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|標題:||Orexin-A modulates glutamatergic NMDA-dependent spinal reflex potentiation via inhibition of NR2B subunit||作者:||Peng, H.Y.
|關鍵字:||spinal cord;pelvic nerve;urethra;rats;long-term potentiation;postinjury pain hypersensitivity;fiber-evoked;potentials;superficial dorsal horn;protein-kinase-c;anesthetized;rats;central sensitization;synaptic plasticity;receptor activation;hypothalamic area||Project:||American Journal of Physiology-Endocrinology and Metabolism||期刊/報告no：:||American Journal of Physiology-Endocrinology and Metabolism, Volume 295, Issue 1, Page(s) E117-E129.||摘要:||
Glucose-sensitive neurons in the lateral hypothalamic area produce orexin-A (OxA) as well as orexin-B (OxB) and send their axons to the spinal dorsal horn, which predominantly expresses orexin receptor-1 (OX-1), showing a higher sensitivity to OxA. The purpose of the present study was to assess the effects of OxA on the induction of a novel form of activity-dependent reflex potentiation, spinal reflex potentiation (SRP), in the pelvic-urethral reflex activity. External urethra sphincter electromyogram in response to pelvic afferent nerve test stimulation (TS; 1/30 Hz) or repetitive stimulation (RS; 1 Hz) was recorded in anesthetized rats. TS evoked a baseline reflex activity, whereas RS produced SRP, which was abolished by intrathecal OxA (30 nM, 10 mu l). Intrathecal SB-408124 (10 mu M, 10 mu l), an OX-1 antagonist, reversed the abolition on SRP caused by OxA. Although there is, so far, no NR2A-and NR2B-specific agonist available, N-methyl-D-aspartate (NMDA) reversed the abolition on the RS-induced SRP caused by the coadministration of OxA and Co-101244 (30 nM, 10 mu l; an NMDA NR2B subunit antagonist), but it did not reverse the abolition by the co-administration of OxA and PPPA (300 nM, 10 mu l; an NMDA NR2A subunit antagonist). In conclusion, the activation of descending orexinergic fibers may inhibit the repetitive afferent input-induced central sensitization of pelvic-urethral reflex activity and urethra hyperactivity, indicating that spinal orexinergic neural transmission may be a novel target for the treatment of patients with neuropathetic or postinflammatory pain of pelvic origin.
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