The development of tolerance to morphine in the rat.
Tolerance to various effects of morphine in the rat can be quantified by means of a shift of semi-logarithmic dose-response curves. Tolerance to analgesia (hot plate, acetic acid writhing), catalepsy, and the tilted plane develops in a closely similar manner. Also, the stimulating effects of about 1 mg/kg morphine-HC1 tested in an open-field procedure are somewhat less pronounced in chronically treated rats than in naive ones. There is no correlation between tolerance development and the acute ED50 of different tests.
D000818:Animals; D004305:Dose-Response Relationship, Drug; D004361:Drug Tolerance; D006120:Grooming / Q000187:drug effects; D008297:Male; D009020:Morphine / Q000008:administration & dosage / Q000494:pharmacology*; D051381:Rats; D013997:Time Factors
D009020:Morphine