Tolerance to morphine-induced mydriasis in the rat pupil

Charles H. Adler, Michael Robin, Martin W. Adler

Research output: Contribution to journalArticlepeer-review

9 Scopus citations


Despite the commonly held view that tolerance does not develop to the pupillary effects of narcotics, recent studies have demonstrated tolerance to heroin-induced miosis in humans and to morphine-induced mydriasis in the mouse. Previous studies in this laboratory have shown that morphine produces a dose-related mydriasis and fluctuation (large amplitude, irregular oscillations in pupil diameter) in the rat pupil; the present study was designed to determine if tolerance develops to these effects following subcutaneous implantation of morphine pellets. We found that there is, indeed, tolerance to the morphine-induced mydriasis, but it is not complete. Furthermore, statistically significant tolerance does not develop to morphine-induced fluctuations in the rat pupil.

Original languageEnglish (US)
Pages (from-to)2469-2475
Number of pages7
JournalLife Sciences
Issue number22
StatePublished - Jun 1 1981

ASJC Scopus subject areas

  • Biochemistry, Genetics and Molecular Biology(all)
  • Pharmacology, Toxicology and Pharmaceutics(all)


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