Effect of adenosine A2A receptor antagonists on motor disorders induced by 6-hydroxydopamine in rat

PURPOSE: To investigate the role of adenosine A2A receptors on 6-OHDA-induced motor disorder in rat. METHODS: In order to induce experimental model of Parkinson's disease, 6-hydoxydopamine (8 μg/rat) was injected unilaterally into the SNc. After three weeks as a recovery period, 6-OHDA-induced bradykinesia and balance disturbances were assessed by using beam traversal test 10, 30 and 60 minutes after intraperitoneal injections of the drugs (caffeine, SCH58261). RESULTS: The results showed that 6-OHDA (8 μg/rat, Intra-SNc) induced motor disorders of Parkinson's disease and increased elapsed time in the beam test (p<0.001). Injection of caffeine (30 mg/kg, i.p.) and SCH58261 (2 mg/kg, i.p.) attenuated elapsed time on beam (p<0.01 and p<0.001). We showed that acute administration of caffeine and SCH 58261 can improve the 6-OHDA-induced bradykinesia and motor disturbance. CONCLUSION: Adenosine A2AR antagonists improve 6-OHDA-motor deficit and this effect seems to be mediated by the inhibition of A2A presynaptic receptors in substantia nigra pars compacta.

Effect of High-Frequency Stimulation in the Pedunculopontine Nucleus on Neuronal Activity and Neurotransmitters in the Globus Pallidus Internus of Rats / 天津医药

Objective To study the effect of high frequency stimulation (HFS) in pedunculopontine nucleus (PPN) on the neuronal activities of globus pallidus internus (Gpi) in Parkinson’s disease (PD) model rats, and the mechanisms there-of. Methods Seventy male Sprague-Dawley rats were divided into two groups, control group (n=30) and PD model group (n=40). PD rat model was established by the injection of 6-OHDA into substantia nigra pars compacta (SNc) on the right side of the brain with stereotactic technique. Electrophysiological recordings were made in anaesthetized rats to investigate the ef-fects of HFS-PPN on the firing rate of the GPi neurons. Brain microdialysis combined with high-performance liquid chroma-tography was applied to detect glutamate (Glu) andγ-aminobutyric acid (GABA) levels in GPi. Results HFS-PPN caused an excitatory reaction of the majority of neurons recorded in the GPi in PD model group and control group. The mean firing rate of GPi excited neurons was significantly increased (P﹤0.01). The levels of Glu were reduced under HFS-PPN and the levels of GABA were not affected (P>0.05).Conclusion HFS-PPN heightened the electrical activity of GPi neurons and re-duced the level of Glu. These excitatory effects were probably realized by PPN-GPi direct path or other indirect path.

Effects of 6-hydroxydopamine and inhibitors for vesicular monoamine transporter on monoamine neurotransmitter and rate-limiting enzyme gene of them in PC12 cells / 中华神经科杂志

ObjectiveTo study the effects of 6-hydroxydopamine (6-OHDA),and inhibitors for vesicular monoamine transporter (VMAT) on 5-hydroxytryptamine (5-HT),norepinephrine (NE) and dopamine (DA) and the expressions of tryptophan hydroxylase (TpH) mRNA,dopamine-beta-hydroxylase (DβH) mRNA and tyrosine hydroxylase (TH) mRNA in PC12 cells.Methods The cell viability was determined using MTT assay, the density of 5-HT, NE and DA was detected using enzyme-linked immunosorbent assay,and the expressions of TpHmRNA,DβHmRNA and THmRNA were detected using RT-PCR in PC12 cells at different time points (0,12,24,36,48 h )after exposure to different concentrations of 6-OHDA(25,50,100,200 μmol/L),and VMAT inhibitors,reserpine (50,100,400,1600 nmol/L),which combined with 6-OHDA( 100 μmol/L).Results (1)The cell viability declined with the increasing concentration of 6-OHDA which showed time dependence.The cell viability in PC12 cell which treated with reserpine decreased significantly in the responding group.The density of 5-HT in PC12 cell did not decrease with the increasing concentration of 6-OHDA,but the change had the time dependence,and the density of 5-HT was lowest at 36 h.The density of NE decreased with the increasing concentration of 6-OHDA which showed time dependence. The density of DA in PC12 cell decreased with the increasing concentration of 6-OHDA,but the change did not have the time dependence.The density of 5-HT,NE and DA in PC12 cell which treated with reserpine decreased significantly in the responding group. (2) The expressions of TpHmRNA, DβHmRNA and THmRNA in PC12 cell decreased with the increasing concentration of 6-OHDA which showed time dependence.The expressions of TpHmRNA(0.006 ± 0.001,0.003 ± 0.000,0.003 ± 0.000,0.002 ± 0.000) ; DβHmRNA (0.005 ± 0.002,0.003 ± 0.001,0.002 ±0.001,0.001 ± 0.000) and THm RNA (0.005 ± 0.002,0.003 ± 0.001,0.002 ± 0.001,0.001 ± 0.000) in PC12 cell which treated with reserpine decreased significantly in the responding group(F =13.336,9.000,9.393,all P =0.000).Conclusions6-OHDA can decrease the cell viability in PC12 cell,reduce the density of 5-HT,NE and DA and decrease the expressions of TpHmRNA,DβHmRNA and THmRNA,and the effects have dose and time dependence.Reserpine can aggravate this damage.

