Electroencephalographic and behavioral changes in unrestrained rabbits during insulin hypoglycemia

Abstract

The earliest changes in the eeg during insulin hypoglycemia consisted of depressed activity in the olfactory bulb and hippocampus, together with generalized slowing and irregular spiking in the amygdala, septum, and olfactory tubercle. Increased threshold of hippocampal arousal correlated temporally with the appearance of "delta waves" in the cortical eeg. Behaviorally, the animal first became ataxic and then gradually became semicomatose before motor convulsion. Subcortical electrical seizure activity was observed during prolonged hypoglycemia and did not appear to involve the cortex. Eeg changes persisting for several days were noted in the hippocampus, olfactory bulb, and olfactory tubercle. A case of apparently permanent electrical change in the amygdala is described. Comparison of Metrazol (isoniazid) and electroshockwith insulin treatment shows that the eeg changes in the former resemble early hypoglycemia, whereas those of the latter resemble prolonged hypoglycemia. These results are discussed in terms of the possible site of action of insulin hypoglycemia and in relation to the therapeutic efficacy of this treatment.