SBNeC 2010
Resumo:F.010


Prêmio
F.010Mild prenatal exposure to ethanol did not affect impulsivity in Wistar rats performing a delay discounting task
Autores:Stéfano Pupe (UFRGS - Inst. de Psicologia - Univ. Federal do Rio Grande do Sul) ; Ivani Brys (UFRGS - Inst. de Psicologia - Univ. Federal do Rio Grande do Sul) ; Philip Asherson (IOP/KCL - Institute of Psychiatry - King's College/London) ; Ian Stolerman (IOP/KCL - Institute of Psychiatry - King's College/London) ; Lisiane Bizarro (UFRGS - Inst. de Psicologia - Univ. Federal do Rio Grande do Sul)

Resumo

Introduction: Ethanol is a known teratogen, causing mental retardation and more subtle cognitive impairments. So far, few studies with animals attempted to investigate the effects of prenatal exposure to ethanol (PEE) on decision making and impulsivity. Thus the objective of this study was to investigate the possible link between the damage caused by a low dose of PEE on impulsive choice in a delay discounting task. Method: 21 male Wistar rats were used in this experiment. These rats were the offspring of 60 dams exposed to one of three conditions throughout pregnancy: a liquid diet containing either 10% ethanol-derived calories (EDC) or 0% EDC (control); or fed with ad libitum laboratory chow and water. Dams in all three groups were weight-matched, and the liquid diet groups were organized in triplets to ensure the ethanol and caloric intake of each group was similar. At two months of age, the rats were gradually restricted to 85% of their free-feeding weight. They were trained in automated 5-choice serial reaction time task operant boxes, which are equipped with five holes on one side and a wider hole in the other side, this one connected to a pellet dispenser. Every orifice is equipped with sensors to detect nose-pokes, and small lamps controlled by a computer. During training, a fixed ratio schedule was used, in daily 30-minutes sessions. Rats progressively learned to nose-poke the feeder orifice, after which one of two lights lit up on the other side, at the right-most or the left-most orifice. After nose-poking in it, a single pellet was dispensed at the feeder orifice. When rats achieved a stable performance, they were tested on the delay discounting task. The task consists of associating one orifice with a smaller, immediate reward (1 pellet) and another orifice with a bigger, delayed reward (4 pellets). The delay in this latter option progressively increased during the five blocks of the task (0s, 10s, 20s, 40s and 60s), each of which consisted of two forced choice trials and ten free choice trials. In the forced choice trials, each orifice (immediate and delayed) was presented once, individually. During free choice trials, both orifices lit up simultaneously. Only data from free choice trials during the baseline was analyzed. The criterion for achieving a baseline was the analysis of the last 3 sessions for each rat by a two-way ANOVA, with delay and day as factors. In this, rats had to show both a significant effect of delay (p<0.01), and a non-significant effect of day (p>0.05) to be considered for further analysis. Results: An analysis of variance showed that there was a significant effect of delay on preference (p<0,5), with rats consistently choosing the larger reward in the first block (>90% of choices in all groups) and progressively choosing the smaller, immediate reward as the delay increased. No significant difference was found between the three groups in the number of choices of delayed options at each block [F(17,2)=1.5, p=0.24]. The same was true for the number of omissions [F(17,2)=2.5, p=0.10] and latency to initiate trials [F(17,2)=1.0, p=0.64]. These results suggest that ethanol in this dose did not impact impulsivity associated with temporal discounting in this task. Further studies are necessary to investigate if higher dosages might cause a detectable effect, or if a moderate PEE produces other types of cognitive abnormalities. This study was supported by the Wellcome Trust and CNPq.


Palavras-chave:  Delay Discounting, Prenatal Exposure to Ethanol, Impulsivity