6-Hydroxydopamine

Neuroinflammation may play as an important risk factor in progressive degeneration of dopaminergic cells. Antioxidants have protective effects against free radicals-induced neural damage in Parkinson's disease (PD). In the present study, we examined the effects of ellagic acid (EA) on locomotion and neuroinflammatory biomarkers in a rat model of PD induced by 6-hydroxidopamine (6-OHDA). 6-OHDA (16 μg/2 μl) was injected into the right medial forebrain bundle (MFB) in MFB-lesioned rat's brain. Sham group received vehicle instead of 6-OHDA. PD-model was confirmed by rotational test using apomorphine injection. EA (50 mg/kg/2 ml, by gavages) was administered in PD+EA group. One group of MFB-lesioned rats received pramipexole (PPX; 2 mg/kg/2 ml, by gavages) as positive control group (PD+PPX group). Motor activity was assessed by stride length and cylinder tests. The levels of TNF-α and IL-1β were measured in both striatum and hippocampus tissues. MFB lesion caused significant red...

The 6-hydroxydopamine (6-OHDA) lesion is the most widely used rat model of Parkinson's disease. A single unilateral injection of 6-OHDA into the median forebrain bundle (MFB) selectively destroys dopamine neurons in the ipsilateral substantia nigra pars compacta (SNc) and ventral tegmental area (VTA), removing more than 95% of the dopamine innervation from target areas. The stereotaxic coordinates used to deliver 6-OHDA to the MFB have been used in our laboratory successfully for more than 25 years. However, in recent years we have observed a decline in the success rate of this lesion. Previously regular success rates of >80% of rats lesioned, have become progressively more variable, with rates as low as 20% recorded in some experiments. Having excluded variability of the neurotoxin and operator errors, we hypothesized that the change seen might be due to the use of smaller rats at the time of first surgery. An attempt to proportionally adjust the lesion coordinates base on head size did not increase lesion efficacy. However, in support of the small rat hypothesis it was observed that, using the standard coordinates, rat's heads had a "nose-up" position in the stereotaxic fame. Adjustment of the nose bar to obtain a flat head position during surgery improved lesion success, and subsequent adjustments of the lesion coordinates to account for smaller head size led to a greatly increased lesion efficacy (>90%) as assessed by amphetamine induced rotation.

Long-term levodopa (l-dopa) treatment is associated with the development of l-dopa-induced dyskinesias in the majority of patients with Parkinson disease (PD). The etiopathogonesis and mechanisms underlying l-dopa-induced dyskinesias are not well understood. We used striatal optogenetic stimulation to induce dyskinesias in a hemiparkinsonian model of PD in rats. Striatal dopamine depletion was induced unilaterally by 6-hydroxydopamine injection into the medial forebrain bundle. For the optogenetic manipulation, we injected adeno-associated virus particles expressing channelrhodopsin to stimulate striatal medium spiny neurons with a laser source. Simultaneous optical activation of medium spiny neurons of the direct and indirect striatal pathways in the 6-hydroxydopamine lesion but l-dopa naïve rats induced involuntary movements similar to l-dopa-induced dyskinesias, labeled here as optodyskinesias. Noticeably, optodyskinesias were facilitated by l-dopa in animals that did not respond initially to the laser stimulation. In general, optodyskinesias lasted while the laser stimulus was applied, but in some instances remained ongoing for a few seconds after the laser was off. Postmortem tissue analysis revealed increased FosB expression, a molecular marker of l-dopa-induced dyskinesias, primarily in medium spiny neurons of the direct pathway in the dopamine-depleted hemisphere. Selective optogenetic activation of the dorsolateral striatum elicits dyskinesias in the 6-hydroxydopamine rat model of PD. This effect was associated with a preferential activation of the direct striato-nigral pathway. These results potentially open new avenues in the understanding of mechanisms involved in l-dopa-induced dyskinesias. © 2017 International Parkinson and Movement Disorder Society.

