Impaired olfactory neurogenesis affects the performance of olfactory-guided behavior in aged female opossums

Beata Tepper,Paulina Koguc-Sobolewska,Katarzyna Bartkowska,Krzysztof Turlejski,Ruzanna Djavadian,Katarzyna Jaslan

doi:10.1038/s41598-021-83834-5

Abstract

Increasing evidence has indicated that adult neurogenesis contributes to brain plasticity, although function of new neurons is still under debate. In opossums, we performed an olfactory-guided behavior task and examined the association between olfactory discrimination-guided behavior and adult neurogenesis in the olfactory bulb (OB). We found that young and aged opossums of either sex learned to find food buried in litter using olfactory cues. However, aged females required more time to find food compared to aged males and young opossums of both sexes. The levels of doublecortin, that is used as a marker for immature neurons, were the lowest in the OB of aged female opossums. Another protein, HuD that is associated with learning and memory, was detected in all layers of the OB, except the granule cell layer, where a high density of DCX cells was detected. The level of HuD was higher in aged opossums compared to young opossums. This indicates that HuD is involved in plasticity and negatively regulates olfactory perception. The majority of 2-year-old female opossums are in the post-reproductive age but males of this age are still sexually active. We suggest that in aged female opossums neural plasticity induced by adult neurogenesis decreases due to their hormonal decline.

Highlights

Increasing evidence has indicated that adult neurogenesis contributes to brain plasticity, function of new neurons is still under debate
They are constantly replaced with newly generated neurons that are generated in the subventricular zone of the lateral ventricle (SVZ) and migrate through the rostral migratory stream (RMS) to the O B3
Research on marsupial species provides evidence that adult neurogenesis continues in the SVZ and dentate gyrus throughout life and the rate of neurogenesis declines with age[7]

Summary

Introduction

Increasing evidence has indicated that adult neurogenesis contributes to brain plasticity, function of new neurons is still under debate. The levels of doublecortin, that is used as a marker for immature neurons, were the lowest in the OB of aged female opossums. Another protein, HuD that is associated with learning and memory, was detected in all layers of the OB, except the granule cell layer, where a high density of DCX cells was detected. We suggest that in aged female opossums neural plasticity induced by adult neurogenesis decreases due to their hormonal decline. Our recent findings have shown that there is a correlation between individual differences in the level of doublecortin (DCX), that is a marker for immature neurons, and performance in the Morris water maze test[9]. Changes in HuD expression are associated with hippocampal spatial learning and memory processes[14,15]

Methods

Results

Conclusion