Levetiracetam Ameliorates L-DOPA-Induced Dyskinesia in Hemiparkinsonian Rats Inducing Critical Molecular Changes in the Striatum

Abstract

L-DOPA-induced dyskinesias (LID) remain a major problem of long-term therapy of Parkinson's disease. Levetiracetam, a new antiepileptic drug, has been shown to reduce LID, but the mechanisms underlying its effects are unknown. In this study, we assessed the effect of levetiracetam on key mediators of LID in rats with 6-hydroxydopamine (6-OHDA) lesions. Following chronic administration of L-DOPA (12 mg/kg, twice daily for 14 days), rats developed abnormal involuntary movements (AIMs), but co-administration of levetiracetam (15, 30, and 60 mg/kg) with equivalent L-DOPA dosing significantly reduced AIMs scores in a dose dependent manner. The effects of levetiracetam were associated with changes in striatal expression of ΔFosB, phosphorylated extracellular signal-regulated kinases 1 and 2 (p-ERK1/2), and phosphorylated cAMP-regulated phosphoprotein of 32 kDa (p-DARPP-32). These data support that levetiracetam acts at multiple sites in the pathogenetic cascade of LID, and that further understanding of these actions of antiepileptics may contribute to developing new LID therapies.

Figure 1

Effects of levetiracetam on abnormal involuntary movements (AIMs) induced by L-DOPA in hemiparkinsonian rats. Animals were assessed on days 1, 3, 5, 7, 9, 11, and 14 following L-DOPA methyl ester (12 mg/kg) plus benserazide-HCl (3 mg/kg) (i.p.). Two hours prior to each L-DOPA injection, animals received levetiracetam 0 (control group, vehicle injection), 15, 30, or 60 mg/kg by gavage. Total AIMs scores (a) include orofacial (b), axial (c), and limb (d) AIMs scores. Rotational behavior (contralateral turns, (e)) shows that levetiracetam induced no changes in the antiparkinsonian action of L-Dopa. Values are mean ± SEM. ^* P < 0.05 and ^** P < 0.01 versus control group (n = 10 per group; LEV: levetiracetam).

Figure 2

Levetiracetam-induced changes in FosB/ΔFosB immunostaining of the dorsolateral portion of the striatum. (a) Images of striatal slices from the lesion side of an animal from each treatment group (control, 15, 30, and 60 mg/kg levetiracetam denoted as LEV; ×200). (b) Immunoreactive cell count in each treatment group. Values are mean ± SEM. ^* P < 0.05 and ^** P < 0.01 versus control group (n = 4 per group).

Figure 3

Levetiracetam-induced expression changes of the ΔFosB and phosphorylation of ERK1/2 in the dorsolateral portion of the striatum. Images display immunoblots from striatal tissue (IL: ipsilateral side; CL: contralateral side) from one animal in each levetiracetam treatment group, and immunoblots correspond to FosB, ΔFosB, and β-actin as internal control. Levetiracetam 60 mg/kg significantly reduced the striatal ΔFosB expression (a). ^# P < 0.05 versus same side of control group (n = 6 per group; LEV: levetiracetam). Images display immunoblots from striatal tissue (IL: ipsilateral side; CL: contralateral side) from one animal in each levetiracetam treatment group, and immunoblots correspond to p-ERK1/2 and β-actin as internal control. Levetiracetam 30 and 60 mg/kg significantly reduced the striatal p-ERK1/2 expression (b). ^* P < 0.05 and ^** P < 0.01 versus same side of the control group (n = 6 per group; LEV: levetiracetam).

Figure 4

Levetiracetam-induced changes in the phosphorylation of DARPP-32 in the dorsolateral portion of the striatum. (a) Images display immunoblots from striatal tissue (lesioned and unlesioned side) from one animal in each levetiracetam treatment group. Immunoblots correspond to p-DARPP-32 and β-actin as internal control. The graph compares p-DARPP-32 expression across treatment groups. Levetiracetam 60 mg/kg significantly reduced the striatal p-DARPP-32 expression. ^** P < 0.01 versus same side of the control group. (b) Images display immunoblots from striatal tissue (IL: ipsilateral side; CL: contralateral side) from one animal in each levetiracetam treatment group. Immunoblots correspond to total DARPP-32 and β-actin as internal control. The graph compares total DARPP-32 expression across treatment groups. Levetiracetam had nonsignificant effects on the striatal total DARPP-32 expression (n = 6 per group; LEV: levetiracetam).