Endogenous opioids inhibit early-stage pancreatic pain in a mouse model of pancreatic cancer

Molly A Sevcik ¹, Beth M Jonas , Theodore H Lindsay

⁰Neurosystems Center, Department of Diagnostic and Biological Sciences, University of Minnesota, Minneapolis, Minnesota 55455, USA.

Gastroenterology +

|

September 6, 2006

View abstract on PubMed

Summary

Endogenous opioids tonically modulate pancreatic cancer pain. Early-stage pancreatic cancer pain is masked but becomes apparent with opioid receptor antagonists, suggesting a CNS opioid mechanism.

Area Of Science

Neuroscience
Oncology
Pain Management

Background

The endogenous opioid system modulates pain, stress responses, and analgesia.
Human studies indicate tonic modulation of visceral pain.
The role of endogenous opioids in visceral cancer pain remains unclear.

Purpose Of The Study

To investigate the role of endogenous opioids in modulating pancreatic cancer pain.
To assess visceral pain behaviors in a mouse model of pancreatic cancer.

Main Methods

Utilized transgenic mice with spontaneous pancreatic cancer.
Assessed visceral pain behaviors including hunching and vocalization.
Administered central nervous system (CNS)-penetrant and non-penetrant opioid receptor antagonists.

Main Results

Late-stage pancreatic cancer mice showed spontaneous, morphine-reversible pain behaviors.
Early-stage mice lacked spontaneous pain behaviors.
CNS-penetrant antagonists (naloxone, naltrexone) induced pain behaviors in early-stage mice, but non-penetrant antagonists did not.

Conclusions

A CNS opioid-dependent mechanism tonically modulates pancreatic cancer pain.
Pain is masked in early stages and driven in later stages.
Understanding these mechanisms can improve pancreatic cancer diagnosis and treatment.

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