Kathleen Berry-Hebert’s thesis to get her Masters in Psychology at the University of Houston Clear-Lake was titled “Analog of Neuropeptide FF attenuates morphine tolerance.” Previous studies suggest that neuropeptide FF (NPFF) plays a role in opiate dependence. Endogeneous NPFF also appears to play a role in opiate tolerance because the third ventricle injection of IgG from NPFF antiserum selectively restores morphine sensitivity in morphine-tolerant rats. The NPFF analog, desaminoYFLFQPQRamide (daY8Ra) has behavioral effects of NPFF and has reduced morphine dependence! That is pretty crucial information in itself.
This study assessed whether daY8Ra could also attenuate morphine tolerance. Third ventricle injection of daY8Ra restored the analgesic response to the morphine in morphine-tolerant rats. Analgesia is the feeling of relief of pain, the feeling experienced from morphine. The pain the rats endured was from heat on their tail, the radiant heat tail flick test. Saline injection failed to produce the analgesic effect. In opiate-naïve rats, the same daY8Ra treatment did not affect the analgesic response to injected morphine. In conclusion, the daY8Ra appears to selectively restore morphine sensitivity opiate-tolerant animals, further supporting the theory that endogenous NPFF contributes to opiate tolerance.
J. R. Lake, K. Payza, K. D. Deshotel, D. D. Hausam, and W. E. Witherspoon contributed to this in addition to Kathleen Berry-Hebert. It was published in Neuroscience Letters in 1992 and Nature, a world-renowned science journal.