Potentiating effect of morphine on oral salmonella enterica serovar typhimurium infection is μ-opioid receptor-dependent

Jessica M. Breslow, Pu Feng, Joseph J. Meissler, John E. Pintar, John Gaughan, Martin W. Adler, Toby K. Eisenstein

Research output: Contribution to journalArticle

11 Scopus citations


Previous studies from our laboratory demonstrated that mice treated with morphine pellets are sensitized to Salmonella enterica, serovar Typhimurium infection. However, the opioid receptor antagonist, naltrexone, only partially blocked the effect of morphine, raising the possibility that the opioid might have some of its effects through a nonopioid receptor. To further clarify whether sensitization to infection is an opioid receptor-dependent phenomenon, μ-opioid receptor knockout (MORKO) mice were used in the present study. Wild-type (WT) and MORKO mice were treated with morphine and their sensitivity to oral Salmonella infection was assessed by mortality, bacterial burdens in gut associated lymphoid tissue and in blood and peritoneal fluid, and by levels of pro-inflammatory cytokines in plasma. MORKO animals treated with morphine were refractory to a sublethal dose of Salmonella, while similar treatment of WT animals resulted in 100% mortality. WT animals treated with morphine had high bacterial loads in all organs tested, while morphine-treated MORKO animals had no culturable Salmonella in any organs. Pro-inflammatory cytokine levels were elevated in morphine-treated WT but not MORKO mice infected with Salmonella. These results provide definitive evidence that the morphine-mediated enhancement of oral Salmonella infection is dependent on the μ-opioid receptor.

Original languageEnglish (US)
Pages (from-to)330-335
Number of pages6
JournalMicrobial Pathogenesis
Issue number6
StatePublished - Dec 1 2010


All Science Journal Classification (ASJC) codes

  • Microbiology
  • Infectious Diseases


  • Opioids
  • Salmonella
  • μ-Opioid receptor

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