Effect of ketamine on dentate gyrus of hypothyroid rats throughout lidocaine kindling

Previous studies in our laboratory have shown that a decrement in serum thyroid hormones in rats increases seizure susceptibility to lidocaine-kindled seizures. As GABA administration into the hippocampal dentate gyrus region (DG) of hypothyroid rats does not protect against lidocaine-kindling seizures, we tested if the administration of ketamine, a selective NMDA receptor antagonist, could prevent lidocaine-kindling. Male Wistar rats (280-430 g) were used. They received 60 mg/kg daily of methimazole for four weeks. A cannula guide was implanted in all the animals in DG (AP: -3mm; L: -1 ; DV: 3mm) for the administration of lui of ketamine (0.5 M) throughout lidocaine kindling protocol. Lidocaine was injected daily in doses of 60mg/g, ip. The results show that ketamine does not protect against lidocaine-kindling seizures. However, the severity of seizures is lower than in hypothyroid rats without ketamine. These results suggest the both types of glutamatergic receptors participate on the increment of susceptibility founded in hypothyroid rats.