Protective effects of fustin, a flavonoid from Rhus verniciflua tokes, on 6-hydroxydopamine-induced neuronal cell death

6-Hydroxydopamine (6-OHDA) is a neurotoxin and is commonly used to generate experimental models of Parkinson's disease (PD). In this study, we investigated the signaling molecules involved in the 6-OHDA-induced cell death using a neuronal catecholaminergic cell line (SK-N-SH cells), and the protective effect of fustin, a flavonoid from Rhus verniciflua Stokes, on 6-OHDA-induced neuronal death. 6-OHDA significantly increased levels of reactive oxygen species (ROS), intracellular Ca2+ ([Ca2+](i)), and p38 phosphorylation. In addition, this ROS increase by 6-OHDA was reduced by pretreatment with N-acetylcysteine (NAC), a free radical scavenger, but not by bis-(o-aminophenoxy)-ethane-N,N,N,N-tetraacetic acid (BAPTA), a Ca2+ chelator. However, the [Ca2+](i) increase induced by 6-OHDA was suppressed by NAC. Moreover, pretreatment with NAC or BAPTA significantly prevented the 6-OHDA-induced increases in p38 phosphorylation, Bax/Bcl-2 ratio, and caspase-3 activity. Although 6-OHDA-increased phosphorylation of p38 was prevented by NAC or BAPTA, inhibition of p38 by SB203580 did not suppress ROS, Bax/Bcl-2 ratio, or caspase-3 activity increases, and only partially prevented 6-OHDA-induced cell death, thus demonstrating that p38 activation is a component of a signaling pathway leading to the initiation of 6-OHDA-induced cell death, which acts in parallel with an ROS-Ca2+ -Bcl-2-caspase-3 pathway. Moreover, fustin not only suppressed 6-OHDA-induced cell death in a concentration-dependent manner but also blocked 6-OHDA-induced increases in ROS, [Ca2+](i), Bax/Bcl-2 ratio, caspase-3 activity, and p38 phosphorylation. These results suggest that fustin exerts neuroprotection against 6-OHDA-induced cell death.

CHANGES OF DOPAMINE RECEPTOR ACTIVITY IN CAUDALPUTAMEN OF PARKINSON DISEASE RAT MODEL / 解放军医学杂志

To explore the role and changes of dopamine receptor activity and their subtypes during the onset process of Parkinson disease( PD ), on the basis of 6 hydroxydopamine lesioned PD rat model, radioligand binding assay (RLBA) and Scanchard drawing were used to measure the maximal binding capacity of receptor (Bmax) and equilibrium dissociation constant (KD) of D 1 and D 2 dopamine receptors in caudal putamen of the model and control rats at different time point. The results of RLBA study revealed D 2 dopamine receptor Bmax was significantly increased and KD was significantly decreased in the caudal putamen ipsilateral to the lesion in rat model, and the changes reached the peak in one month rat model group. In contrast, the caudal putamen D 1 receptors were far less affected, with no consistent changes in the same model groups as compared with the control, except that 2 weeks model group showed Bmax was slightly decreased while KD was slightly increased. The study confirms that D 2 dopamine receptor is upregulated in the caudal putamen ipsilateral to the lesion in PD rat model, and the affinity of the receptors is increased, but the activity of D 1 dopamine receptor is not significantly changed.