Introduction: Studies suggest that ATP-sensitive potassium (KATP) channels are a potential
pharmacotherapeutic target for neuroprotection in neurodegenerative diseases. The current
study aimed at evaluating the effect of pretreatment with glibenclamide (Glib) and B vitamins
supplement on the severity of behavioral symptoms in 6-hydroxydopamine (OHDA)-induced
Parkinsonism. Also malondialdehyde (MDA) concentration was measured in the blood and brain
suspensions to find probable neuroprotective mechanism of Glib.
Methods: The 6-OHDA was injected into striatum of rats by stereotaxic surgery. Treatment
with Glib and B vitamins was started before the surgery and continued up to 3 weeks after that.
Development and severity of Parkinsonism were evaluated by conventional behavioral tests.
MDA values were measured spectrophotometrically using thiobarbituric acid and MDA standard
curve.
Results: Pretreatments with Glib, at both doses of 1 and 5 mg/kg or B vitamins significantly
ameliorated severity of the behavioral symptoms. Pretreatment with a combination of Glib and B
vitamins was more effective than pretreatment with Glib or B vitamins alone. Also, pretreatment
with B vitamins, Glib, or a combination of them reduced MDA concentration in the brain
suspensions. Decrease in MDA concentration in the group of rats that received a combination of B
vitamins and Glib was more prominent than that of the Glib groups.
Conclusion: As severity of the behavioral symptoms in the 6-OHDA-induced Parkinsonism
reflects the degree of the lesion in Substantia Nigra (SN) dopaminergic neurons, it is suggested
that Glib pretreatment has neuroprotective effect against 6-OHDA-induced neurotoxicity. The
current study data also showed that this effect may be mediated by antioxidant effect of Glib.

The neuroprotective role of opioid morphine against 6-hydroxydopamine-induced cell death has been demonstrated. However, the exact mechanism(s) underlying such neuroprotection, especially the role of subtype receptors, has not yet been fully clarified. Here, we investigated the effects of different opioid agonists on 6-OHDA-induced neurotoxicity in human neuroblastoma SH-SY5Y cell line as an in vitro model of Parkinson's disease. Cell damage was induced by 150 μM 6-OHDA and the cells viability was examined by MTT assay. Intracellular calcium, reactive oxygen species and mitochondrial membrane potential were assessed by fluorescence spectrophotometry method. Immunoblot technique was used to evaluate cytochrome-c and activated caspase-3 as biochemical markers of apoptosis induction. The data showed that 6-OHDA caused significant cell damage, loss of mitochondrial membrane potential and increase in intracellular reactive oxygen species and calcium levels as well as activated caspas...

Introduction: Parkinson's Disease (PD) presentations comprise frequent movement disorders
in the elderly with various symptoms consisting of motor and non-motor complications.
Paeonol is a phenolic chemical agent that has shown antioxidant and anti-inflammatory effects
in different disorders and promising effects on metabotropic glutamate receptors (mGluR)- and
GABAA-mediated neurotransmission. In this research, we tried to show the neuroprotective
potential of paeonol in rat PD model induced by intrastriatal 6-hydroxydopamine (6-OHDA).
Methods: Rats with intrastriatal 6-OHDA lesioning received with paeonol at a dosage of
100 mg/kg/d for one week. In the end, some biomarkers of oxidative stress, apoptosis, and
astrogliosis in nigral and striatal tissues were evaluated in addition to behavioral and Tyrosine
Hydroxylase (TH) immunohistochemical analysis.
Results: The obtained data showed that paeonol alleviates apomorphine-induced rotations
and reduces the delay time to initiate and the total time in the narrow beam test. However,
its beneficial behavioral effect vanished after intracerebroventricular administration of
mGluR III or GABAA receptor antagonists. Moreover, paeonol significantly restored striatal
malondialdehyde, tissue levels of reactive oxygen species, the activity of the protective
and vital enzymes consisting of superoxide dismutase and catalase, Glial Fibrillary Acidic
Protein (GFAP), DNA fragmentation, phosphor apoptosis signal-regulating kinase 1, and
nigral aquaporin 4 with no significant and proper change of nitrite, interleukin-1β, inducible
nitric oxide synthase, and angiotensin II. Additionally, paeonol prevented injury and reduced
tyrosine hydroxylase-containing neurons in the midbrain nigral tissue.
Conclusion: These obtained findings evidently designate neuroprotective property of paeonol in
6-OHDA murine model of PD that is exerted via easing of oxidative stress, apoptosis, astrogliosis,
and its advantageous effect is to some extent mediated via mGluR III/GABAA pathway

