Perinatal hypothyroidism increases the susceptibility to lidocaine-kindling in adult rats.

The present study was developed to ascertain whether or not susceptibility to lidocaine-kindling persists into adulthood in perinatal hypothyroid rats. Pregnant Wistar rats were randomly divided into two groups: the first one, a control group, that drank tap water; and a second one, a hypothyroid group, were treated with 0.02% propylthiouracil in their drinking water from the 14th gestational day to the 10th postpartum day. The pups of both groups were maintained with food and tap water ad libitum until the experiment was over. The pups of each group were divided to test the susceptibility to lidocaine-kindling at 30 and 100 days old, for this, lidocaine (50 mg/kg, i.p.) was administered daily. The seizures were usually present in the form of tonic attacks of fore and hind limbs, followed by intermittent clonic movements. An animal was considered kindled when it showed clonic movements for two consecutive days. We observed that the number of stimuli necessary to produce lidocaine-kindling seizures in hypothyroid rats was significantly lower than in the control group for both ages. Also, the percentage of kindled rats aged 30 days (73% and 89%) was greater than aged of 100 days (26% and 59%) in both control and hypothyroid groups, respectively. In conclusion, the perinatal hypothyroidism increases the susceptibility to lidocaine-kindling in adult rats.