Associations of concurrent PCB and PBDE serum concentrations with executive functioning in adolescents.

Polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) are ubiquitous environmental chemicals that have long half-lives. Humans are exposed to PCBs and PBDEs mainly through diet, and relative to other populations, those who consume sport-caught fish generally have elevated body burdens. Numerous studies have found associations between prenatal exposure to these chemicals and neurodevelopmental deficits, but there are few studies assessing the impact of exposure during adolescence, a period of rapid development of executive functions. We assessed executive functions in adolescents at risk for exposure to PCBs and PBDEs through consumption of fish from the Lower Fox River and other contaminated waters in northeastern Wisconsin. Between 2007 and 2012, a sample of 115 12-18-year-old children was recruited from households in the Green Bay, WI area in which at least one parent held a WI fishing license. We assessed associations of total PCBs and total PBDEs, as well as the predominant individual congeners (PBDE 47 and 153; PCB 138/163, 153 and 180) with performance on four tests from the Cambridge Neuropsychological Test Automated Battery (CANTAB): Intradimensional/Extradimensional Set-Shifting (ID/ED) which assesses cognitive flexibility, Delayed Matching to Sample (DMS) which assesses visual recognition memory, Spatial Working Memory (SWM), and Stockings of Cambridge (SOC) which assess planning and working memory. In addition to the exposure and outcome variables, multivariable regression models included the child's age, sex and IQ score as well as a sex by exposure interaction term. All of the children were non-Hispanic whites and most parents were married, employed, and had at least some college. After adjusting for serum lipids, the GM (GSD) for total PCBs (ng/g) was 30.83 (2.46), and the GM (GSD) for the predominant PCB congeners PCB 138/163, PCB 153, and PCB 180 were 4.60 (2.39), 5.43 (2.37), and 1.01 (2.71), respectively. The GM (GSD) for total PBDEs (ng/g) was 26.82 (3.30), and the GM (GSD) for the predominant PBDE congeners PBDE 47 and PBDE 153 were 16.64 (2.94) and 3.95 (3.43), respectively. For both chemicals, the primary finding of the negative binomial regression analyses was that higher blood serum concentrations were associated with poorer cognitive flexibility as measured on the ID/ED task. In particular, the PCB x sex interaction p-value was 0.08, and stratifying by sex demonstrated that males with higher blood serum total PCB concentrations (ß = 2.20, 95% CL: 1.16, 4.16, p = 0.02) took more trials to complete the ID/ED task, while both males and females with higher total PBDE concentrations (ß = 1.74, 95% CL: 1.25, 2.42, p = 0.001) took more total trials to complete the task. Higher serum total PCB concentrations were also associated with more errors on the DMS task (ß = 1.15, 95% CL: 1.00, 1.31, p < 0.05). These findings suggest that exposure to PCBs or PBDEs during adolescence may be associated with impaired cognitive flexibility and that adolescent PCB exposure may be associated with visual recognition memory deficits.

Extraction and Dissection of the Domesticated Pig Brain.

Use of the pig as a preclinical and translatable animal model has been well-documented and accepted by research fields investigating cardiovascular systems, gastrointestinal systems, and nutrition, and the pig is increasingly being used as a large animal model in neuroscience. Furthermore, the pig is an accepted model to study neurodevelopment as it displays brain growth and development patterns similar to what occurs in humans. As a less common animal model in neuroscience, surgical and dissection procedures on pigs may not be as familiar or well-practiced among researchers. Therefore, a standardized visual protocol detailing consistent extraction and dissection methods may prove valuable for researchers working with the pig. The following video showcases a technique to remove the pig brain while keeping the cortex and brainstem intact and reviews methods to dissect several commonly investigated brain regions including the brainstem, cerebellum, midbrain, hippocampus, striatum, thalamus, and medial prefrontal cortex. The purpose of this video is to provide researchers with the tools and knowledge necessary to consistently perform a brain extraction and dissection on the four-week-old pig.

Dietary polydextrose and galactooligosaccharide increase exploratory behavior, improve recognition memory, and alter neurochemistry in the young pig.

