Movement disorders induced by gamma-aminobutyric agonist and antagonist injections into the internal globus pallidus and substantia nigra pars reticulata of the monkey

Effects of Transient Focal Inactivation of the Basal Ganglia in Parkinsonian Primates

“…1 B). Wurtz, 1983a-c;Burbaud et al, 1998;Lestienne and Thullier, 1998;Wichmann et al, 2001). In the present experiments, contraversive circling, as well as truncal and head turning, gaze deviation, and horizontal nystagmus, were induced by muscimol injections placed into the rostral "associative" portions of GPi and STN and could be readily dissociated from sites producing anti-akinetic and anti-bradykinetic effects.…”

GABAergic output of the basal ganglia

“…If the GABAergic output is reduced by injecting muscimol (GABA A agonist) in the SNr of MPTPinduced parkinsonian monkeys, their body movements are improved (Wichmann et al, 2001). In normal monkeys injections of muscimol (GABA agonist) in the GP i , which should reduce the GABA output, induces choreiform movements, while injections of bicuculline (GABA A antagonist) in the GP i , which should block incoming GABA-induced inhibitions, induced hypokinesia (Burbaud et al, 1998). Bergmann and colleagues have also shown that the GABAergic output is not stable but fluctuates in an oscillatory manner in MPTP-induced parkinsonian monkeys, but not in control monkeys (Bar-Gad et al, 2004).…”

“…On the other hand, patients with basal ganglia dysfunction commonly have difficulty in initiating purposeful movements (akinesia) and, if initiated, the movements tend to be slow and small (hypokinesia). This type of movement disorder could be caused by an insufficient removal (or disinhibition) of the SNr/GP i -induced inhibition (Burbaud et al, 1998).…”

Dystonia Pathophysiology: A Critical Review

“…However, when lower volumes (2l) are used, abnormal focal postures in the lower limbs close to off-dystonia are observed (39). Severe hypertonic postures in controlateral limbs are noticed after GPi injections whereas SNr injections generally induce more axial symptoms, particularly in the neck.…”

“…Bic injection into the STN blocks GABAergic inputs, increases activity and leads to a tonic dystonia (42). Conversely, the injection of muscimol, a GABAergic agonist, within the basal ganglia output structures, namely the internal pallidum (GPi), and pars reticulata of the substantia nigra (SNr) induces a mobile dyskinesias encompassing mixed choreic and dystonic features mimicking the hyperkinetic movements observed in idiopathic dystonias (39). The mechanism could be related to an inhibition of neuronal activity in these regions (47).…”