Behavioral data file following treatment of laboratory rats with paracetamol

Based on several lines of evidence, numerous investigators have suggested that acetaminophen exposure during early development can induce neurological disorders. We had previously postulated that acetaminophen exposure early in life, if combined with antioxidants that prevent accumulation of NAPQI, the toxic metabolite of acetaminophen, might be innocuous. In this study, we administered acetaminophen at or below the currently recommended therapeutic dose to male laboratory rat pups aged 4-10 days. The antioxidants cysteine and mannitol were included to prevent accumulation of NAPQI. In addition, animals were exposed to a cassette of common stress factors: an inflammatory diet, psychological stress, antibiotics, and mock infections using killed bacteria. At age 37-49 days, observation during introduction to a novel conspecific revealed increased rearing behavior, an asocial activity, in animals treated with acetaminophen plus antioxidants, regardless of their exposure to oxidative stress factors (2-way ANOVA; P < 0.0001). This observation would suggest that the initial hypothesis is incorrect, and that oxidative stress mediators do not entirely eliminate the effects of acetaminophen on neurodevelopment. This study provides additional cause for caution when considering the use of acetaminophen in the pediatric population, and provides evidence that the effects of acetaminophen on neurodevelopment need to be considered both in the presence and in the absence of oxidative stress.

Methods
Social play behavior was assessed in rats between postnatal days 37 through 49 days in accordance with Veenema and colleagues (citations in manuscript). Briefly, all subjects and stimulus animals will be handled for 5 consecutive days prior to the beginning of behavior testing. All experimental subject animals were isolated for 24 hours prior to behavioral testing to potentiate their motivation to engage in social interactions. All testing took place during the last two hours of the light phase. Animals were placed together with an unfamiliar animal belonging to the same experimental group. Clean cages with bedding were used, and activity was video recorded for 10 min. All behavioral videos were subsequently scored by an observer blind to the treatment condition of each animal using Solomon coder software (version beta 19.08.02; https://solomon.andraspeter.com/).

Behavioral bins were as follows: exploration, play, investigation, chasing, rearing, auto grooming, and allogrooming. Play activity was further assigned to the following bins: nape attacks, boxing, pinning, and supine. Rearing was assessed for all animals (2 per cage), and all other behaviors were assessed for only one animal per cage. All videos had a total of 600.2 seconds of graded behavior.