Proceedings of The Physiological Society

Physiology 2014 (London, UK) (2014) Proc Physiol Soc 31, C14

Oral Communications

L-DOPA induced dyskinesia is associated with neuroinflammation in an 6-OHDA rat model

M. Bortolanza1,2, R. Cavalcanti-Kiwiatkoski1, F. E. Padovan-Neto3,2, C. A. da-Silva1,2, R. Raisman-Vozari4, E. Del Bel1,2

1. Morphology, Physiology and Basic Patology, University of Sao Paulo- Ribeirao Preto Dental School, Ribeirao Preto, Sao Paulo, Brazil. 2. Center for Interdisciplinary Research on Applied Neurosciences (NAPNA), University of Sao Paulo- Ribeirao Preto Dental School, Sao Paulo, Sao Paulo, Brazil. 3. Neurologia-Neurociencias, Universidade de sao Paulo- Faculdade de medicina de Ribeirao Preto, Ribeirao Preto, Sao Paulo, Brazil. 4. Institut de Cerveau et de la Moelle Epini

Dyskinesia produced by long-term treatment with levodopa in the Parkinson disease patient remains a serious clinical problem. Rodent preparation have been developed to allow studies into possible causative mechanism. One experimental preparation is the microinjection of the neurotoxin 6-OHDA into medial forebrain bundle (MFB), followed by a treatment during three weeks with levodopa (30mg/kg+benserazide7.5mg/kg/21days). Nitric oxide synthase (NOS) inhibitor abolishes levodopa-induced dyskinesia (LID). Although the development of LID depends on the dopaminergic neuron lesion it is not known if a neuroinflamatory reaction is engaged in the development and/or maintenance. Dyskinesia model: Wistar rats (male, 180-200g, n=23) anesthetized with a mixture of Ketamine (80mg/kg) xylazine (10mg/kg), i.p., were submitted to a stereotaxic surgery (Padovan-Neto et al., 2009) receiving a single injection of 6-OHDA (24µg/3µl/0.05% ascorbic acid-right MFB). Desipramine hydrochloride (25 mg/kg i.p), pargyline (40 mg/kg) were administered 30 min before 6-OHDA. The development of LIDS was documented using a scale (Padovan-Neto et al., 2009). After three weeks, rats were divided into four sub-groups, daily treated with L-DOPA (30mg/kg) or saline for 21 days preceded by 7-NI (30mg/kg) or vehicle (saline-DMSO 50%). Three hours after the last drug administration, rats were anesthetized (urethane25 mg/kg), perfused (saline 250ml + heparin (25000 IU/mL+ sodium nitrite (1g/L solution), followed by 300ml of PFA 4%, 0.1 M PBS. Brains were post-fixed (2 hours, 4°C), cryoprotected (sucrose 30%, pH 7.4, 4 °C, 48 hours) frozen and processed by histology. Neuroinflamatory reaction was monitored by immunohistochemistry in the striatum of the inducible NOS (iNOS), of the glial fibrillary acidic protein (GFAP-astrocytes), of the anti-CD11b antibody/equivalent protein (clone OX-42-microglia). Images were digitized with a video-camera (Leica DFC420), evaluated with the Image J ( Behavioural values are presented as means±S.E.M., compared by Mann-Whitney U test and r-MANOVA, respectively. Rats developed abnormal involuntary movements (AIMS) (axial, limb and orofacial=20.85±1.28; locomotor=3.78±0.76) wiche were reduced by NOS-inhibitor (p<0.05). There was in the dopamine depleted lateral striatum an increase in the expression of the iNOS (48.29± 0.56), of the GFAP/astrocytes (12850 ± 189.3) and of the OX-42/microglia (8671±250.4), decreased by 7-NI (iNOS=30.86±0.59; GFAP=6624 ± 172.5; OX-42=3775±126.9). Thus, this established model of experimental diskinesia is associated with components of inflammatory cascade. These data suggest that levodopa (chronically) to parkinsonian rats may cause AIMS via mechanisms involving neuroinflamation.

Where applicable, experiments conform with Society ethical requirements