Opiate receptor thermodynamics: Agonist and antagonist binding

Robert Hitzemann, Maureen Murphy, James Curell

Research output: Contribution to journalArticle

22 Scopus citations


The equilibrium thermodynamics of [3H]etorphine and [3H]diprenorphine binding to rat brain membranes were studied. In the absence of NaCl, the binding of [3H]etorphine was endothermic (ΔH° = +2.31 kcal/mol) and driven by a large increase in entropy (ΔH° = +51.8 e.u.). Under similar conditions, the binding of [3H]diprenorphine was exothermic (ΔH° = - 2.78 kcal/mol). In the presence of 100 mM Nacl, [3H]etorphine binding was relatively isothermic (ΔH° = +0.61 kcal/mol) and driven by a large increase in entropy ΔS° = +45.6 e.u.). NaCl significantly decreased both ΔH° (-2.78 to -7.48 kcal/mol) and ΔS° (33.0 to 18.5 e.u.) for [3H]diprenorphine binding. The data suggest that the agonist configuration of the opiate receptor exists in a more open and mobile (higher entropy) conformation than does the antagonist form of the receptor.

Original languageEnglish (US)
Pages (from-to)171-177
Number of pages7
JournalEuropean Journal of Pharmacology
Issue number2
Publication statusPublished - Jan 22 1985
Externally publishedYes



  • Diprenorphine
  • Etorphine
  • Opiates
  • Receptor
  • Thermodynamics

ASJC Scopus subject areas

  • Cellular and Molecular Neuroscience
  • Pharmacology

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