title: Substantia nigra and entopeduncular nucleus: supraspinal sites of the muscle relaxant action of tizanidine.
abstract: 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.
mesh_terms: 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
chemical_list: D009125:Muscle Relaxants, Central; D015016:Yohimbine; C023754:tizanidine; D003000:Clonidine