The effects of pre‐natal nicotine exposure on anxiety‐like behavior and ethanol place preference in adolescent Zebrafish
Authors: Harenchar Rachel A. , Bell Rebecca A. , Anderson Shawn M. 
Published: June 2021

Maternal smoking during pregnancy has significantly decreased over the years; however, it is extremely important to understand how smoking can affect not only the mother, but the child as well. Incidences of both anxiety disorders and drug abuse increase in humans with prenatal exposure to nicotine. These studies tested the hypotheses that adolescent Zebrafish exposed to 5.6 or 18 μmol concentrations of nicotine during the larval stage would show increased anxiety‐like behavior and increased place preference for ethanol than age‐matched controls without larval nicotine exposure. Following larval nicotine exposure, Zebrafish were raised in standard aquatic housing tanks in groups of 20 to 40. Adolescent Zebrafish were removed from these tanks and assessed in the Novel Tank and Conditioned Place Preference tests in two separate cohorts. Testing for each cohort lasted one week. Between 46 and 53 fish were assessed per nicotine exposure dose. Levels of anxiety‐like behavior were measured using the Novel Tank Test. Reduced time spent in the top zone, fewer entries made into the top zone and increased latency to enter the top zone of a novel tank were interpreted to indicate increased anxiety‐like behavior in this task, while the effect of prior nicotine exposure on locomotor activity was determined using total distance swum. In the Novel Tank Test, significant interactions of cohort x nicotine were revealed for locomotor activity, top zone time and number of top zone entries (P's < 0.05). Interestingly, post‐hoc ANOVA analyses showed significant effects of embryonic nicotine exposure for fish used in Cohort 1, but not Cohort 2. Adolescent Zebrafish previously exposed to 5.6 μmol nicotine showed increased distance swum than both control Zebrafish (P < 0.05) and 18 μmol Zebrafish (P < 0.01). 18 μmol Zebrafish spent less time in the top zone than both control fish and 5.6 μmol Zebrafish (P's < 0.05) and made fewer entries into the top zone than 5.6 μmol Zebrafish (P < 0.01), suggesting that exposure to the highest dose of nicotine promoted increased anxiety‐like behavior during adolescence in this task. These Zebrafish were then tested the following week using a Conditioned Place Preference paradigm. On Day 1, initial preference for gray or dotted regions of a conditioning chamber was determined. On Days 2 and 3, fish were exposed to 0%, 1% or 1.5% ethanol in the previously non‐preferred region of the experimental chamber to condition the fish to the drug‐paired region. On Day 4, a final preference test determined if the preference for the previously drug‐paired region changed. Increases in preference for the drug‐paired region suggested that ethanol was rewarding for the fish during the conditioning days. Control (0 μmol) fish appeared to acquire place preference for ethanol, whereas subjects exposed to 5.6 μmol and 18 μmol nicotine did not. This may reflect impaired learning or it may reflect that experimental conditions were less than optimal. These data suggest that early exposure to the high dose of nicotine increased anxiety‐like behavior, but did not significantly affect preference for ethanol in adolescent Zebrafish. Future studies may include evaluation of adult subjects, expanding the nicotine dosage range and assessing the effects of early nicotine exposure on HPA axis activity.Support or Funding InformationA.J. Palumbo Student Research Grant, Individual SURF Award through ASPET, NSF1259904 ‐ Biology ScholarsThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.