1978 Volume 37 Issue 1 Pages 6-12
To analyze the correlation between change in the activity of a rabbit's hippocampus and eye movements induced by repeated electric stimulation of the brain, agents such as a cholinergic agent (carbachol) and an adrenergic agent (adrenaline), were injected into the hippocampus through a thin steel tube which had been inserted when the rabbit was under Pentobarbital anaesthesia. The injections were given before and after 10 electric stimulations of a rabbit's hippocampus, and resulting changes in the activity of the brain and ocular reflex were measured using the EEG's and ENG. Electrical stimulus used herein was 1msec., 200Hz pulse waves at 3 volts for 30 seconds. This amount of stimulus was given once a day for ten days. The following results were obtained;
(1) The hippocampus produced two types of nystagmus in response to the agents mentioned above. One was a nystagmus which appeared shortly after injection of a cholinergic agent into a normal rabbit's hippocampus. Such was horizontal and directed to the side of the injection. The other was a nystagmus which appeared with a fairly long latency and was directed to the right and left. Such mainly appeared in an animal given repeated electric stimulation of the hippocampus when an adrenergic agent was given. However, on injection of a cholinergic agent into a normal rabbit's hippocampus, such also appeared in parallel with a rebound in the EEG's.
Both types of nystagmus appeared on the basis of an arousal state in the EEG's. However, the latter type of nystagmus was always preceeded by marked seizure discharges covering the hippocampus, mid-brain reticular formation and neocortex.
(2) As a result of repeated electric stimulation of a rabbit's hippocampus, it was found that excitability of the hippocampus in response to a cholinergic agent decreased, while that in response to an adrenergic agent increased.
