Morphine tolerance in genetically selected rats induced by chronically elevated saccharin intake

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Science  26 Aug 1983:
Vol. 221, Issue 4613, pp. 871-873
DOI: 10.1126/science.6879185


Rats of line LC2-Hi that drank about 50 milliliters of a highly palatable saccharin solution daily for 28 consecutive days did not show morphine analgesia or an opioid form of stress-induced analgesia and were not responsive to naloxone. These findings support the idea that chronically elevated saccharin intake may cause increased release and utilization of endogenous opiates.