Induction of 'rage' following microinjections of glutamate into midbrain but not hypothalamus of cats.

Microinjections of glutamic acid were made into the same midbrain and hypothalamic sites of cats at which 'defensive-rage' behaviour was elicited by electrical stimulation. It was found that : (1) medial hypothalamic and midbrain tegmental glutamate injections were without behavioural effect; (2) midbrain periaqueductal grey injections elicited a 'rage' display. Since glutamate depolarizes cell bodies but not axons, the results suggest that there is a specific population of neurones in the midbrain whose excitation elicits this reaction.