Effect of the metabotropic glutamate antagonist MPEP on striatal expression of the Homer family proteins in levodopa-treated hemiparkinsonian rats.
BACKGROUND
Striatal glutamatergic hyperactivity through the metabotropic receptors and their intracellular signaling pathways is considered critical in the development of levodopa-induced dyskinesias in Parkinson's disease and in experimental parkinsonism.


OBJECTIVE
We investigated whether the administration of the metabotropic glutamate antagonist, MPEP, modifies striatal expression of Homer family proteins which are involved in the intracellular mechanisms mediated by these receptors.


METHODS
Sprague-Dawley rats were unilaterally lesioned in the nigrostriatal pathway with 6-hydroxydopamine (8 microg) and treated with: levodopa (12 mg/kg, i.p.) plus vehicle (n=10) divided in two daily injections; levodopa plus MPEP (1.5 and 3 mg/kg, i.p.; n=6-13) divided in two daily injections; or saline (n=7) for 10 consecutive days. Axial, limb, and orolingual dyskinesias were evaluated. Striatal expression of tyrosine hydroxylase (TH), Homer 1a, 1b/c, and deltaFosB were measured by Western Blot.


RESULTS
Animals treated with levodopa showed an increase of dyskinesia score (p<0.01) that was attenuated by the administration of MPEP (p<0.01). In the ipsilateral side of the lesion, striatal TH expression was decreased (p<0.01). No significant differences in striatal Homer 1a or b/c expression were observed between the groups of treatment. Striatal deltaFosB expression increased in the animals treated with levodopa (p<0.05) being attenuated after MPEP administration (p<0.05). MPEP effect was not paralleled by any modification of striatal Homer proteins expression.


CONCLUSIONS
These results suggest that Homer protein family is not causally involved in the development of dyskinetic movements induced by levodopa treatment in this animal model of parkinsonism.
Jiménez
Anna
A
Laboratori de Neurologia Experimental, Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Spain.
Bonastre
Merce
M
Aguilar
Esther
E
Marin
Concepcio
C
D000818:Animals; D000978:Antiparkinson Agents / Q000009:adverse effects / Q000627:therapeutic use; D002352:Carrier Proteins / Q000378:metabolism*; D003342:Corpus Striatum / Q000187:drug effects* / Q000378:metabolism; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D004409:Dyskinesia, Drug-Induced / Q000209:etiology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology*; D005786:Gene Expression Regulation / Q000187:drug effects*; D000072233:Homer Scaffolding Proteins; D007980:Levodopa / Q000009:adverse effects / Q000627:therapeutic use; D008297:Male; D016627:Oxidopamine; D020734:Parkinsonian Disorders / Q000139:chemically induced / Q000188:drug therapy / Q000473:pathology*; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism; D011725:Pyridines / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D014446:Tyrosine 3-Monooxygenase / Q000378:metabolism
D000978:Antiparkinson Agents; D002352:Carrier Proteins; D018691:Excitatory Amino Acid Antagonists; D000072233:Homer Scaffolding Proteins; D016760:Proto-Oncogene Proteins c-fos; D011725:Pyridines; D007980:Levodopa; C121465:6-methyl-2-(phenylethynyl)pyridine; D016627:Oxidopamine; D014446:Tyrosine 3-Monooxygenase