[Rat behavior in an "open field" when chronically administered morphine]

15-day long administration of morphine in doses of 20 to 120 mg/kg, injected twice daily produced initially a depression followed by an increased locomotor activity, more pronounced grooming behavior and less so--rearing. Abnormal forms of behavior like combined arrests and rapid movements, circling, stereatyped gnawing were also observed. Abstinence provoked by withdrawal of morphine or nalophine was characterized predominantly by the stimulation of locomotion and grooming with depressed rearing.