Minute-Resolution Sampling Reveals Rapid and Stimulus-Specific IL-1β Dynamics During Acute Epileptiform Activity

Brain inflammation is increasingly recognized as a critical contributor to seizure generation and neuronal hyperexcitability. Among proinflammatory mediators, interleukin-1β (IL-1β) has been implicated in epileptogenesis; however, its acute temporal dynamics during seizure initiation remain poorly characterized because of limitations in conventional sampling approaches. In this study, we investigated the minute-by-minute intracerebral dynamics of IL-1β in a rat model of acute epileptiform activity induced by 4-aminopyridine (4-AP) and compared it with that induced by a classical inflammatory stimulus, lipopolysaccharide (LPS). Adult male Wistar rats (10-12 weeks old) were implanted with a push-pull guide cannula in the right lateral ventricle and electrodes over the ipsilateral and contralateral cortices to enable simultaneous cerebrospinal fluid (CSF) sampling and electroencephalographic (EEG) recordings. IL-1β concentrations were quantified at one-minute resolution using a nanodot blot immunodetection method, while epileptiform activity was assessed through EEG amplitude analysis and discharge train identification. Intraventricular administration of 4-AP (75 mM) induced robust epileptiform activity accompanied by a rapid and transient surge in IL-1β levels, reaching a peak concentration of 199 ± 28 ng/mL within 14 min (p < 0.05 vs. NaCl) and closely coinciding with the onset of epileptiform discharges. In contrast, intraventricular administration of LPS (25 µg/µL) elicited a delayed and sustained increase in IL-1β which was statistically significant at 240 and 300 min post-administration and did not induce epileptiform activity during the evaluated period. Although cumulative IL-1β exposure was comparable between 4-AP and LPS groups, their temporal profiles were markedly distinct. These findings demonstrate that acute epileptiform activity is associated with a rapid release of IL-1β that temporally coincides with seizure-like events, supporting a role for early cytokine signaling in seizure initiation. Moreover, this study highlights the importance of minute-resolution approaches for identifying neuroinflammatory processes that are otherwise obscured by conventional sampling strategies.