Estimation of the dissociation constant of naloxone in the naive and morphine-tolerant guinea-pig isolated ileum: Analysis by the constrained schild plot

Ronald J. Tallarida, Mary Jane Robinson, Frank Porreca, Alan Cowan

Research output: Contribution to journalArticle

6 Scopus citations


The pA2 values for naloxone-morphine were determined using ilea taken from naive and morphine-tolerant guinea-pigs. This constant decreased from 8.56 (±0.22) in the naive to 7.95 (±0.12) in tolerant tissues. The values of the pA2's were based on Schild plots using conventional regression techniques; this regression resulted in values of -log KB of 8.79 (±1.5) and 8.18 (±1.2) in naive and morphine-tolerant ilea, respectively. While pA2 differed, the difference in -log KB was not statistically significant. Since these two values are theoretically equivalent, the above finding appears paradoxical. Constraining the slope of the Schild plot to the theoretically required -1 resolved this discrepancy by reducing the error inherent in the calculation of -log KB determined by conventional regression.

Original languageEnglish (US)
Pages (from-to)1691-1694
Number of pages4
JournalLife Sciences
Issue number16-17
StatePublished - Jan 1 1982
Externally publishedYes


ASJC Scopus subject areas

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

Cite this