Effect of drugs which inhibit tryptophan hydroxylase or dopamine-β-hydroxylase on pinealectomy-induced seizures in parathyroidectomized rats

1. 1. If 21 day-old male rats are parathyroidectomized (PTX) and a week later are pinealectomized (PX) about 80 per cent of the animals exhibit repeated seizures during the first 8 hr following PX. Within 48 hr roughly 35 per cent of these animals die. 2. 2. The administration of FLA-63, a dopamine-β-hydroxylase inhibitor, 60 min after PX caused a rapid onset of the seizures in all the animals. Additionally, 100 per cent of the rats given FLA-63 were dead within 3 hr of PX. 3. 3. The injection of p-CPA, a tryptophan hydroxylase inhibitor, at 48 and 24 hr preceding PX, only slightly increased the frequency of the seizures. 4. 4. The administration of a melatonin-free pineal extract had no influence on the convulsive episodes in PTX + PX rats. 5. 5. In support of previously obtained biochemical data, the results suggested that depressed brain norepinephrine may somehow be related to the seizures in PTX + PX rats.