Genetic silencing of striatal CaV1.3 prevents and ameliorates levodopa dyskinesia.

BACKGROUND: Levodopa-induced dyskinesias are an often debilitating side effect of levodopa therapy in Parkinson's disease. Although up to 90% of individuals with PD develop this side effect, uniformly effective and well-tolerated antidyskinetic treatment remains a significant unmet need. The pathognomonic loss of striatal dopamine in PD results in dysregulation and disinhibition of striatal CaV1.3 calcium channels, leading to synaptopathology that appears to be involved in levodopa-induced dyskinesias. Although there are clinically available drugs that can inhibit CaV1.3 channels, they are not adequately potent and have only partial and transient impact on levodopa-induced dyskinesias. METHODS: To provide unequivocal target validation, free of pharmacological limitations, we developed a CaV1.3 shRNA to provide high-potency, target-selective, mRNA-level silencing of striatal CaV1.3 channels and examined its ability to impact levodopa-induced dyskinesias in severely parkinsonian rats. RESULTS: We demonstrate that vector-mediated silencing of striatal CaV1.3 expression in severely parkinsonian rats prior to the introduction of levodopa can uniformly and completely prevent induction of levodopa-induced dyskinesias, and this antidyskinetic benefit persists long term and with high-dose levodopa. In addition, this approach is capable of ameliorating preexisting severe levodopa-induced dyskinesias. Importantly, motoric responses to low-dose levodopa remained intact in the presence of striatal CaV1.3 silencing, indicating preservation of levodopa benefit without dyskinesia liability. DISCUSSION: The current data provide some of the most profound antidyskinetic benefit reported to date and suggest that genetic silencing of striatal CaV1.3 channels has the potential to transform treatment of individuals with PD by allowing maintenance of motor benefit of levodopa in the absence of the debilitating levodopa-induced dyskinesia side effect. © 2019 The Authors. Movement Disorders published by Wiley Periodicals, Inc. on behalf of International Parkinson and Movement Disorder Society.

6-Hydroxydopamine induces different mitochondrial bioenergetics response in brain regions of rat.

Mitochondrial dysfunction has been demonstrated to have a central role in Parkinson Disease (PD) pathophysiology. Some studies have indicated that PD causes an impairment in mitochondrial bioenergetics; however, the effects of PD on brain-region specific bioenergetics was never investigated before. This study aimed to evaluate mitochondrial bioenergetics in different rat brain structures in an in vitro model of PD using 6-OHDA. Rat brain slices of hippocampus, striatum, and cortex were exposed to 6-OHDA (100 µM) for 1 h and mitochondrial bioenergetic parameters, peroxide production, lactate dehydrogenase (LDH) and citrate synthase (CS) activities were analyzed. Hippocampus slices exposed to 6-OHDA presented increased peroxide production but, no mitochondrial adaptive response against 6-OHDA damage. Cortex slices exposed to 6-OHDA presented increased oxygen flux related to oxidative phosphorylation and energetic pathways exchange demonstrated by the increase in LDH activity, suggesting a mitochondrial compensatory response. Striatum slices exposed to 6-OHDA presented a decrease of oxidative phosphorylation and decrease of oxygen flux related to ATP-synthase indicating an impairment in the respiratory chain. The co-incubation of 6-OHDA with n-acetylcysteine (NAC) abolished the effects of 6-OHDA on mitochondrial function in all brain regions tested, indicating that the increased reactive oxygen species (ROS) production is responsible for the alterations observed in mitochondrial bioenergetics. The present results indicate a brain-region specific response against 6-OHDA, providing new insights into brain mitochondrial bioenergetic function in PD. These findings may contribute to the development of future therapies with a target on energy metabolism.

Anacardium microcarpum Promotes Neuroprotection Dependently of AKT and ERK Phosphorylation but Does Not Prevent Mitochondrial Damage by 6-OHDA.

Parkinson's disease is a degenerative and progressive illness characterized by the degeneration of dopaminergic neurons. 6-hydroxydopamine (6-OHDA) is a widespread model for induction of molecular and behavioral alterations similar to Parkinson and has contributed for testing of compounds with neuroprotective potential. The Brazilian plant Anacardium microcarpum is used in folk medicine for treatment of several illnesses; however, the knowledge about toxicology and biological effects for this plant is very rare. The neuroprotective effect from hydroalcoholic extract and methanolic and acetate fraction of A. microcarpum on 6-OHDA-induced damage on chicken brain slices was investigated in this study. 6-OHDA decreased cellular viability measured by MTT reduction assay, induced lipid peroxidation by HPLC, stimulated Glutathione-S-Transferase and Thioredoxin Reductase activity, and decreased Glutathione Peroxidase activity and the total content of thiols containing compounds. The methanolic fraction of A. microcarpum presented the better neuroprotective effects in 6-OHDA-induced damage in relation with hydroalcoholic and acetate fraction. The presence of AKT and ERK1/2 pharmacological inhibitors blocked the protective effect of methanolic fraction suggesting the involvement of survival pathways in the neuroprotection by the plant. The plant did not prevent 6-OHDA autoxidation or 6-OHDA-induced mitochondrial dysfunction. Thus, the neuroprotective effect of the methanolic fraction of A. microcarpum appears to be attributed in part to chelating properties of extract toward reactive species and is dependent on ERK1/2 and AKT phosphorylation. This study contributes to the understanding of biochemical mechanisms implied in neuroprotective effects of the vegetal species A. microcarpum.

