Abstract:
Epigenetic factors influence the early neurodevelopment of an organism with longlasting
effects on brain function and behavior. But underlying mechanisms of these
factors interactions are not fully elucidated. Polychlorinated biphenyls (PCBs) are
ubiquitous anthropogenic pollutants, among them non–dioxin-like (NDL) PCBs are
linked to neuropsychological dysfunctions in children. Therefore, present study
aimed to investigate the effects of PCB-95, one of the widespread NDL PCB
congener on startle response of an organism using zebrafish (Danio rerio) larvae as
a model. Embryos at 2 cell stage with intact chorions were exposed to different
concentrations (0.75, 1, 3, 5 ppm) of PCB-95. Exposure time was 1 day with 7 day
incubation period. Each treatment was consisted of four replicates with two controls
(egg water and dimethyl sulfoxide). Habituation assay was conducted at day 7 by
exposing zebra fish larvae to a visual pattern presented beneath the well plate (a red
‘bouncing’ disk which runs in a straight line at the rate of 1.50 cm/s at the upper half
of the well plate). Images were captured every 6s for 30 minutes. Swimming behavior
around the well was quantified based on either the animal’s position or its turning
behavior. PCB levels within exposed larvae were analyzed using gas
chromatography/electron capture detection (GC/ECD). Data were analyzed using
PROC GLM in SAS software. Mortality rates increased with PCB exposure and in
survivors, morphological deformations increased with increasing PCB
concentrations. Enhanced thigmotaxis was observed in the treated group and
concentration-dependent pattern also observed for latency to reaction, maximum turn
velocity (Vmax), time to reach Vmax and escape time. Data of present study can be
coupled with molecular techniques to permit or accelerate the determination of the
mechanisms behind anxiogenic and attention-disrupting effects of PCB exposure
documented in children.
