Analgesic effect of intrathecally administered orexin-A in the rat formalin test and in the rat hot plate test
Autor: | Tatsuo Yamamoto, Natsuko Nozaki-Taguchi, Tanemichi Chiba |
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Rok vydání: | 2002 |
Předmět: |
Pharmacology
medicine.medical_specialty medicine.drug_class business.industry digestive oral and skin physiology Receptor antagonist Spinal cord Orexin Orexin-A Nociception Endocrinology medicine.anatomical_structure SB-334867 nervous system Dorsal root ganglion Internal medicine mental disorders medicine Hot plate test business hormones hormone substitutes and hormone antagonists psychological phenomena and processes |
Zdroj: | British Journal of Pharmacology. 137:170-176 |
ISSN: | 0007-1188 |
DOI: | 10.1038/sj.bjp.0704851 |
Popis: | 1. Orexin-A and orexin-B (also known as hypocretin-1 and hypocretin-2) are hypothalamic peptides and regulate feeding behaviour, energy metabolism and the sleep-wake cycle. Orexin-A binds equally to both orexin-1 and orexin-2 receptors, while orexin-B has a preferential affinity for orexin-2 receptors. 2. Orexins are also known to be concentrated in superficial laminae of the spinal dorsal horn, and orexin-A and orexin-1 receptors are found in the dorsal root ganglion cells. 3. In the present study, the authors examined the effect of intrathecal injection of either orexin-A or orexin-B in the rat formalin test (a model of inflammatory pain) and in the rat hot plate test. The paw formalin injection induces biphasic flinching (phase 1: 0-6 min; phase 2: 10-60 min) of the injected paw. 4. Intrathecal injection of orexin-A, but not orexin-B, decreased the sum of flinches in phases 1 and 2 in the formalin test and increased the hot plate latency. These effects of orexin-A were completely antagonized by pre-treatment with SB-334867, a selective orexin-1 receptor antagonist. Intrathecal injection of SB-334867 alone had no effect in the formalin test or in the hot plate test. 5. Intrathecal injection of orexin-A suppressed the expression of Fos-like immunoreactivity (Fos-LI), induced by paw formalin injection, in laminae I-II of L4-5 of the spinal cord. 6. These data suggest that the spinal orexin-1 receptor is involved in the nociceptive transmission and that the activation of the spinal orexin-1 receptor produces analgesic effects in the rat formalin test and in the rat hot plate test. |
Databáze: | OpenAIRE |
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