The effects of eserine and atropine on the epileptiform activity of chronically isolated cortex

A gerbil model of cerebral ischemia suitable for drug evaluation

Cerebral ischemia was produced in the Mongolian gerbil by bilateral occlusion of the carotid arteries. Although the cerebral ischemia so produced was not total, a mortality rate of 100% was obtained if the occlusion was maintained for 60 min in gerbils weighing 45--55 gm. Few deaths were observed after 50 min of bilateral carotid arterial occlusion. Test drugs were administered, after the removal of the arterial clips, to groups of gerbils to determine the mortality rate associated with each drug. Isoproterenol 50 mg/kg, amphetamine 5.0 mg/kg, and methylprednisolone 35 mg/kg improved survival after cerebral ischemia. Atropine 1 mg/kg, thiosemicarbazide 4 mg/kg, aminooxyacetic acid 100 mg/kg, theophylline 100 mg/kg, and phenytoin 50 mg/kg were associated with a reduced survival after cerebral ischemia. The known tendency of the gerbil to exhibit spontaneous seizures and the frequency and severity of the observed post-ischemic seizures suggest that the lethality of prolonged cerebral ischemia may be, in part, related to seizures triggered by the cerebral ischemia.

Neostigmine activated epileptiform discharge in the amygdala: electrographic-behavioral correlations

This investigation was carried out to test the hypothesis that amygdaloid epileptiform activity is due to cholinergic hyperactivity. It was designed to study the underlying physiopathology of, and to act as an experimental model for, psychomotor epilepsy. Neostigmine was injected intracerebrally into the amygdala of the cebus monkey with chronically implanted "chemitrodes" fitted with EEG recording electrodes. The injections were made in the basal amygdaloid nucleus which normally shows very high acetylcholinesterase (AChE) enzymatic activity in histochemical preparations. Neostigmine injection resulted in very high amplitude spike activity in the amygdala only. Other brain areas, including the neighboring temporal cortex, did not show any marked EEG changes. In the first day or two, these EEG changes were associated with myoclonus localized in the ipsilateral muscles of facial expression and also associated with masticatory seizures. Subsequently the animal became aggressive and remained so several months after the injection of neostigmine. The EEG changes continued for approximately 6 weeks. Intramuscular injections of atropine diminished the amplitude of the epileptiform EEG discharges and modified slightly the animal's behavior.