RESUMO
This study explores the multifaceted influence of litter size, maternal care, exercise, and aging on rats' neurobehavioral plasticity and dentate gyrus microglia dynamics. Body weight evolution revealed a progressive increase until maturity, followed by a decline during aging, with larger litters exhibiting lower weights initially. Notably, exercised rats from smaller litters displayed higher body weights during the mature and aged stages. The dentate gyrus volumes showed no significant differences among groups, except for aged sedentary rats from smaller litters, which exhibited a reduction. Maternal care varied significantly based on litter size, with large litter dams showing lower frequencies of caregiving behaviors. Behavioral assays highlighted the detrimental impact of a sedentary lifestyle and reduced maternal care/large litters on spatial memory, mitigated by exercise in aged rats from smaller litters. The microglial dynamics in the layers of dentate gyrus revealed age-related changes modulated by litter size and exercise. Exercise interventions mitigated microgliosis associated with aging, particularly in aged rats. These findings underscore the complex interplay between early-life experiences, exercise, microglial dynamics, and neurobehavioral outcomes during aging.
RESUMO
Aging-related neurophysiological alterations are a matter of growing concern in gerontology. Physical exercise has been therapeutically employed to ameliorate aging-associated deleterious neurological changes. The aging process, as well as the effects of treadmill exercise on brain excitability, can be influenced by nutritional demands during lactation. In this study we investigated whether physical exercise, lactation conditions, and aging interact and modulate brain electrophysiology as indexed by the excitability-related phenomenon known as cortical spreading depression (CSD). Wistar male rats were suckled in litters of 12 or 6 pups (constituting two groups named L12 and L6), with different lactation conditions. Each group was subdivided into exercised (treadmill) and sedentary. CSD was recorded immediately after the exercise period for young, adult, and aged groups (respectively 45-60, 120-130, and 600-700 days old). In L6 groups, the mean CSD velocity (in mm/min) ranged from 2.57±0.24 in aged rats to 3.67±0.13 in young rats, indicating an aging-related CSD deceleration. The L12 condition accelerated CSD (velocities ranging from 3.11±0.21 to 4.35±0.16 in aged and young rats, respectively) while treadmill exercise decelerated it in both L6 groups (range: 3.02±0.19 to 2.57±0.24) and L12 groups (3.32±0.16 to 3.11±0.21), with an observed interaction between factors in the aged group. Furthermore, aging led to a significant failure of CSD propagation. These results contribute to the understanding of underlying mechanisms by which exercise and aging influence brain electrophysiological functioning, previously associated with distinct lactation conditions during the period of brain development.
