Substantia nigra and entopeduncular nucleus: supraspinal sites of the muscle relaxant action of tizanidine.
Microinjection of tizanidine into the substantia nigra pars reticulata or entopeduncular nucleus reduces muscle tone in genetically spastic rats. The effect of tizanidine is related to alpha 2-adrenergic mechanism since yohimbine, an alpha 2-adrenergic antagonist, and not prazosin, an alpha 1-adrenergic antagonist, attenuates the muscle relaxation produced by the drug. These results signify basal ganglia output stations as possible sites whereby tizanidine acting via alpha 2-adrenergic mechanism exerts its muscle relaxant action.
D000818:Animals; D001479:Basal Ganglia / Q000187:drug effects*; D003000:Clonidine / Q000031:analogs & derivatives* / Q000494:pharmacology; D004576:Electromyography; D009125:Muscle Relaxants, Central / Q000494:pharmacology*; D009129:Muscle Tonus / Q000187:drug effects; D051381:Rats; D011919:Rats, Inbred Strains; D013378:Substantia Nigra / Q000187:drug effects*; D015016:Yohimbine / Q000494:pharmacology
D009125:Muscle Relaxants, Central; D015016:Yohimbine; C023754:tizanidine; D003000:Clonidine