Little progress has been made in analyzing the brain mechanisms of offense behavior since 1979, when the senior author reviewed the literature on the subject (2). At that time it had been determined that electrical stimulation of various hypothalamic regions, especially the lateral hypothalamus, can produce offense (11, 21, 26), while lesions in the lateral hypothalamus abolish offense (1).
The lack of data on the neural organization of offense contrasts with its great importance in the life history of the animal. The behaviors of offense, including the bite-and-kick attack, offensive sideways posture, and chasing, are the basis of the territorial behavior of many animals, such as the rat (5). Another type of offense involving the same motor outputs but different motivational inputs has been called competitive fighting and occurs when animals fight over scarce food supplies (4).
The brain mechanisms of offense are clearly distinguishable from those of other aggression systems such as defense and predation. Earlier work was reviewed in the paper mentioned above (1), and since then it has been shown that ventromedial tegmental lesions abolish offense without affecting defense or predation (3).
The present study documents the production of offense from the anterior hypothalamus by chemical injection of picrotoxin, an antagonist of the inhibitory neurotransmitter GABA (gamma-amminobutyric acid). As far as we can determine, this is the first time that it has been possible to obtain offense behavior by chemical stimulation of specific locations in the brain.