Spinal α1- and α2-Adrenoceptors Mediate Facilitation and Inhibition of Spinal Motor Transmission, Respectively
Open Access
- 1 January 1990
- journal article
- research article
- Published by Elsevier in The Japanese Journal of Pharmacology
- Vol. 54 (1), 69-77
- https://doi.org/10.1254/jjp.54.69
Abstract
The role of descending noradrenergic fibers in the spinal motor systems was investigated using spinal reflexes in acutely spinalized rats. In rats pretreated with the MAO inhibitor clorgyline-HCl (1 mg/kg, i.v.), L-3,4-dihydroxyphenylalanine (L-dopa) (5 mg/kg, i.v.), a precursor of dopamine and noradrenaline, markedly potentiated the mono- (MSR) and polysynaptic reflexes (PSR). Selective blockade of .alpha.1-adrenoceptors by pretreatment with prazosin-HCl abolished these facilitatory effects on the MSR and the PSR and revealed the inhibitory effect of L-dopa on the PSR. The depression of PSR was antagonized by the .alpha.2-antagonist piperoxan. Clonidine-HCl (0.05 mg/kg, i.v.), a so-called .alpha.2-agonist, and tizanidine-HCl (0.1 mg/kg, i.v.) decreased the MSR and the PSR in rats pretreated with prazosin. These inhibitions were antagonized by piperoxan. These results suggest that .alpha.1- and .alpha.2-adrenoceptors mediate facilitation and attenuation of motor transmission in the rat spinal cord, respectively.This publication has 26 references indexed in Scilit:
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