EFFECTS OF LITHIUM INJECTIONS INTO AMYGDALA AND HIPPOCAMPUS OF AWAKE MONKEYS

In unanesthetized rhesus monkeys equipped with intracerebral chemitrodes (push-pull cannulae plus multiple contacts), injections of lithium chloride into the amygdala-hippocampus region produced high-voltage, 1/sec sharp waves, and episodes of electrical afterdischarges without motor manifestations. The effect, which began after a delay of a few minutes, was strictly localized to the injection site and lasted for minutes or hours. No change in motor thresholds was observed, but afterdischarge thresholds increased considerably. Spontaneous restlessness and aggressiveness of the animals were diminished. After pretreatment with lithium, when the local electrical disturbance had subsided, residual effects were demonstrated by injection of (a) l-glutamate, which produced a reappearance of typical lithium waves; or (b) acetylcholine, which produced a mixture of lithium and acetylcholine waves. After pre-treatment with l-glutamate, when its characteristic effects had subsided, injection of lithium re-activated the mechanism for producing afterdischarges resembling those of glutamate. We suggest that the well-known excitatory properties of l-glutamate and acetylcholine on CNS neurons may be related to a selective increase in membrane permeability to sodium or lithium if present. Therapeutic effects of lithium may be related to its specific effect on the limbic system. © 1969.