Lack of changes in seizure susceptibility during the estrous cycle in kindled rats

The threshold and pattern of focal and generalized seizures in fully kindled rats during the estrous cycle were investigated. Two groups of rats were studied; one was kindled from stimulation of the basolateral amygdala, the other from stimulation of the anterior portion of the posterior piriform cortex. Determinations of the threshold for focal afterdischarges were either carried out in the morning (between 8 and 9 a.m.) or in the afternoon (between 2 and 3 p.m.). In all experiments, stable and reproducible afterdischarge thresholds were obtained during the different stages of the estrous cycle. The only significant alteration was a reduced seizure duration during metestrus and/or the first day of diestrus in amygdala kindled rats. The data indicate that the natural changes in sex hormone levels during the estrous cycle in rats do not affect seizure susceptibility, at least in the kindling model of epilepsy.