Introduction: Parkinson’s Disease (PD) is a prevalent neurodegenerative condition among the elderly. Considering the limited symptomatic improvement associated with PD treatments, introducing more effective agents is necessary. Citrus aurantium flower extract (CAE) is recognized as a neuroprotective and hepatoprotective agent with bioactive compounds, such as flavonoids, phenolics, and vitamins. Considering the mitigating role of CAE against oxidative damage, the present study examined the neuroprotective effects of CAE in a PD model.
Methods: Overall, 60 male rats were classified into 6 groups, as follows: sham (SH); control (C); lesion (L); and CAE-treated lesion (200, 400, and 600 mg/mL CAE+L). For the hemi-PD model, 6-hydroxydopamine (12.5 g/L of saline ascorbate) was injected intrastriatally. Intraperitoneal pretreatment with hydroalcoholic CAE (200, 400, and 600 mg/kg) was applied in the E+SH and E+L groups at one week pre-surgery. At two weeks post-surgery, rotational behaviors were examined by apomorphine hydrochloride. Moreover, stained neurons were measured in the Substantia Nigra pars compacta (SNc).
Results: In comparison with the C group, significant contralateral turning was reported due to apomorphine, in the L group at two weeks post-surgery (P<0.0001); while the neuron count reduced on the left SNc (P<0.05). The rotational behaviors reduced using alcoholic CAE, and reduction in the neuron count of SNc was attenuated in the lesion groups (P<0.05). However, in the SH group, CAE caused no significant effects on apomorphine-induced rotation and neuron count in the SNc. CAE could decrease the number of degenerated neurons in the SNc. Cell count assessment revealed that neural cell count significantly increased in 200, 400, and 600 mg/mL CAE groups.
Conclusion: According to the present findings, CAE can be suitable for preventing PD in rats.

Introduction: The neuroprotective role of opioid morphine against 6-hydroxydopamineinduced
cell death has been demonstrated. However, the exact mechanism(s) underlying such
neuroprotection, especially the role of subtype receptors, has not yet been fully clarified.
Methods: Here, we investigated the effects of different opioid agonists on 6-OHDA-induced
neurotoxicity in human neuroblastoma SH-SY5Y cell line as an in vitro model of Parkinson’s
disease. Cell damage was induced by 150 μM 6-OHDA and the cells viability was examined by
MTT assay. Intracellular calcium, reactive oxygen species and mitochondrial membrane potential
were assessed by fluorescence spectrophotometry method. Immunoblot technique was used to
evaluate cytochrome-c and activated caspase-3 as biochemical markers of apoptosis induction.
Results: The data showed that 6-OHDA caused significant cell damage, loss of mitochondrial
membrane potential and increase in intracellular reactive oxygen species and calcium levels
as well as activated caspase-3 and cytochrome-c release. Incubation of SH-SY5Y cells with
μ-opioid agonists, morphine and DAMGO, but not with δ-opioid agonist, DADLE, elicited
protective effect and reduced biochemical markers of cell damage and death.
Discussion: The results suggest that μ-opioid receptors signaling participate in the opioid
neuroprotective effects against 6-OHDA-induced neurotoxicity.

Oxidative stress and mitochondrial dysfunction are two pathophysiological factors often associated with the neurodegenerative process involved in Parkinson's disease (PD). Although, 6-hydroxydopamine (6-OHDA) is able to cause dopaminergic neurodegeneration in experimental models of PD by an oxidative stress-mediated process, the underlying molecular mechanism remains unclear. It has been established that some antioxidant enzymes such as catalase (CAT) and superoxide dismutase (SOD) are often altered in PD, which suggests a potential role of these enzymes in the onset and/or development of this multifactorial syndrome. In this study we have used high-resolution respirometry to evaluate the effect of 6-OHDA on mitochondrial respiration of isolated rat brain mitochondria and the lactate dehydrogenase cytotoxicity assay to assess the percentage of cell death induced by 6-OHDA in human neuroblastoma cell line SH-SY5Y. Our results show that 6-OHDA affects mitochondrial respiration by causing a reduction in both respiratory control ratio (IC(50) = 200 ± 15 nM) and state 3 respiration (IC(50) = 192 ± 17 nM), with no significant effects on state 4(o). An inhibition in the activity of both complex I and V was also observed. 6-OHDA also caused cellular death in human neuroblastoma SH-SY5Y cells (IC(50) = 100 ± 9 μM). Both SOD and CAT have been shown to protect against the toxic effects caused by 6-OHDA on mitochondrial respiration. However, whereas SOD protects against 6-OHDA-induced cellular death, CAT enhances its cytotoxicity. The here reported data suggest that both superoxide anion and hydroperoxyl radical could account for 6-OHDA toxicity. Furthermore, factors reducing the rate of 6-OHDA autoxidation to its p-quinone appear to enhance its cytotoxicity.