Reports

Morphine: Single-Dose Tolerance

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Science  29 Nov 1968:
Vol. 162, Issue 3857, pp. 1011-1012
DOI: 10.1126/science.162.3857.1011

Abstract

Rats show a significant degree of tolerance to a second dose of morphine, with the degree of tolerance increasing the longer the delay between the two doses of morphine. To measure the morphine effect a foot-shock attenuation procedure that allowed the animal to adjust the shock intensity was used in studying delays of up to 180 days.