Involvement of Supraspinal Imidazoline Receptors and Descending Monoaminergic Pathways in Tizanidine-Induced Inhibition of Rat Spinal Reflexes
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- Kino Yurika
- Laboratory of CNS Pharmacology, Graduate School of Pharmaceutical Sciences, Nagoya City University
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- Tanabe Mitsuo
- Laboratory of CNS Pharmacology, Graduate School of Pharmaceutical Sciences, Nagoya City University
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- Honda Motoko
- Laboratory of CNS Pharmacology, Graduate School of Pharmaceutical Sciences, Nagoya City University
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- Ono Hideki
- Laboratory of CNS Pharmacology, Graduate School of Pharmaceutical Sciences, Nagoya City University
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Abstract
The neuronal pathways involved in the muscle relaxant effect of tizanidine were examined by measurement of spinal reflexes in rats. Tizanidine (i.v. and intra-4th ventricular injection) decreased the mono- and disynaptic (the fastest polysynaptic) reflexes (MSR and DSR, respectively) in non-spinalized rats. Depletion of central noradrenaline by 6-hydroxydopamine abolished the depressant effect of tizanidine on the MSR almost completely and attenuated the effect on the DSR. Co-depletion of serotonin by 5,6-dihydroxytryptamine and noradrenaline resulted in more prominent attenuation of tizanidine-induced inhibition of the DSR. Supraspinal receptors were then studied using yohimbine- and some imidazoline-receptor ligands containing an imidazoline moiety. Idazoxan (I1, I2, I3, and α2), efaroxan (I1, I3, and α2), and RX821002 (I3 and α2), but not yohimbine, an α2-adrenergic receptor antagonist with no affinity for I receptors, antagonized the inhibitory effects of tizanidine. Thus, supraspinal I receptors (most likely I3) and descending monoaminergic influences are necessary for tizanidine-induced inhibition of spinal segmental reflexes.<br>
Journal
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- Journal of Pharmacological Sciences
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Journal of Pharmacological Sciences 99 (1), 52-60, 2005
The Japanese Pharmacological Society
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Details 詳細情報について
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- CRID
- 1390001205176706304
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- NII Article ID
- 10025730341
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- NII Book ID
- AA11806667
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- ISSN
- 13478648
- 13478613
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- NDL BIB ID
- 7436883
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- PubMed
- 16127244
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- Text Lang
- en
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- Data Source
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- JaLC
- NDL
- Crossref
- PubMed
- CiNii Articles
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- Abstract License Flag
- Disallowed