Methadone-induced behavioral changes: circular movements, aggression, and electrophysiological aspects.

Behavioral changes are induced in animals by methadone administration. The dose-dependent CM effect is present 2 to 3 minutes after methadone administration. This effect can be partially blocked by nalline. A Complete blockade occurs when the naline-reserpine combination is given prior to the administration of methadone. Atropine sulfate dose not block the CM effect. Methadone withdrawal produces mild symptoms of aggression, and they can be intensified by amphetamine and apomorphine. During the process of development of tolerance and addiction, electrophysiological changes are produced. These changes can be intensified by apomorphine treatment in the methadone-withdrawal animals. On the basis of pharmacological manipulation in our experimental conditions, the involvement of cerebral biogenic amines, especially dopamine, is proposed.