Spinal α1- and α2-Adrenoceptors Mediate Facilitation and Inhibition of Spinal Motor Transmission, Respectively

[摘要] References(29)Cited-By(19)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 α1-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 α2-antagonist piperoxan. Clonidine-HCl (0.05 mg/kg, i.v.), a so-called α2-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 α1- and α2-adrenoceptors mediate facilitation and attenuation of motor transmission in the rat spinal cord, respectively.

[学科分类] 药理学