Diversity of kindling of limbic seizures after lateral fluid percussion injury in the rat

Lateral fluid percussion injury (LFPI) in rats is used to model post‐traumatic epilepsy (PTE), with spontaneous seizures occurring in up to ½ of the subjects. Using the kindling paradigm, we examined whether animals without detectable seizures had an altered seizure susceptibility. Male Sprague Dawley rats were subjected to LFPI. Seven‐nine months later, spontaneous seizures were monitored for two weeks. Afterward, the animals underwent kindling of basolateral amygdala. For kindling outcomes, the animals were categorized based on the 95% confidence intervals of mean number trials to kindling (ie 3 consecutive stage 4‐5 seizures). Spontaneous seizures were detected in 7 out of 24 rats. There was no correlation between the severity of LFPI and either baseline afterdischarge properties, or kindling rates. Six LFPI rats kindled at a rate comparable to those in sham‐LFPI (n = 10) and in naïve (n = 7) subjects. Ten LFPI rats kindled faster and 8—slower than controls. None of slow‐kindling rats had spontaneous seizures during the prekindling monitoring. During the same period, six fast‐kindling and three normal‐kindling rats had been seizure‐free. Thus, kindling reveals a diversity to seizure susceptibility after LFPI beyond an overt seizure symptomatology, ranging from the increased susceptibility to the increased resistance.