Stereotyped behaviour in animals induced by stimulant drugs or by a restricted cage environment: relation to disintegrated behaviour, brain dopamine and psychiatric disease.

Stereotyped behaviour can be produced in animals both by stimulant drugs (amphetamine, methamphetamine, cocaine, etc.) and by a restricted cage environment. Strong evidence indicates that the effect of stimulant drugs is mediated through a primary effect on brain dopamine, and further knowledge is now being acquired through studies on dopamine receptors, tolerance and reverse tolerance to amphetamines and the neural connections of dopaminergic sub-systems with other sub-systems in the brain. The forms of stereotypy induced by a restricted cage environment have been compared with other effects of this type of environment on behaviour and general health. This has led to a hypothesis that stereotyped behaviour may function as a survival (or defence) strategy in an unfavourable milieu. Some evidence indicates that brain dopamine is also involved in the mediation of stereotyped behaviour induced by the environment. The relevance of these results in clinical psychiatry is discussed. Stereotypy (and related disintegrated behaviour) is a well known feature of several mental diseases.