Date of Award


Degree Type


Degree Name


Degree Program




Major Professor

Soignier, Rodney Denis

Second Advisor

LaHoste, Gerald J.

Third Advisor

Daniel, Jill M.


Opioid medications are medicine's best weapon against severe intractable pain, but prolonged use of these medications can be complicated by side effects like tolerance and mental clouding which, themselves, can be disabling. The present study examined the independent and combined effects of inflammatory pain and opioid medication on spatial memory for a well learned task in Sprague-Dawley rats. The Hargreaves method was used to verify the pain state of the animals after complete Freund's adjuvant injection and morphine treatment. Whereas pain had little effect on spatial memory, morphine had profound detrimental effects that persisted beyond the analgesic effectiveness of the drug. However, morphine-induced cognitive deficits were absent when morphine was provided to animals in chronic pain. Also, analgesic tolerance was significantly attenuated in these animals. Taken together, these results suggest that chronic pain activates a neural mechanism that antagonizes the unwanted effects of opioids.


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