Comparison of an electocorticogram during a pentylenetetrazole seizure between hypoand euthyroid rats

Our previous studies have shown that a decrement in serum thyroid hormones in rats prolongs convulsions induced by acute pentylenetetrazole (PTZ), without threshold modification, while hypothyroid rats developed PTZ-kindled seizures faster than euthyroid rats. To find if different susceptibility is manifested in the electrocorticogram (ECoG), an ECoG-Fourier Analysis of a seizure induced by PTZ was compared between hypo- and euthyroid rats. Male Wistar rats (250-300 g) were randomly assigned to one of two groups: control (CG) and hypothyroid (hyG). The hyG received 60 mg/kg daily of methimazole for four weeks. Cortical electrodes were implanted in frontal lobe to all the rats for ECoG recording. One week after surgery, PTZ was injected in a convulsant dose of 60 mg/kg, ip. The ECoGFourier Analysis presents an increment of the intensity of the bands 2-4, 4-6 and 8-12 Hz during seizures. The greatest difference between hypo- and euthyroid rats is at 8-12 Hz band, being greater and longer in hypothyroid with respect to euthyroid. This difference could be reflected to the different susceptibility to PTZ seizures founded between hypo- and euthyroid rats.