A system for allowing animals to self administer drugs via intranasal absorption. The system comprises an aerosol dispersing apparatus (1) connected to a source of pressurized air (5) for ejecting a pharmaceutical composition contained in a reservoir (8) out of the aerosol dispersing apparatus nozzle head (3) and into a sensing chamber (12) when a sensor (16) detects the presence of an animal in the sensing chamber (12). The system can be used to study the addictiveness of new drugs as well as providing a model system for small animals, such as the mouse, to studying behavioral and physiological responses to addictive drugs.