little is known about how this plasticity manifests in the brain. Previous work has shown that cell proliferation in the python brain increases 6 days following meal consumption. This study aimed to confirm these findings and build on them in the long term by tracking the survival and maturation of these newly created cells across a 2-month period.

METHODS

We investigated differences in neural cell proliferation in ball pythons 6 days after a meal with immunofluorescence using the cell-birth marker 5-bromo-12'-deoxyuridine (BrdU). We investigated differences in neural cell maturation in ball pythons 2 months after a meal using double immunofluorescence for BrdU and a reptilian ortholog of the neuronal marker Fox3.

RESULTS

We did not find significantly greater rates of cell proliferation in snakes 6 days after feeding, but we did observe more new cells in neurogenic regions in fed snakes 2 months after the meal. Feeding was not associated with higher rates of neurogenesis, but snakes that received a meal had higher numbers of newly created nonneuronal cells than fasted controls. We documented particularly high cell survival rates in the olfactory bulbs and lateral cortex.

CONCLUSION

Consuming a meal stimulates cell proliferation in the brains of ball pythons after digestion is complete, although this effect emerged at a later time point in this study than expected. Higher rates of proliferation partially account for greater numbers of newly created non-neuronal cells in the brains of fed snakes 2 months after the meal, but our results also suggest that feeding may have a mild neuroprotective effect. We captured a slight trend toward higher cell survival rates in fed snakes, and survival rates were particularly high in brain regions associated with olfactory perception and processing. These findings shed light on the relationship between energy balance and the creation of new neural cells in the brains of ball pythons.

Postnatal and Adult Neurogenesis in Mammals, Including Marsupials

In mammals, neurogenesis occurs during both embryonic and postnatal development. In eutherians, most brain structures develop embryonically; conversely, in marsupials, a number of brain structures develop after birth. The exception is the generation of granule cells in the dentate gyrus, olfactory bulb, and cerebellum of eutherian species. The formation of these structures starts during embryogenesis and continues postnatally. In both eutherians and marsupials, neurogenesis continues in the subventricular zone of the lateral ventricle (SVZ) and the dentate gyrus of the hippocampal formation throughout life. The majority of proliferated cells from the SVZ migrate to the olfactory bulb, whereas, in the dentate gyrus, cells reside within this structure after division and differentiation into neurons. A key aim of this review is to evaluate advances in understanding developmental neurogenesis that occurs postnatally in both marsupials and eutherians, with a particular emphasis on the generation of granule cells during the formation of the olfactory bulb, dentate gyrus, and cerebellum. We debate the significance of immature neurons in the piriform cortex of young mammals. We also synthesize the knowledge of adult neurogenesis in the olfactory bulb and the dentate gyrus of marsupials by considering whether adult-born neurons are essential for the functioning of a given area.

In Vivo Electroporation and Time-Lapse Imaging of the Rostral Migratory Stream in Developing Rodent Brain

Interneurons in the olfactory bulb are generated from neuronal precursor cells migrating from the anterior subventricular zone (SVZa) throughout the embryonic and postnatal life of mammals. This article describes basic methods for in vivo electroporation to label SVZa cells of both embryonic and postnatal rats. In addition, it describes three methods for tracing SVZa progenitors and following their migration pathway and differentiation, including immunohistochemistry, time-lapse live imaging in slice culture, and time-lapse imaging following transplantation in slice culture. These methods may be applied to all strains of rats and mice, including reporter mice. They may also be combined with methods such as BrdU labeling, tamoxifen injection, and electrophysiology, allowing one to observe proliferation or control gene expression at specific times and for specific neuronal functions. With time-lapse live imaging, details of labeled cells can be studied, including morphology, motility pattern, differentiation, and crosstalk between cells. © 2019 by John Wiley & Sons, Inc.