Electroacupuncture Alleviates Motor Symptoms and Up-Regulates Vesicular Glutamatergic Transporter 1 Expression in the Subthalamic Nucleus in a Unilateral 6-Hydroxydopamine-Lesioned Hemi-Parkinsonian Rat Model.

Previous studies have shown that electroacupuncture (EA) promotes recovery of motor function in Parkinson's disease (PD). However the mechanisms are not completely understood. Clinically, the subthalamic nucleus (STN) is a critical target for deep brain stimulation treatment of PD, and vesicular glutamate transporter 1 (VGluT1) plays an important role in the modulation of glutamate in the STN derived from the cortex. In this study, a 6-hydroxydopamine (6-OHDA)-lesioned rat model of PD was treated with 100 Hz EA for 4 weeks. Immunohistochemical analysis of tyrosine hydroxylase (TH) showed that EA treatment had no effect on TH expression in the ipsilateral striatum or substantia nigra pars compacta, though it alleviated several of the parkinsonian motor symptoms. Compared with the hemi-parkinsonian rats without EA treatment, the 100 Hz EA treatment significantly decreased apomorphine-induced rotation and increased the latency in the Rotarod test. Notably, the EA treatment reversed the 6-OHDA-induced down-regulation of VGluT1 in the STN. The results demonstrated that EA alleviated motor symptoms and up-regulated VGluT1 in the ipsilateral STN of hemi-parkinsonian rats, suggesting that up-regulation of VGluT1 in the STN may be related to the effects of EA on parkinsonian motor symptoms via restoration of function in the cortico-STN pathway.

Pathway-Specific Remodeling of Thalamostriatal Synapses in Parkinsonian Mice.

Movement suppression in Parkinson's disease (PD) is thought to arise from increased efficacy of the indirect pathway basal ganglia circuit, relative to the direct pathway. However, the underlying pathophysiological mechanisms remain elusive. To examine whether changes in the strength of synaptic inputs to these circuits contribute to this imbalance, we obtained paired whole-cell recordings from striatal direct- and indirect-pathway medium spiny neurons (dMSNs and iMSNs) and optically stimulated inputs from sensorimotor cortex or intralaminar thalamus in brain slices from control and dopamine-depleted mice. We found that dopamine depletion selectively decreased synaptic strength at thalamic inputs to dMSNs, suggesting that thalamus drives asymmetric activation of basal ganglia circuitry underlying parkinsonian motor impairments. Consistent with this hypothesis, in vivo chemogenetic and optogenetic inhibition of thalamostriatal terminals reversed motor deficits in dopamine-depleted mice. These results implicate thalamostriatal projections in the pathophysiology of PD and support interventions targeting thalamus as a potential therapeutic strategy.

Subthalamic deep brain stimulation reduces pathological information transmission to the thalamus in a rat model of parkinsonism.

The degeneration of dopaminergic neurons in the substantia nigra pars compacta leads to parkinsonian motor symptoms via changes in electrophysiological activity throughout the basal ganglia. High-frequency deep brain stimulation (DBS) partially treats these symptoms, but the mechanisms are unclear. We hypothesize that motor symptoms of Parkinson's disease (PD) are associated with increased information transmission from basal ganglia output neurons to motor thalamus input neurons and that therapeutic DBS of the subthalamic nucleus (STN) treats these symptoms by reducing this extraneous information transmission. We tested these hypotheses in a unilateral, 6-hydroxydopamine-lesioned rodent model of hemiparkinsonism. Information transfer between basal ganglia output neurons and motor thalamus input neurons increased in both the orthodromic and antidromic directions with hemiparkinsonian (hPD) onset, and these changes were reversed by behaviorally therapeutic STN-DBS. Omnidirectional information increases in the parkinsonian state underscore the detrimental nature of that pathological information and suggest a loss of information channel independence. Therapeutic STN-DBS reduced that pathological information, suggesting an effective increase in the number of independent information channels. We interpret these data with a model in which pathological information and fewer information channels diminishes the scope of possible motor activities, driving parkinsonian symptoms. In this model, STN-DBS restores information-channel independence by eliminating or masking the parkinsonism-associated information, and thus enlarges the scope of possible motor activities, alleviating parkinsonian symptoms.

Oxidative stress mediated neuronal damage in the corpus striatum of 6-hydroxydopamine lesioned Parkinson's rats: neuroprotection by serotonin, GABA and bone marrow cells supplementation.