OBJECTIVES: Previous studies have shown that dietary prebiotics have the potential to improve memory, alter social behavior, and reduce anxiety-like behaviors in rodents. The present research sought to expand upon such results and describe the effects of feeding prebiotics early in life on cognition and neurochemistry using a translational piglet model. METHODS: Pigs were provided customized milk replacer containing 2 g/L each of polydextrose (PDX) and galactooligosaccharide (PDX/GOS) or 0 g/L (Control) from postnatal day (PND) 2-33. Beginning on PND 25, pigs were tested on the novel object recognition (NOR), novel location recognition (NLR), and backtest tasks to measure recognition memory and response to restraint stress. At study conclusion pigs were euthanized and intestine, blood, and brain tissues were collected and analyzed. RESULTS: PDX/GOS-fed pigs demonstrated recognition memory on the NOR task (P < 0.001) whereas Control pigs did not (P = 0.184). Additionally, PDX/GOS-fed pigs visited the novel and sample objects more frequently (all P < 0.05) while spending less time per visit exploring the sample object (P = 0.028) than Control pigs. Volatile fatty acids (VFAs) were decreased in the ascending colon (P < 0.012), whereas butyrate tended to be higher in blood (P = 0.080) and lower in the hippocampus (P = 0.061) of PDX/GOS-fed pigs. PDX/GOS-fed pigs exhibited lower serotonin (P = 0.016) in the hippocampus. CONCLUSION: These findings suggest that early life consumption of PDX/GOS supports recognition memory as measured by NOR while modulating the concentrations of VFAs in the colon, blood, and brain, as well as hippocampal serotonin.

Licorice root components mimic estrogens in an object location task but not an object recognition task.

This study investigated the efficacy of components of licorice root to alter performance on two different recognition tasks, a hippocampus-sensitive metric change in object location (MCOL) task and a striatum-sensitive double object recognition (DOR) task. Isoliquiritigenin (ISL), licorice root extract (LRE), and whole licorice root powder (LRP) were assessed. Young adult female rats were ovariectomized (OVX) and exposed to ISL, LRE or LRP at 0.075%, 0.5% or 5% respectively in the diet. An estradiol group was included as a positive control based on our prior findings. Rats were allowed to explore two objects for three 5-min study trials (separated by 3-min intervals) before a fourth 5-min test trial where the objects were moved closer together (MCOL task) or replaced with two new objects (DOR task). Rats typically habituate to the objects across the three study trials. An increase in object exploration time in the test trial suggests the rat detected the change. Estradiol improved MCOL performance and impaired DOR performance, similar to previously shown effects of estradiol and other estrogens, which tend to improve learning and memory on hippocampus-sensitive tasks and impair striatum-sensitive cognition. LRP had no effect on recognition while exposure to ISL and LRE improved MCOL performance. Exposure to ISL, LRE and LRP failed to attenuate DOR, contrary to effects of estradiol shown here and to previous reports in young-adult OVX rats. These findings suggest components of licorice root may prove to be effective therapies targeting memory enhancement without unintended deleterious cognitive effects.

The effects of the botanical estrogen, isoliquiritigenin on delayed spatial alternation.

Age-related declines in cognitive function can impair working memory, reduce speed of processing, and alter attentional resources. In particular, menopausal women may show an acceleration in the rate of cognitive decline as well as an increased vulnerability to brain diseases as estrogens may play a neuroprotective and neurotrophic role in the brain. To treat menopausal symptoms, many women turn to botanical estrogens that are promoted as a safe and natural alternative to traditional hormone replacement therapy. However, the majority of these compounds have not been systematically evaluated for efficacy and safety. The current study investigated the efficacy of the commercially available botanical estrogenic compound isoliquiritigenin (ISL) to alter performance on an operant working memory task, delayed spatial alternation (DSA). ISL is a compound found in licorice root that has been shown to have a wide range of effects on different biological systems, including estrogenic properties. This botanical is currently being used in over the counter dietary supplements. Middle-aged (12-month old) Long-Evans female rats were ovariectomized and orally dosed with either 0 mg, 6 mg, 12 mg or 24 mg of ISL 60 min before testing on the DSA task. The DSA task required the rat to alternate its responses between two retractable levers in order to earn food rewards. Random delays of 0, 3, 6, 9 or 18 s were imposed between opportunities to press. ISL treatment failed to alter DSA performance. Previous work from our research group has found that estrogenic compounds, including 17ß-estradiol and the botanical estrogen genistein impair performance on the DSA task. The goal of our botanical estrogens research is to find compounds that offer some of the beneficial effects of estrogen supplementation, without the harmful effects. This work suggests that ISL may not carry the cognitive risks associated with most other estrogenic compounds tested to date.

Strategy set-shifting and response inhibition in adult rats exposed to an environmental polychlorinated biphenyl mixture during adolescence.

