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BACKGROUND: Radio-imaging has been used in neurological diagnosis,in particular for extrapyramidal disease.Moreover,it has been extensively utilized for early diagnosis of Parkinson’s disease (PD) patients and in animal studies.However,it has rarely been utilized to assess drug-induced side effects in PD.OBJECTIVE: To investigate changes in dopamine transporter expression in a rat model of PD through the use of radio-imaging taking 99mTc-TRODAT-1 as an imaging agent,and to explore the effect of levodopa (L-dopa) on dopaminergic neurons and the possible mechanisms of dyskinesia induction.DESIGN,TIME AND SETTING: A randomized,controlled,animal study was performed at the Laboratory of Department of Nuclear Medicine,Soochow University from April 2006 to June 2007.MATERIALS: 6-hydroxydopamine was purchased from Sigma,USA and L-dopa was purchased from Shanghai Fuda Pharmaceutical,China.99mTcO4-fresh elutriant was provided by the Department of Nuclear Medicine,First Hospital Affiliated to Soochow University.TRODAT-1 image kit was provided by Jiangsu Atomic Energy Research Establishment,China.The SN-695B radioimmunoassay gamma counter was purchased from Shanghai Hesuo Rihuan Photoelectric Instrument,China.The AZ-CA256eZ-Scope portable γ camera was purchased from Anzai Medical,Japan.METHODS: A total of 34 healthy,male,Sprague Dawley rats were selected.Thirty were used to establish a PD model by injecting 6-hydroxydopamine into the right medial forebrain bundle,and four were injected with normal saline and served as the sham-surgery group.At the end of 4 weeks,21 successful PD models were selected and randomly assigned to the L-dopa (n = 15,20 mg/kg per day),model (n = 6,normal saline),and sham-surgery (n = 4,no treatment) groups.After 1 month of treatment,involuntary movement was evaluated twice weekly in each rat.A total of 0.2 mL 99mTc-TRODAT-1 was injected into the tail vein 2 days following drug termination,and images of dopamine transporters were acquired 2 hours later.The rats were sacrificed and the ratios of specific radioactivity uptake were calculated.MAIN OUTCOME MEASURES: Manifestations of abnormal involuntary movement (AIM) were observed and total AIM scores were calculated.Images of dopamine transporters were acquired using an eZ-Scope portable γ camera,and radioactive γ quantification of 99mTc-TRODAT-1 in the rat brains was assayed.The ratios of the left and right corpora striata were determined.The number and function of dopamine transporters was evaluated according to specific radioactivity uptake ratio (R) from the left and right corpora striata.RESULTS: Of 15 PD rats,nine exhibited AIM following L-dopa treatment: five scored > 20,i.e.,severe grade,four scored 8–16,mild grade,and the remaining exhibited normal behavior.There were no differences in specific radioactivity uptake of dopamine transporter between the left and right corpora striata in the sham-surgery rats,and the images were clear and symmetrically distributed.Specific radioactivity uptake of the normal side (left) was significantly greater than the lesioned side (right) in the model group rats (P < 0.01),and the R value was significantly increased compared with the sham-surgery group (P < 0.01).The radio-ligand accumulation in the right corpus striatum was sparse.In the L-dopa group,specific radioactivity uptake was significantly decreased in the lesioned (right) side of the AIM rats,and the R value was increased compared with the model group (P < 0.05).The amount of radio-ligand in the right corpus striatum was diminished.The R value was significantly reduced in the non-AIM rats compared with the AIM rats (P < 0.05),and specific radioactivity uptake was significantly increased in the lesioned (right) side compared with the normal side (P < 0.05).Moreover,radio-ligand accumulation was observed in the right corpus striatum,and differences in radio-ligand accumulation between the two sides were reduced.CONCLUSION: Following L-dopa treatment,the number and function of dopamine transporter in some PD rats were reduced.L-dopa was shown to be toxic to dopaminergic neurons and induced dyskinesia.
