Prenatal alcohol exposure delays acquisition and use of skilled reaching movements in juvenile rats

Abstract

Prenatal alcohol exposure (PAE) has been previously reported to result in behavioral and cognitive deficits that continue into adulthood. These deficits are often manifested by poor performance on higher-order cognitive motor tasks, difficulties in maintaining postural balance, slower reaction times, and deficits in fine motor performance. The central causes of these cognitive and motor deficits have been studied in human and animal models. Rats have been shown to be capable of performing skilled reaching and grasping movements with their forepaws that exhibit many components of skilled reaching also found in human and non-human primates. Whether PAE affects skilled reaching movements in rats is unknown. In the present study, we investigated the effect of PAE on skilled reaching and grasping behavior in rats. Pregnant Sprague–Dawley rats were intragastrically gavaged daily with alcohol at a dose of 6 g/kg body weight from gestation day one (G1) through G20 that yielded average blood alcohol levels between 265 and 343 mg/dL. Non-alcohol groups, pairfed ( n = 4) and chowfed ( n = 9), served as nutritionally-matched and normal controls, respectively to the alcohol treatment group ( n = 12). At 7 weeks of age, all rats were deprived of food for one day. The next day, rats were individually placed in test cages where food could only be accessed by reaching through a grid and grasping small food pellets (20 mg) on a tray. All rats were naive to the task. The major findings in this study are: a) PAE significantly increased the average number of minutes to make a successful skilled reach (Alc mean ± SEM = 97.3 ± 16.9 min vs. non-Alc 52.3 ± 9.6 min), b) once a successful skilled reach was learned, non-alcohol control rats were no better than Alc rats in using the skilled reach to acquire food, c) no significant differences between groups were observed in the amount of food consumption or changes in body weight during test sessions. These findings provide an important first step into the role that PAE plays for the learning of new skills and will lead to studies of central mechanisms underlying more complex skilled reaching behaviors.