Converging evidence from studies with animal models and humans suggests that early developmental exposure to polychlorinated biphenyls (PCBs) leads to deficits in cognitive flexibility and inhibitory control. These processes are mediated to a large extent by the prefrontal cortex, thus we examined the effects of PCB exposure during adolescence-a period of robust prefrontal cortical development-on both processes. Specifically, we used operant set-shifting and differential reinforcement of low rates of responding (DRL) tasks to assess cognitive flexibility and response inhibition, respectively. One male and one female pup from each of 14 litters were assigned to each of three treatment groups: 0, 3 or 6mgPCB/kg/day. Rats were dosed orally from postnatal day (PND) 27-50 to capture the whole period of adolescence in rats. At approximately PND 90, they began testing in the set-shifting task which included an initial visual cue discrimination, an extra-dimensional shift to a position discrimination and a reversal of the position discrimination. There were no statistically significant group differences in errors to criterion on visual cue discrimination or on the shift from visual to position discrimination in either males or females. During the position reversal, the 6mg/kg PCB males made significantly fewer errors to reach criterion than control males. The 3mg/kg PCB males showed a trend in the same direction, but this did not reach statistical significance. Interestingly, error analysis revealed that PCB-exposed males made significantly fewer perseverative errors than controls in this phase. No group differences were observed in females. These results suggest a male-specific effect of adolescent PCB-exposure on the reversal phase of the set-shifting task. Following set-shifting, rats progressed to the DRL task in which they were required to withhold responding for a specified period of time (15s) in order to receive a reinforcer. There were no exposure-related group differences in total presses or efficiency ratio in males or in females. In summary, there were subtle sex-specific effects of adolescent PCB exposure on the reversal phase of a set-shifting task, but no effects of exposure on performance on a DRL15 task, suggesting an effect on cognitive flexibility but not response inhibition.

Developmental exposure to polychlorinated biphenyls reduces amphetamine behavioral sensitization in Long-Evans rats.

PCBs have long been known to affect dopamine (DA) function in the brain. The current study used an amphetamine behavioral sensitization paradigm in rats developmentally exposed to PCBs. Long-Evans rats were given perinatal exposure to 0, 3, or 6mg/kg/day PCBs and behavioral sensitization to d-amphetamine (AMPH) was assessed in one adult male and female/litter. Non-exposed (control) males showed increasing locomotor activity to repeated injections of 0.5mg/kg AMPH, typical of behavioral sensitization. PCB-exposed males showed greater activation to the initial acute AMPH injection, but sensitization occurred later and was blunted relative to controls. Sensitization in control females took longer to develop than in the males, but no exposure-related differences were observed. Analysis of whole brain and serum AMPH content following a final IP injection of 0.5mg/kg revealed no differences among the exposure groups. Overall, these results indicated developmental PCB exposure can alter the motor-stimulating effects of repeated AMPH injections. Males developmentally exposed to PCBs appeared to be pre-sensitized to AMPH, but quickly showed behavioral tolerance to the same drug dose. Results also revealed the behavioral effect was not due to exposure-induced alterations in AMPH metabolism following PCB exposure.

Discriminative stimulus effects of cocaine and amphetamine in rats following developmental exposure to polychlorinated biphenyls (PCBs).

Polychlorinated biphenyls (PCBs) are environmental neurotoxicants known to affect the brain dopaminergic (DA) system. This project investigated whether developmental exposure to PCBs would alter the discriminative stimulus effects of psychostimulant drugs known to act on the DA system. Female Long-Evans rats were orally exposed to 0, 3, or 6 mg/kg/day of an environmentally relevant PCB mixture from four weeks prior to breeding through weaning of their litters on PND 21. When they reached adulthood one male and female/litter were trained to discriminate cocaine (10.0 mg/kg, IP) from saline by repeatedly pairing cocaine injections with reinforcement on one operant response lever, and saline injections with reinforcement on the other lever. After response training, generalization tests to four lower doses of cocaine (7.5, 5.0, 2.5, and 1.25 mg/kg, IP) and to amphetamine (1.0, 0.5, 0.25, and 0.125 mg/kg, IP) were given two days/week, with additional training dose days in-between. Percent responding of the PCB-exposed rats on the cocaine-paired lever was significantly higher than that of controls for the highest generalization dose of cocaine, and lower than that of controls for the highest dose of amphetamine. Response rate and percent responding on the cocaine lever did not differ among the exposure groups on the days when the training dose of cocaine was given, suggesting that the generalization test results were not due to pre-existing differences in discrimination ability or rate of responding. These findings suggest that developmental PCB exposure can alter the interoceptive cues of psychostimulants.