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  • Title: Metabotropic glutamate receptor II in the brains of Parkinsonian patients.
    Author: Samadi P, Rajput A, Calon F, Grégoire L, Hornykiewicz O, Rajput AH, Di Paolo T.
    Journal: J Neuropathol Exp Neurol; 2009 Apr; 68(4):374-82. PubMed ID: 19287314.
    Abstract:
    Modulation of basal ganglia group II metabotropic glutamate receptors (mGluR2/3) is a potential therapeutic alternative to levodopa in Parkinson disease (PD). We used receptor-binding autoradiography of the mGluR2/3-selective radioligand [H]LY341495 in postmortem brain specimens from PD patients (n = 14) and controls (n=11) to investigate possible contributions of changes in ligand binding of this receptor to levodopa-associated motor complications experienced premortem in PD patients. The PD patients included those with and without histories of dyskinesias and those with and without "wearing off," which is defined as a reduced period of benefit from levodopa. Specific binding of [H]LY341495 to mGluR2/3 in the basal ganglia was higher in the caudate nucleus than the putamen and lower by approximately half in the external and internal globus pallidus (GPi) in controls. [H]LY341495-specific binding was reduced in the caudate and GPi in patients without wearing-off (-22% caudate, -30% GPi), compared with controls and with patients who had experienced wearing-off; there were no differences among PD patients with or without dyskinesias. These data suggest that an adaptive downregulation of mGluR2/3 in PD patients without wearing-off may compensate for increased glutamate. They indicate a key role for mGluR2/3 in control of movement and the potential for mGluR2/3-targeted drugs in the management of wearing-off fluctuations in PD.
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