Abstract

Morphine solutions were the only drinking solutions available to mice for 13 days. During the last 9 days of drinking a 1.0 mg/ml of morphine solution, the mice averaged a daily morphine intake of approximately 150 mg/kg. When injected with naloxone, the mice showed characteristic abstinence jumping, diarrhea, weight loss and abnormal posturing, suggesting that physical dependence had been produced by the morphine ingestion.