1/13/2024 0 Comments Normal optical pathological agingAnalysis of the number of progenitors, proliferative and mature neurons revealed that naturally aged animals show reduced neuronal proliferation and decreased levels of sensory mature OMP + neurons. To gain insight into these questions, we investigated the impact of natural and pathological aging in social odor-evoked sniffing behavior, social-odor habituation/dishabituation, and sociability during the aging process of wild-type C57/BL6 mice and amyloid precursor protein (APP) and presenilin 1 (PS1) double transgenic mice (APP/PS1 Het mice, therein), a widely used animal model of AD. ![]() However, it is currently unclear whether these cell alterations have any impact in social odor detection, particularly in animal models of neurodegeneration. (2021) reported a significant reduction in mature olfactory marker protein (OMP)-expressing cells (OMP +), indicating structural modifications of the aged VNO. An elegant study by Brann and Firestein showed that the proliferative capacity of the marginal region of the VSE of 2-year-old animals was attenuated in comparison to young animals. However, how natural and pathological aging affects the regenerative capacity of the VSE has been scarcely studied despite being central to socio-sexual cue detection. The neurogenic properties of olfactory structures are known to decline with age, which it is likely to underlie the olfactory deficits associated to both natural aging and neurodegenerative disorders. Ī remarkable property of the VSE is that it contains proliferative niches capable of generating functional neurons during adulthood. Despite the segregated connectivity, both systems have overlapping functions. Volatile odors are primarily detected at the main olfactory epithelium (MOE) which projects to the main olfactory bulb (MOB), whereas pheromones are mainly detected by the vomeronasal sensory epithelium (VSE) which connects to the accessory olfactory bulb (AOB). Mouse social communication strongly depends on chemosignals comprised by volatile and non-volatile molecules (pheromones). Despite the central role of social interaction in maintaining overall well-being, the mechanisms by which aging, natural or pathological, alters social information processing remain unclear. In humans, social impoverishment has been identified as a major aggravating factor for decreased life expectancy and an indicator of the appearance of dementia and neurodegenerative disorders such as Alzheimer’s disease (AD). As aging progresses, social odors have been shown to elicit attenuated responses, a phenomenon interpreted as a natural consequence of age-related decline in sensory perception. Social recognition is essential for survival allowing to appropriately adapt behavior across a variety of contexts. This study reveals fundamental differences in the cellular processes by which natural and pathological aging disrupts the exploration of social information and social behavior. Furthermore, social novelty was diminished in 1-year-old APP/PS1 mice, indicating that alterations in the processing of social cues are accelerated during pathological aging. Our findings indicate that aging disrupts the processing of social olfactory cues decreasing social odor exploration, discrimination, and habituation in both wild-type senescent (2-year-old) mice and in 1-year-old double mutant model of Alzheimer’s disease (APP/PS1). These alterations may support age-related deficits in the recognition of social cues and the display of social behavior. ![]() Whereas cell proliferation remained majorly preserved in 1-year-old APP/PS1 mice, naturally aged animals exhibited significant deficiencies in the number of mature, proliferative, and progenitor cells. Analysis of the vomeronasal organ, the main gateway to pheromone-encoded information, indicated that natural and pathological aging distinctively affects the neurogenic ability of the vomeronasal sensory epithelium. Normal aging and many age-related disorders such as Alzheimer’s disease cause deficits in olfaction however, it is currently unknown how natural and pathological aging impacts the detection of social odors which might contribute to the impoverishment of social behavior at old age further worsening overall health.
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