Effects of BPA on Memory
Bisphenol-A is a chemical that is found in food and beverage containers (Nienstedt, 2013). Many studies suggest that exposure to Bisphenol-A (BPA) during early development may cause memory inadequacy later in life. A study conducted by Luine, Eilam-Stock, Serrano & Frankfurt (2011), sought to investigate the effects of BPA on spatial and visual memory in adult rats. In their paper, they describe the influence of BPA on the brain areas that affect memory such as the hippocampus and prefrontal cortex. It is shown that estrogen and androgens play an important role in memory. But, BPA tends to inhibit estrogen increase in spine synapse formation as well as block androgens in spine synapses in the hippocampus and prefrontal cortex.
This study was conducted to not only see the effects of spatial and visual memory, but also if the effects are linked to CA1 area of the hippocampus and the medial prefrontal cortex (mPFC, since those specific areas of the brain are responsible for the memory function. The hypothesis for this study is that acute BPA exposure would harm memory in adult rats, decrease spine density in the hippocampus and mPFC, as well as inhibit the activity of memory association related proteins in those areas.
The species that were involved were Male Sprague- Dawley rats, aged 60 days upon their arrival. Animals were kept in a 12 hour light-dark cycle, with two rats in each cage with access to unlimited food and water. Their memory abilities were evaluated using object recognition (OR) and object placement (OP) tasks. Both trials began with a sample trail (T1) where rats were in an open box with two similar objects and were allowed to explore them for 3 minutes. After an intertrial interval, the rat is returned to the box for 3 minutes (T2). In the OR task, one of the objects is replaced by a different object in T2. In the OP task, one of the objects is placed in a different location in T2. In both tasks, if the rat remembers the old object/placement, it will spend more time with the new one. But if the rat does not remember it, it will spend the same amount of time on both objects. On the 1st day of the test, after the rat completes T1, it is immediately injected with 4ug//kg of BPA. Two hours after, they do the T2.
Procedure: Two experiments were performed. The first consisted of giving the rats a week of getting used to the housing environment, followed by two weeks of habituation to the OR and OP tasks as well as BPA injections. Four days after the OR test, the rats did the OP test. Eleven days after the last task, the rats did the T1 test again followed by an injection of BPA. The rats were immediately killed 40 minutes after the BPA injection. The brains were removed and assessed. In the second experiment, it consisted of the examining the effects of BPA by itself on the dendritic spine density. There was no OR or OP test given. The rats were killed 4 hours after the injection and the brains were removed for assessment.
I believed that sufficient controls were in place because for the 1st task, groups were switched in between so that the rats that did the OR test got BPA in the OP test and vice versa. Also the toys were replaced or switch in different positions to see if the rat would remember it.