Abstract
Exposure to environmental tobacco smoke (ETS) in the early postnatal period has been associated with several diseases; however, little is known about the brain effects of ETS exposure during this critical developmental period or the long-term consequences of this exposure. This study investigated the effects of the early postnatal ETS exposure on both reference and working memory, synaptic proteins and BDNF from late infancy to early adulthood (P3-P73). BALB/c mice were exposed to ETS generated from 3R4F reference research cigarettes (0.73 mg of nicotine/cigarette) from P3 to P14. Spatial reference and working memory were evaluated in the Morris water maze during infancy (P20-P29), adolescence (P37-P42) and adulthood (P67-P72). Synapsin, synaptophysin, PSD95 and brain-derived neurotrophic factor (BDNF) were assessed at P15, P35 and P65 by immunohistochemistry and immunoblotting. Mice that were exposed to ETS during the early postnatal period showed poorer performance in the spatial reference memory task. Specifically, the ETS-exposed mice exhibited a significantly reduced time and distance traveled in the target quadrant and in the platform location area than the controls at all ages evaluated. In the spatial working memory task, ETS disrupted the maintenance but not the acquisition of the critical spatial information in both infancy and adolescence. ETS also induced changes in synaptic components, including decreases in synapsin, synaptophysin, PSD95 and BDNF levels in the hippocampus. Exposure to ETS in the early postnatal period disrupts both spatial reference and working memory; these results may be related to changes in synaptogenesis in the hippocampus. Importantly, most of these effects were not reversed even after a long exposure-free period.
Highlights
Tobacco is the most frequently used licit drug among pregnant women around the world
The results show both poorer acquisition and performance by the environmental tobacco smoke (ETS) animals relative to controls and a greater susceptibility of females to ETS exposure compared to males, in infancy
To the best of our knowledge, this is the first study showing the effects of ETS exposure during the early postnatal period on infant mouse brain development and the consequences of these effects in adolescence and adulthood
Summary
Tobacco is the most frequently used licit drug among pregnant women around the world. In North America, the use of tobacco during pregnancy is approximately 18% [1], and in countries such as the Netherlands, Turkey, Morocco, Surinam, Cape Verde and Antilles, its use among pregnant women reaches 30% [2]. Most of these studies do not focus on processes that are considered to be critical at this period [7,8,9,10]. The maturation of excitatory synaptic transmission, which takes place around the second postnatal week, is required for the expression of cognitive processes, such as learning and memory, in adults [11]
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