Document Detail


Effect of the centrally acting muscle relaxant tizanidine on spinal reflexes: involvement of descending noradrenergic systems.
MedLine Citation:
PMID:  7901443     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
Experiments were performed on intact and spinalized rats anesthetized with urethane and alpha-chloralose. In intact rats, administration of tizanidine (0.1 mg/kg, i.v.) decreased the mono- (MSR) and polysynaptic reflex potentials (PSR). Blood pressure was initially elevated and then lowered by tizanidine. Although pretreatments with hexamethonium and phentolamine prevented the tizanidine-induced decrease in blood pressure, the depressant effects of tizanidine on the reflexes remained. The alpha 2-antagonist idazoxan inhibited the tizanidine-induced decrease in spinal reflexes, suggesting that central alpha 2-adrenoceptors are involved in the depression of the reflexes. In spinalized rats, tizanidine transiently increased the MSR and gradually decreased the PSR. Blood pressure was elevated transiently by tizanidine. Although the hypertensive effect of tizanidine was inhibited by phentolamine, the effect of tizanidine on the PSR did not change. Prazosin blocked the stimulatory effect of tizanidine on the MSR and caused a rapid decrease of the PSR, suggesting that spinal alpha 1-adrenoceptors are involved in the enhancement of the reflexes. These results suggest that the depressant effects of tizanidine on spinal reflexes are due to the supraspinal and spinal effects of the drug, and not to changes in blood pressure.
Authors:
H Ono; C Fukushima; H Fukuda
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Japanese journal of pharmacology     Volume:  62     ISSN:  0021-5198     ISO Abbreviation:  Jpn. J. Pharmacol.     Publication Date:  1993 Aug 
Date Detail:
Created Date:  1993-12-10     Completed Date:  1993-12-10     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  2983305R     Medline TA:  Jpn J Pharmacol     Country:  JAPAN    
Other Details:
Languages:  eng     Pagination:  357-62     Citation Subset:  IM    
Affiliation:
Department of Toxicology and Pharmacology, Faculty of Pharmaceutical Sciences, University of Tokyo, Japan.
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MeSH Terms
Descriptor/Qualifier:
Adrenergic alpha-Antagonists / pharmacology
Animals
Blood Pressure / drug effects
Clonidine / analogs & derivatives*,  antagonists & inhibitors,  pharmacology
Decerebrate State / physiopathology
Dioxanes / pharmacology
Hexamethonium Compounds / pharmacology
Idazoxan
Male
Muscle Relaxants, Central / antagonists & inhibitors,  pharmacology*
Norepinephrine / physiology*
Phentolamine / pharmacology
Prazosin / pharmacology
Rats
Rats, Wistar
Receptors, Adrenergic, alpha-1 / antagonists & inhibitors,  drug effects
Receptors, Adrenergic, alpha-2 / antagonists & inhibitors,  drug effects
Reflex / drug effects*
Reflex, Monosynaptic / drug effects
Spinal Cord / physiology*
Sympathetic Nervous System / drug effects,  physiology*
Chemical
Reg. No./Substance:
0/Adrenergic alpha-Antagonists; 0/Dioxanes; 0/Hexamethonium Compounds; 0/Muscle Relaxants, Central; 0/Receptors, Adrenergic, alpha-1; 0/Receptors, Adrenergic, alpha-2; 19216-56-9/Prazosin; 4205-90-7/Clonidine; 50-60-2/Phentolamine; 51-41-2/Norepinephrine; 51322-75-9/tizanidine; 79944-58-4/Idazoxan

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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