Infundibular ACTH can be excluded as a critical mediator in social behaviours

Kainic acid lesions of the infundibulum resulted in a significant decrease in infundibular ACTH concentrations. However, the lesioned rats did not differ from the vehicle-injected controls in a social interaction test, in their latency to start drinking in a novel environment, or in their aggressive behaviour in home-cage intruder tests. It can therefore be concluded that endogenous infundibular ACTH does not play a significant role in these behaviours. This can be contrasted with the effects of exogenously administered ACTH which has previously been shown to reduce social interaction and increase aggression. Both the lesioned rats and the controls showed decreased social interaction after ACTH administration, and therefore the infundibulum can be excluded as a critical site of action of exogenous ACTH in mediating this behavioural change.