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Partial agonists of the morphine type: facilitative effects on electrophysiologically recorded C-fiber reflexes in
1National Institute on Drug Abuse, Addiction Research Center, Baltimore, MD 21224.
Abstract:
The purpose of the present study was to examine the effects of the partial agonists of the morphine type, buprenorphine, profadol and propiram on the spinally-mediated C-fiber reflex. Buprenorphine, profadol and propiram facilitated the C-fiber reflex. In the presence of naltrexone, the effects of buprenorphine were changed to depression of the C-fiber reflex. Profadol and propiram continued to facilitate the C-fiber reflex in the presence of naltrexone. The present results suggest that buprenorphine facilitated the C-fiber reflex by blocking endogenous opioid peptide inhibition of the C-fiber reflex whereas profadol and propiram facilitated it by a non-opioid mechanism.