Effects of Delta-Opioid Receptor Activation in Morphine Tolerant Rats
Author Information
Author(s): Michael M. Morgan, Ashley Michelle D., Ingram Susan L., Christie MacDonald J.
Primary Institution: Washington State University Vancouver
Hypothesis
The movement of delta-opioid receptors to the membrane will allow antinociception to the DOR agonist deltorphin II as a way to compensate for morphine tolerance.
Conclusion
Chronic morphine administration alters delta-opioid receptors in the vPAG, but activation of these receptors does not compensate for the decrease in antinociception caused by morphine tolerance.
Supporting Evidence
- Chronic morphine administration shifts delta-opioid receptors from the cytoplasm to the plasma membrane.
- Microinjection of deltorphin into the vPAG produced a mild antinociception that did not vary consistently across morphine pretreatment doses.
- Activation of delta-opioid receptors did not appear to compensate for the decrease in antinociception caused by morphine tolerance.
Takeaway
When rats get used to morphine, a drug that helps with pain, another drug called deltorphin doesn't help them feel less pain like it should.
Methodology
Male Sprague-Dawley rats were made tolerant to morphine through repeated injections or pellet implantation, followed by microinjection of deltorphin into the vPAG to assess antinociceptive and locomotor effects.
Limitations
The study may not fully capture the complexity of opioid receptor interactions and their effects on behavior.
Participant Demographics
Male Sprague-Dawley rats, weighing 240–360 g.
Statistical Information
P-Value
p<0.05
Statistical Significance
p<0.05
Digital Object Identifier (DOI)
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