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Neurosci Lett. 1989 Feb 13;97(1-2):221-6.

Myorelaxant effect after intrathecal injection of antispastic drugs in rats.

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Max-Planck-Institute for Experimental Medicine, Göttingen, F.R.G.


The effects of intrathecal ( injections of antispastic drugs were studied on spontaneous activity in the electromyogram (EMG) in genetically spastic rats and on spinal reflex transmission in anaesthetized normal rats. Baclofen, 0.2-2 nmol, and midazolam, 10-80 nmol, suppressed tonic activity in the EMG recorded from the gastrocnemius muscle in mutant rats, whereas tizanidine, 1-100 nmol, enhanced it. The action of baclofen was antagonized by co-administration of delta-aminovalerate but not by bicuculline, that of midazolam by systemic pretreatment with Ro 15-1788. The effect of tizanidine was antagonized by co-administration of prazosin but not by yohimbine. Baclofen, 2 nmol, exerted suppressant effects on Hoffman (H)-reflexes and spinal flexor reflexes in normal animals, midazolam, 80 nmol, only on flexor reflexes. Tizanidine, 100 nmol, failed to suppress H-reflexes and flexor reflexes. The present results demonstrate a myorelaxant effect of injections of baclofen and midazolam but not of tizanidine.

[Indexed for MEDLINE]

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