Experiencing early-life stress has been considered as a potent risk factor for the development of many of brain
disorders, including seizures. Intervening mechanisms through which neonatal maternal separation (MS) alters
the seizure susceptibility in adulthood have not been well studied. In the current study, by applying 180 min of
MS stress (PND 2–14), we determined the seizure susceptibility and considered the role of the opioid system.
Maternal separation increased the seizure threshold, and administration of anticonvulsant/proconvulsant
doses of morphine (1 and 30 mg/kg, respectively) reversed the impact of MS. Using tail flick and hot plate
tests, we exposed animals to 30 min Restraint stress (RS) and found that MS decreased the pain threshold,
suggesting the hyporesponsiveness of the opioid system. These results supported the abnormal seizure activity
observed in the MS mice and suggested that abnormalities in the opioid system following MS alter seizure
susceptibility in later life
