Paracetamol (acetaminophen) administration during neonatal brain development affects cognitive function and alters its analgesic and anxiolytic response in adult male mice.

Paracetamol (acetaminophen) is one of the most commonly used drugs for the treatment of pain and fever in children, both at home and in the clinic, and is now also found in the environment. Paracetamol is known to act on the endocannabinoid system, involved in normal development of the brain. We examined if neonatal paracetamol exposure could affect the development of the brain, manifested as adult behavior and cognitive deficits, as well as changes in the response to paracetamol. Ten-day-old mice were administered a single dose of paracetamol (30 mg/kg body weight) or repeated doses of paracetamol (30 + 30 mg/kg body weight, 4h apart). Concentrations of paracetamol and brain-derived neurotrophic factor (BDNF) were measured in the neonatal brain, and behavioral testing was done when animals reached adulthood. This study shows that acute neonatal exposure to paracetamol (2 × 30 mg) results in altered locomotor activity on exposure to a novel home cage arena and a failure to acquire spatial learning in adulthood, without affecting thermal nociceptive responding or anxiety-related behavior. However, mice neonatally exposed to paracetamol (2 × 30 mg) fail to exhibit paracetamol-induced antinociceptive and anxiogenic-like behavior in adulthood. Behavioral alterations in adulthood may, in part, be due to paracetamol-induced changes in BDNF levels in key brain regions at a critical time during development. This indicates that exposure to and presence of paracetamol during a critical period of brain development can induce long-lasting effects on cognitive function and alter the adult response to paracetamol in mice.