The Peripheral Versus Central Antinociception of a Novel Opioid Agonist: Acute Inflammatory Pain in Rats.

Opioid analgesics devoid of central side effects are unmet medical need in the treatment of acute pain (e.g. post-operative pain). Recently, we have reported on 14-O-methylmorphine-6-O-sulfate (14-O-MeM6SU), a novel opioid agonist of high efficacy producing peripheral antinociception in subchronic inflammatory pain in certain doses. The present study focused on the antinociceptive effect of 14-O-MeM6SU compared to morphine in formalin test of an early/acute (Phase I) and late/tonic (Phase II) pain phases. Subcutaneous 14-O-MeM6SU (253-1012 nmol/kg) and morphine (3884-31075 nmol/kg) dose dependently reduced the pain behaviors of both phases. Co-administered naloxone methiodide (NAL-M), a peripherally acting opioid antagonist, abolished the antinociceptive effect of 506 nmol/kg 14-O-MeM6SU. On the other hand, the effects of 14-O-MeM6SU (1012 nmol/kg) and morphine (15538 nmol/kg) were only partially affected by NAL-M, indicating the contribution of CNS to antinociception. Locally injected test compounds into formalin treated paws caused antinociception in both phases. Locally effective doses of test compounds were also injected into contralateral paws. Morphine showed effects in both phases, 14-O-MeM6SU in certain doses failed to produce antinociception in either phase. A NAL-M reversible systemic dose of 14-O-MeM6SU and the lowest systemic effective dose of morphine were evaluated for their sedative effects following isoflurane-induced sleeping (righting reflex). In contrast to morphine, 14-O-MeM6SU in certain antinociceptive doses showed no impact on sleeping time. These data highlight that high efficacy opioids of limited CNS penetration in certain doses mitigate somatic and inflammatory pain by targeting MOR at the periphery

Quantitative imaging biomarkers in neuro-oncology

Conventional structural imaging provides limited information on tumor characterization and prognosis. Advances in neurosurgical techniques, radiotherapy planning and novel drug treatments for brain tumors have generated increasing need for reproducible, noninvasive, quantitative imaging biomarkers. This review considers the role of physiological MRI and PET molecular imaging in understanding metabolic processes associated with tumor growth, blood flow and ultrastructure. we address the utility of various techniques in distinguishing between tumors and non-neoplastic processes, in tumor grading, in defining anatomical relationships between tumor and eloquent brain regions and in determining the biological substrates of treatment response. Much of the evidence is derived from limited case series in individual centers. Despite their `added value', the effect of these techniques as an adjunct to structural imaging in clinical research and practice remains limited