European journal of pain : EJP
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Comparative Study
Intrathecal antinociceptive interaction between the NMDA antagonist ketamine and the opioids, morphine and biphalin.
Biphalin is an opioid peptide analogue that currently is under clinical development as a new type of site-directed analgesic. In rats, the intrathecal (i.t.) analgesic potency of biphalin is 1000-fold greater than morphine. Such a high activity may reflect this compound's activation of three types of opioid receptors (mu, delta and kappa). ⋯ Co-administration of ketamine with biphalin or morphine produced markedly greater antinociception than biphalin or morphine alone in acute, thermal tail flick testing. These results suggest that NMDA antagonists may be useful potentiators of biphalin analgesia. Thus, to obtain the same spinal antinociceptive effect, lower doses of biphalin or morphine are required when ketamine is co-administered.
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Because of its severity, chronicity, resistance to usual therapy and its consequences on quality of life, neuropathic pain represents a real clinical challenge. Fundamental research on this pathology uses metabolic, pharmacological or traumatic models in rodents that reproduce the characteristic human pain symptoms. In 1996, Mosconi and Kruger morphologically described a model of peripheral neuropathy in which a cuff of polyethylene tubing was placed around the sciatic nerve in rats. ⋯ The analysis of video recordings revealed that most aspects of spontaneous behavior remained unaffected on the long term, excepted for a decrease in the time spent at social interaction for the neuropathic mice. Using the elevated plus-maze and the marble-burying test, we also showed that neuropathic mice develop an anxiety phenotype. Our data indicate that sciatic nerve cuffing in mice is a pertinent model for the study of nociceptive and emotional consequences of sustained neuropathic pain.