Role of GABAergic mechanisms in the substantia nigra pars reticulata in modulating morphine-induced muscular rigidity in rats.
Systemic administration of morphine (15 mg/kg i.p.) induced a muscular rigidity in rats, which was recorded from the gastrocnemius-soleus muscle as tonic activity in the electromyogram (EMG). Administration of muscimol (12.5 or 25 ng) into the substantia nigra pars reticulata (SNR) antagonized the rigidity in a dose-dependent manner, whereas bicuculline enhanced it. It was concluded that GABAergic mechanisms in the SNR play an important role in mediating or modulating the expression of the morphine-induced rigidity, which is known to be due to an alteration of striatal function via opioid receptors located in this brain area.
D000818:Animals; D001640:Bicuculline / Q000494:pharmacology; D002421:Caudate Nucleus / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004576:Electromyography; D006614:Hindlimb; D008297:Male; D009020:Morphine / Q000494:pharmacology*; D009118:Muscimol / Q000494:pharmacology; D009129:Muscle Tonus / Q000187:drug effects*; D009434:Neural Pathways / Q000187:drug effects; D051381:Rats; D011919:Rats, Inbred Strains; D011956:Receptors, Cell Surface / Q000187:drug effects*; D011963:Receptors, GABA-A; D013378:Substantia Nigra / Q000187:drug effects*; D009435:Synaptic Transmission / Q000187:drug effects
D011956:Receptors, Cell Surface; D011963:Receptors, GABA-A; D009118:Muscimol; D009020:Morphine; D001640:Bicuculline