BACKGROUND: Radio-imaging has been used in neurological diagnosis, in particular for extrapyramidal disease. Moreover, it has been extensively utilized for early diagnosis of Parkinson’s disease (PD) patients and in animal studies. However, it has been been been to assess drug -induced side effects in PD. OBJECTIVE: To investigate changes in dopamine transporter expression in a rat model of PD through the use of radio-imaging taking 99mTc-TRODAT-1 as an imaging agent, and to explore the effect of levodopa (L- dopa) on dopaminergic neurons and the possible mechanisms of dyskinesia induction. DESIGN, TIME AND SETTING: A randomized, controlled, animal study was performed at the Laboratory of Department of Nuclear Medicine, Soochow University from April 2006 to June 2007. SPECIALS: 6- hydroxydopamine was purchased from Sigma, USA and L-dopa was purchased from Shanghai Fuda Pharmaceutical, China.99mTcO4-fresh elutriant was provided by the Department of Nuclear Medicine, First Hospital Affiliated to S oochow University.TRODAT-1 image kit was provided by Jiangsu Atomic Energy Research Establishment, China. The SN-695B radioimmunoassay gamma counter was purchased from Shanghai Hesuo Rihuan Photoelectric Instrument, China. The AZ-CA256eZ-Scope portable gamma camera was purchased from Anzai Medical, Japan. METHODS: A total of 34 healthy, male, Sprague Dawley rats were selected. Thirty were used to establish a PD model by injecting 6-hydroxydopamine into the right medial forebrain bundle, and four were injected with normal saline and served as the sham-surgery group. At the end of 4 weeks, 21 successful PD models were selected and randomly assigned to the L-dopa (n = 15, 20 mg / kg per day), model and sham-surgery (n = 4, no treatment) groups. After 1 month of treatment, involuntary movement was evaluated twice weekly in each rat. A total of 0.2 mL 99mTc-TRODAT-1 was injected into the tail vein for 2 days following drug termination, and images of dopamine transporters were acquired 2 hours lat er.The rats were sacrificed and the ratios of specific radioactivity uptake were taken. MAIN OUTCOME MEASURES: Manifestations of abnormal involuntary movement (AIM) were observed and total AIM scores were calculated .Images of dopamine transporters were acquired using an eZ-Scope portable γ camera, and radioactive γ quantification of 99mTc-TRODAT-1 in the rat brains was assayed. The ratios of the left and right corpora striata were determined. The number and function of dopamine transporters were evaluated according to the specific radioactivity uptake ratio (R) from the left and right corpora striata.RESULTS: Of 15 PD rats, nine exhibited AIM following L-dopa treatment: five scored> 20, ie, severe grade, four scored 8-16, mild grade, and the remaining demonstrated normal behavior.There were no differences in specific radioactivity uptake of dopamine transporter between the left and right corpora striata in the sham-surgery rats, and the images were clear and symmetrically distributed.Specific ra dioactivity uptake of the normal side (left) was significantly greater than the lesioned side (right) in the model group rats (P <0.01), and the R value was significantly increased compared to the sham-surgery group (P <0.01). The radio-ligand accumulation in the right corpus striatum was sparse.In the L-dopa group, specific radioactivity uptake was significantly decreased in the lesioned (right) side of the AIM rats, and the R value was increased compared with the model group ( The amount of radio-ligand in the right corpus striatum was diminished. The R value was significantly reduced in the non-AIM rats compared with the AIM rats (P <0.05), and the specific radioactivity uptake was significantly increased in The lesioned (right) side compared with the normal side (P <0.05). Moreover, radio-ligand accumulation was observed in the right corpus striatum, and differences in radio-ligand accumulation between the two sides were reduced. CONCLUSION: Following L- dopa treatment, the number a nd ffunction of dopamine transporter in some PD rats were reduced. L-dopa was shown to be toxic to dopaminergic neurons and induced dyskinesia.