Reversible behavioral and electrographic manifestations induced by methionine sulfoximine

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Abstract
A threshold dose of MSI [methionine sulfoximine] produced episodic and background behavioral manifestations and electrographic manifestations of an entirely reversible nature. The reversibility was supported by the absence of mortality and status epilepticus and the entirely negative nature of the histopathological examination of the brains of animals used in this study. Two new nonepisodic behavioral manifestations were added to the known MSI syndrome: marked hyperphagic tendency in cats and transient hypothermia immediately before the onset of episodic running behavior in cats and rats. Episodic behavioral manifestations were fractionated into episodic running behavior (ERB), convulsion preceded by ERB (C-1), and convulsion independent from ERB (C-2). ERB was the most frequently observed episodic behavior pattern, either spontaneously or following sound stimulation. It was strikingly similar to that observed in genetically audiogenic-sensitive animals. Electrographically, ERB was coincident with a lower voltage, fast arousal pattern, and there was no postictal depression. Convulsion was less common than ERB. While C-1 was most clearly seen in rats, C-2 was more apparent in cats. There was some interspecies difference in the pattern of C-l. In the C-2 of cats, electrographic seizure discharge developed from the amygdala with subsequent involvement of both limbic and nonspecific structures. The possible significance of the reversible MSI syndrome as an experimental model for neurobiological exploration of innate behavior mechanisms are discussed.