MECHANISM OF SEIZURES INDUCED BY DI-ISOPROPYL FLUOROPHOSPHATE (DFP)

Abstract

1. A simple method for electrical recording from the caudate nucleus and thalamus in the rabbit was described. 2. The control tracings from the limbic cortex, motor cortex, caudate nucleus and thalamus consisted of aperiodic waves with a frequency of 5-7 per second and an amplitude of 200-300 microvolts. The motor area was interrupted with short bursts of higher amplitude spikes (8-12 per second). 3. DFP was capable of evoking seizure patterns in all 4 areas, and usually in the following order: (a) thalamus, (b) caudate nucleus, (c) limbic cortex, and (d) motor cortex. 4. The motor cortex had the highest threshold and most frequently exhibited seizure waves when the other 3 areas were simultaneously engaged in hyperactivity. These facts suggested the necessity of a functional unity of the 4 cerebral areas for the participation of the motor cortex in seizures and may also explain the aura that precedes the attack. 5. Simultaneous activity between the caudate nucleus and the motor cortex suggested functional connections between these 2 areas. For the same reason the thalamus and limbic cortex appeared to have a physiologic relationship. 6. Spike and dome patterns were observed, most frequently in the thalamus. In some animals thalamic petit-mal-like patterns developed into frank grand-mal-like spikes. 7. Depression of convulsant activity without apparent shock suggests the depressant effect of acetylcholine in a concentration greater than that required for hyperactivity. This offers theoretical evidence for central transmission of acetylcholine.