Behavioral consequences of delta-opioid receptor activation in the periaqueductal gray of morphine tolerant rats

Michael M. Morgan, Michelle D. Ashley, Susan Ingram, MacDonald J. Christie

Research output: Contribution to journalArticle

14 Citations (Scopus)

Abstract

Chronic morphine administration shifts delta-opioid receptors (DORs) from the cytoplasm to the plasma membrane. Given that microinjection of morphine into the PAG produces antinociception, it is hypothesized that the movement of DORs to the membrane will allow antinociception to the DOR agonist deltorphin II as a way to compensate for morphine tolerance. Tolerance was induced by twice daily injections of morphine (5, 10, or 20 mg/kg, subcutaneous) for 3.5 days. Microinjection of deltorphin into the vPAG 6 hours after the last morphine injection produced a mild antinociception that did not vary in a consistent manner across morphine pretreatment doses or nociceptive tests. In contrast, deltorphin caused a decrease in activity in morphine tolerant rats that was associated with lying in the cage. The decrease in activity and change in behavior indicate that chronic morphine administration alters DORs in the vPAG. However, activation of these receptors does not appear to compensate for the decrease in antinociception caused by morphine tolerance.

Original languageEnglish (US)
Article number516328
JournalNeural Plasticity
Volume2009
DOIs
StatePublished - 2009
Externally publishedYes

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Periaqueductal Gray
delta Opioid Receptor
Morphine
Microinjections
Injections
Cytoplasm
Cell Membrane
Membranes

ASJC Scopus subject areas

  • Neurology
  • Clinical Neurology

Cite this

Behavioral consequences of delta-opioid receptor activation in the periaqueductal gray of morphine tolerant rats. / Morgan, Michael M.; Ashley, Michelle D.; Ingram, Susan; Christie, MacDonald J.

In: Neural Plasticity, Vol. 2009, 516328, 2009.

Research output: Contribution to journalArticle

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