Aging is associated with cognitive decline, including impairments in the ability to accurately form and recall memories. Some behavioral and brain changes associated with aging are evident as early as middle age, making the understanding of associated neurobiological mechanisms essential to aid in efforts aimed at slowing cognitive decline throughout the lifespan. Here, we found that both 15-month-old and 22-month-old rats showed impaired memory recall following trace fear conditioning. This behavioral deficit was accompanied by increased zif268 protein accumulation relative to 3-month-old animals in the medial prefrontal cortex, the dorsal and ventral hippocampi, the anterior and posterior retrosplenial cortices, the lateral amygdala, and the ventrolateral periaqueductal gray. Elevated zif268 protein levels corresponded with decreases in phosphorylation of the Rpt6 proteasome regulatory subunit, which is indicative of decreased engagement of activity-driven protein degradation. Together, these results identify several brain regions differentially impacted by aging and suggest that the accumulation of proteins associated with memory retrieval, through reduced proteolytic activity, is associated with age-related impairments in memory retention.
Keywords: aging; immediate early gene; memory; proteasome; protein degradation.