PubMed · 4202213
The source did not provide an abstract. Follow the original record for more information.
Explore connections, maps & timelines
H H Ong, T O-Ishi, E L May. 1974. Phenylmorphan agonists-antagonists.. https://doi.org/10.1021/jm00247a026
Cite the original work for its findings. Save a collection to share your selection of sources.
KEEP EXPLORING
The neuropeptide neurotensin (NT) elicits hypothermic and naloxone-insensitive analgesic responses after brain injection. Recent pharmacological evidence obtained with NT agonists and antagonists suggests that these effects are mediated by a receptor distinct from the initially cloned high-affinity NT receptor (NTR1). The recent cloning of a second NT receptor (NTR2) prompted us to evaluate its role in NT-induced analgesia. Intracerebroventricular injections in mice of two different antisense oligodeoxynucleotides from the NTR2 markedly decreased NTR2 mRNA and protein and reduced NT-induced analgesia. This effect was specific, because NTR1 levels were unaffected, and sense or scramble oligodeoxynucleotides had no effect. Structure-activity studies revealed a close correlation between the analgesic potency of NT analogs and their affinity for the NTR2 and disclosed potent and selective agonists of this receptor. These data confirm that NTR1 is involved in the NT-elicited turning behavior and demonstrate that the NTR2 mediates NT-induced analgesia.
Neuropathic pain syndromes are one of the major problems of cancer pain treatment. The present study surveys 593 cancer patients treated by a pain service following the WHO guidelines for relief of cancer pain. Of these, 380 presented with nociceptive, 32 with neuropathic and 181 with mixed (nociceptive and neuropathic) pain. In patients with nociceptive, mixed and neuropathic pain, the average duration of evaluated pain treatment was 51, 53 and 38 days, respectively. Non-opioid or opioid analgesics were given to 99%, 96% and 79%, antidepressants to 8%, 25% and 19%, anticonvulsants to 2%, 22% and 38% and corticosteroids to 26%, 35% and 22% of patients, respectively. Systemic analgesia was supported by palliative antineoplastic treatment (48%, 56% and 38% of patients), nerve blocks (3%, 6% and 6%), psychotherapy (3%, 7% and 3%), physiotherapy (6%, 12% and 13%) and transcutaneous electric nerve stimulation (1%, 6% and 6%). Analgesic treatment resulted in a significant pain relief in all groups of patients, as the mean pain intensity (NRS) decreased from 66 (nociceptive), 65 (mixed) and 70 (neuropathic) on admission to 26, 30 and 28 after 3 days and 18, 17 and 21 at the end of survey. The total outcome of pain treatment was not predicted by the designation to nociceptive, mixed or neuropathic pain. In conclusion, neuropathic cancer pain is not intractable and can be relieved in the majority of patients by treatment following the WHO guidelines.
Agonist-induced down-regulation of opioid receptors appears to require the phosphorylation of the receptor protein. However, the identities of the specific protein kinases that perform this task remain uncertain. Protein kinase C (PKC) has been shown to catalyze the phosphorylation of several G protein-coupled receptors and potentiate their desensitization toward agonists. However, it is unknown whether opioid receptor agonists induce PKC activation under physiological conditions. Using cultured SH-SY5Y neuroblastoma cells, which naturally express mu- and delta-opioid receptors, we investigated whether mu-opioid receptor agonists can activate PKC by measuring enzyme translocation to the membrane fraction. PKC translocation and opioid receptor densities were simultaneously measured by 3H-phorbol ester and [3H]diprenorphine binding, respectively, to correlate alterations in PKC localization with changes in receptor binding sites. We observed that mu-opioid agonists have a dual effect on membrane PKC density depending on the period of drug exposure. Exposure for 2-6 h to [D-Ala2,N-Me-Phe4,Gly-ol]enkephalin or morphine promotes the translocation of PKC from the cytosol to the plasma membrane. Longer periods of opioid exposure (>12 h) produce a decrease in membrane-bound PKC density to a level well below basal. A significant decrease in [3H]diprenorphine binding sites is first observed at 2 h and continues to decline through the last time point measured (48 h). The opioid receptor antagonist naloxone attenuated both opioid-mediated PKC translocation and receptor down-regulation. These results demonstrate that opioids are capable of activating PKC, as evidenced by enhanced translocation of the enzyme to the cell membrane, and this finding suggests that PKC may have a physiological role in opioid receptor plasticity.