Effects of diazepam on extinction induced aggression in pigs.

Pigs were trained to press a panel with their snout to get food in an operant conditioning chamber. Aggressive behaviour which developed between two pigs submitted together to extinction was used as a baseline to study the effects of 1-2 mg/kg diazepam. When access to the response panel and feeding area was permitted, diazepam enhanced resistance to extinction and did not modify aggression. When access to the response panel and feeding area was not permitted, diazepam increased the severity of aggression observed between the animals. In both instances, plasma corticosteroid levels were depressed in diazepam-treated pigs. These results suggest that benzodiazepines do not act on frustation or aggressiveness per se, but rather strengthen the prevailing behavioural attitudes in the animals' repertoire at the time of test.