Neuroscience letters
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Neuroscience letters · Sep 1996
Effects of transcutaneous electrical nerve stimulation (TENS) on spontaneous and noxiously evoked dorsal horn cell activity in cats with transected spinal cords.
Effects of transcutaneous electrical nerve stimulation (TENS) on spontaneous and noxiously evoked dorsal horn neurons were studied in alpha-chloralose anesthetized cats after spinal cords had been transected at the T12 segment. Previous work in cats with intact cords showed that TENS applications to somatic receptive fields could significantly reduce and maintain decreased dorsal horn cell activity. ⋯ The results demonstrated that spontaneously and noxiously evoked cell activities were reduced significantly during TENS and no significant difference was found between pre-TENS control activity and post-TENS application cell activity. This information implies that initial gating (reduction cell activity), which occurs during TENS applications, is due to a segmental effect.
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Neuroscience letters · Sep 1996
Novel receptor mechanisms for heroin and morphine-6 beta-glucuronide analgesia.
The rapid metabolism of heroin to 6-acetylmorphine and its slower conversion to morphine has led many to believe that heroin and morphine act through the same receptors and that the differences between them are due to their pharmacokinetics. We now present evidence strongly implying that heroin and two potent mu drugs, fentanyl and etonitazine, act through a unique receptor mechanism similar to morphine-6 beta-glucuronide which is readily distinguished from morphine. Heroin, 6-acetylmorphine and morphine-6 beta-glucuronide show no analgesic cross tolerance to morphine in a daily administration paradigm, implying distinct receptors. ⋯ Antisense mapping of the mu opioid receptor MOR-1 reveals that oligodeoxynucleotide probes against exon 2, which are inactive against morphine analgesia, block morphine-6 beta-glucuronide, heroin, fentanyl and etonitazine analgesia. Finally, an antisense probe targeting Gi alpha 1 blocks both heroin and morphine-6 beta-glucuronide, but not morphine, analgesia. These results indicate that heroin, 6-acetylmorphine, fentanyl and etonitazine all can produce analgesia through a novel mu analgesic system which is similar to that activated by morphine-6 beta-glucuronide.