Effects of embryonic exposure to polychlorinated biphenyls (PCBs) on larval zebrafish behavior

Abstract

Developmental disorders such as anxiety, autism, and attention deficit hyperactivity disorders have been linked to exposure to polychlorinated biphenyls (PCBs), a ubiquitous anthropogenic pollutant. The zebrafish is widely recognized as an excellent model system for assessing the effects of toxicant exposure on behavior and neurodevelopment. In the present study, we examined the effect of sub-chronic embryonic exposure to the PCB mixture, Aroclor (A) 1254 on anxiety-related behaviors in zebrafish larvae at 7 days post-fertilization (dpf). We found that exposure to low concentrations of A1254, from 2 to 26 hours post-fertilization (hpf) induced specific behavioral defects in two assays. In one assay with intermittent presentations of a moving visual stimulus, 5 ppm and 10 ppm PCB-exposed larvae displayed decreased avoidance behavior but no significant differences in thigmotaxis or freezing relative to controls. In the other assay with intermittent presentations of a moving visual stimulus and a stationary visual stimulus, 5 ppm and 10 ppm PCB-exposed larvae had elevated baseline levels of thigmotaxis but no significant differences in avoidance behavior relative to controls. The 5 ppm larvae also displayed higher terminal levels of freezing relative to controls. Collectively, our results show that exposure to ecologically valid PCB concentrations during embryonic development can induce functional deficits and alter behavioral responses to a visual threat.

Effects of embryonic exposure to polychlorinated biphenyls (PCBs) on anxiety-related behaviors in larval zebrafish

“…Our novel finding of potentiated thigmotaxis in PCB-treated larvae in an extended free swimming period (phase 1) is in line with these reports of an anxiogenic effect of PCB-exposure and partially aligns with results of Lovato et al (2016). However, our VSA data do little to strengthen an anxiogenic account of PCB-exposure effects.…”

“…Details of our breeding population of adult male and female wild type zebrafish, their housing and maintenance schedule, and our protocol for embryo collection were the same as those described in Lovato et al (2016). Briefly, mixed sex adults were housed in 20 gallon tanks and maintained on a 14 h light/10 h dark cycle.…”

“…Details of our PCB exposure and embryo rearing protocols were identical to those described in Lovato et al (2016). Briefly, individual stock solutions of 2, 5 and 10 mg/ml of Aroclor (A) 1254 (Ultra Scientific, Kingston, RI) in dimethyl sulfoxide (DMSO) were diluted (matching the 0.1% DMSO control) to final concentrations of 2, 5, and 10 ppm in egg water (60mg/l Instant Ocean in deionized water and 0.25 mg/l methylene blue).…”

“…3506) have been described previously (Pelkowski et al, 2011; Lovato et al, 2016). Four 6-well plates with one larva per well were placed on the LCD screen (1366 × 768 pixel resolution and a brightness of 220 cd/m 2 ) of an inverted laptop on the bottom shelf of a tall cabinet.…”

“…Recently, our laboratory reported that exposure to 5 ppm and 10 ppm of A1254 during early-stage embryonic development (2 to 26 hours post-fertilization, hpf) altered anxiety-related behaviors in 7 dpf zebrafish larvae on a visual avoidance assay (Lovato et al, 2016). Briefly, in one experiment, the PCB-exposed larvae were less likely than the control larvae to avoid a red ‘bouncing’ disk, a stimulus that is perceived as a visual threat (Pelkowski et al, 2011), that was presented intermittently for two hours.…”