Abstract
The severity of sensory involution during aging is critical for perceiving and recognizing the world. In addition, sensory deficits significantly increase the risk of older adults’ biological, mental, and social decline. Conversely, the loss of smell is an early biomarker of neurodegeneration in Alzheimer’s (AD) and Parkinson’s diseases. The worsening of these neurodegenerative diseases also involves physical deterioration, social deficits, and isolation. In the present translational work, a new food finding test (FFT) olfactory paradigm without food deprivation was used to investigate olfaction in old animals. The effects of social isolation in 12-months-old female 3xTg-AD mice, a genetic model of AD, and their age-matched wild-type counterparts, the gold-standard C57BL/6 mice, were also studied. The animals were placed in a test cage and were observed until reaching the criteria for three goal-directed behaviors, ‘Sniffing’, ‘Finding’ and ‘Eating’, towards the hidden food. Video recordings were analyzed blind to the genotype and social condition in order to determine the behaviors’ ethogram and functional correlations. The results showed that the FFT paradigm without food deprivation elicited longer ethograms than previously reported with the standard overnight food deprivation protocol. However, it identified the genotype-dependent olfactory signatures in normal and AD-pathological aging. Social isolation slightly increased the latencies, but the olfactory signatures were preserved. However, a functional derangement was detected since the internal correlation among the three goal-directed behaviors was lost under isolation. In conclusion, the new paradigm without overnight deprivation was sensitive to genotype and isolation changes in the ethogram and function and can be used to study old animals.
Supplementary Materials
The presentation material of this work is available online at https://www.mdpi.com/article/10.3390/IECBS2022-13741/s1.
Author Contributions
D.M.-P. and L.G.-L., conceptualization; D.M.-P., behavioral performance, data analysis and writing; L.G.-L. supervision and editing. Both authors revised and approved the final manuscript. All authors have read and agreed to the published version of the manuscript.
Funding
The colonies were sustained by Fet-Open ArrestAD European Union’s Horizon 2020 research and innovation program under grant agreement No. 737390 to L.G.-L.
Institutional Review Board Statement
The study was conducted according to the guidelines of the Declaration of Helsinki and approved by the Ethics Committee of Departament de Medi Ambient I Habitatge, Generalitat de Catalunya (CEEAH 3588/DMAH 9452) the 8 March 2019.
Informed Consent Statement
Not applicable.
Data Availability Statement
Data are not publicly available due to ongoing analyses for future publications.
Conflicts of Interest
The authors declare no conflict of interest.
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