We hypothesized that neonatal seizures lead to increased Ca²⁺ influx (nCa²⁺I) in neuronal nuclei of newborn rats and that such increase is nitric-oxide mediated. Neuronal nuclear ⁴⁵Ca²⁺ influx (nCa²⁺I) was measured in neuronal nuclei of 25 10-day-old male rat-pups newborn brains. They were divided into five groups (n = 5/group). (I) control; (II) hypoxia without seizures; (III) hypoxia with seizures; (IV) kainate, 2 mg/kg intraperitoneal (i.p.)-induced seizures and (V) 7-nitroindazole (7-NINA), 1 mg/kg i.p. pretreated, kainate-induced seizures. nCa²⁺I was significantly (P < 0.05) increased following hypoxia or seizures (hypoxic- or kainate-induced). Post-hypoxic seizures further enhanced nCa²⁺I increase induced by hypoxia (P < 0.05). 7-NINA abated the nCa²⁺I increase induced by kainate. We conclude that (1) kainate or hypoxia-induced seizures in newborn rats modify the neuronal nuclear membrane function, resulting in increased nCa²⁺I, (2) seizures exacerbate the hypoxia-induced increased nCa²⁺I incurred after hypoxia and (3) intranuclear calcium surges during kainate-induced neonatal seizures are nitric oxide-mediated.