The effect of interstimulation interval on the assessment and stability of kindled seizure thresholds

Two experiments were conducted to investigate the importance of the interstimulus interval (ISI) in the assessment of kindled seizure thresholds using an ascending method of limits. A third experiment examined the effect of varying the interval between successive threshold tests on threshold stability. No differences in afterdischarge (AD) or motor seizure (MS) threshold were observed when the ISI was either five minutes or 48 hours. However, a 30 second ISI yielded significantly higher AD and MS thresholds and shorter seizure duration compared to 1, 3, or 5 minute ISI's. AD and MS thresholds were found to be relatively stable over five successive tests when the inter-test interval was 48 hours. An inter-test interval of 24 hours, however, yielded progressively higher thresholds over the five tests.