Post-activation potentiation and the kindling phenomenon.

Potentials evoked in the hippocampus and preoptic region of rats by single biphasic pulses applied to the amygdala were compared during recruiting, after post-tetanic potentiation (PTP) and after amygdaloid kindling. The same components were enhanced temporarily by recruiting and PTP as were enhanced permanently by kindling. Trains of tetanic stimulation with parameters which partially mimicked the cellular discharge parameters during an amygdaloid afterdischarge (AD) were applied to the amygdala at a frequency of 1 per 5 sec continuously for 2.5 h or for 15 min a day for 10 days to produce a total of 1800 trains. Amygdaloid kindling rates were then measured and compared with control groups. Animals pretreated with tetanic stimulation required significantly fewer ADs to develop maximal seizures. Further experiments showed that tetanic stimulation, but not recruiting stimulation (10 c/sec), low frequency stimulation (1 c/sec), or handling, would produce a permanent change in potentials evoked in secondary sites by single pulses applied to the amygdala. This change in evoked potential amplitude was significant but smaller than that produced by kindling. Also tetanic stimulation, but not recruiting or single pulses, facilitated subsequent kindling.