Early life inflammatory-stress increases seizure susceptibility later in life. However, possible sex- and age-specific differences and the associated mechanisms are largely unknown. C57/BL6 mice were bred in house, and female and male pups were injected with lipopolysaccharide (LPS, 100 μg/kg i.p. ) or vehicle control (saline solution) at postnatal day 14 (p14). Seizure threshold was assessed in response to pentylenetetrazol (1% solution, i.v. ) in adolescence (∼p40) and adulthood (∼p60). We found that adult, but not adolescent mice treated with LPS displayed ∼34% lower seizure threshold compared with controls. Females and males showed similar increased seizure susceptibility, suggesting that altered brain excitability was age, but not sex-dependent. Whole-cell recordings revealed no differences in excitatory synaptic activity onto CA1 pyramidal neurons from control or neonatally-inflamed adolescent mice of either sex. However, adult mice of both sexes previously exposed to LPS displayed spontaneous EPSC f...