Oxidative stress-induced neuronal cell death has been implicated in Parkinson's disease (PD). Oxidative stress initiated by 6-hydroxydopamine (6-OHDA) causes mitochondrial dysfunction leading to apoptosis and Parkinsonian neurodegeneration. We investigated the neuroprotective potential of serotonin (5-HT), gamma amino butyric acid (GABA) and autologous bone marrow cells (BMC) in combination against oxidative stress-induced cell death. PD was induced in adult male Wistar rats by intranigral infusion of 6-OHDA (8 µg/µl). The activities of antioxidant enzymes--superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx) were analysed. The extent of lipid peroxidation was quantified by measuring the formation of thiobarbituric acid reactive substances (TBARs). Real Time PCR gene expression of SOD, CAT and GPx were performed using specific Taqman probes. 6-OHDA induced decreased activity of SOD, CAT and GPx in corpus striatum was significantly reversed to near control (p<0.001) by treatment with 5-HT, GABA and bone marrow cells. Gene expression studies of SOD, CAT and GPx using Real Time PCR confirmed the above observation. TBAR levels were elevated (p<0.001) in 6-OHDA treated rats indicating lipid peroxidation. 5-HT and GABA along with autologous bone marrow cell supplementation significantly ameliorated 6-OHDA-induced lipid peroxidation (p<0.001). Our results suggest a new therapeutic strategy of neuroprotection against damage by oxidative stress in Parkinson's disease.

High intake of folic acid or complex of B vitamins provides anti-Parkinsonism effect: no role for serum level of homocysteine.

Several lines of evidence show that homocysteine (Hcy) levels are increased in blood and CSF of patients with Parkinson's disease. B vitamins are necessary for Hcy metabolism and their deficiencies cause hyperhomocysteinemia and neurodegeneration. In present study, effect of B vitamin supplementation on the severity of 6-hydroxydopamine (6-OHDA)-induced Parkinsonism was investigated. Rats were nourished with B vitamin supplements from 1 month before of stereotaxic injection of 6-OHDA to the end of experiments. Total serum Hcy was measured at the end of experiments to identify its association with Parkinsonism. Both rotational and rotarod tests revealed that supplementation of folic acid, in a dose dependent manner, attenuates severity of Parkinsonism. Supplement of B complex also had beneficial effect and improved motor performance in rotarod test and decreased biased swings in elevated body swing test but had no effect on the apomorphine-induced rotational behavior. Supplement of B(6) attenuated rotational behavior but had no effect on the rotarod performance and swinging behavior. Supplement of B(12) or combination of folic acid with B(6) and B(12) had no effect on the behavioral symptoms of Parkinsonism. Except one group, the levels of Hcy in other vitamin B treated groups were near to that in control group. Surprisingly, Hcy in group of rats that received high intake of folic acid was significantly higher than that in control group. Our results indicate that high intake of folic acid or B complex provides anti-Parkinsonism effect but it is not mediated by lowering plasma Hcy.

Toxicological effects of a mixture used in weight loss products: p-synephrine associated with ephedrine, salicin, and caffeine.

p-Synephrine is an adrenergic amine found in Citrus aurantium L. fruits and has been used for weight loss in dietary supplements. There are commercial products containing this substance associated to caffeine, salicin, and ephedrine. The aim of this study was to evaluate the acute toxicity of this mixture in mice of both sexes. The significative results observed after acute oral administration to male and female mice of 300, 350, and 400 mg/kg total of p-synephrine, ephedrine, salicin, plus caffeine in a 10:4:6:80 w/w ratio included a reduction in locomotor activity and ptosis in all treated groups for both sexes. Seizures were also observed in male (400 mg/kg) and female groups (350 and 400 mg/kg). Gasping and tearing were observed in males. Salivation (400 mg/kg), agitation (350 and 400 mg/kg), and piloerection (all treated groups) were significantly observed only in females. Deaths occurred in males at 350 and 400 mg/kg treated groups and the necropsy showed cardiopulmonary hemorrhage. A reduction in locomotor activity was confirmed through the spontaneous locomotor activity test, in which the number of crossings considerably decreased (P < .01) in all treated groups. The rotarod test showed a decrease in motor coordination at 400 mg/kg. Body temperature decreased significantly (P < .01) in all treated groups compared to controls. The results suggested clear signs of toxicity of p-synephrine, ephedrine, salicin, and caffeine association; this toxicity augments the attentiveness on commercial products containing this mixture, given the expressive number of adverse events related to its utilization.

Acupuncture inhibits oxidative stress and rotational behavior in 6-hydroxydopamine lesioned rat.

Increasing evidence suggests the beneficial effects of acupuncture on Parkinson's disease (PD). Although clinical evidence for the acupuncture anti-Parkinson's disease effect has been demonstrated, the precise mechanism still remains elusive. It has been suggested a relationship between PD and reactive oxygen species (ROS) can result in neurodegeneration. The aim of this study was to evaluate the status of oxidative stress, as well as the antioxidant enzyme response, and the role of acupuncture stimulation at GB34 (Yanglingquan), LR3 (Taichong), ST36 (Zusanli) and SP10 (Xuehai) acupoints on regulating oxidative stress in the nigrostriatal system in the 6-hydroxydopamine (6-OHDA) lesioned rat. Two weeks after unilateral injection of 6-OHDA into the left medial forebrain bundle (MFB), an apomorphine induced rotational behavior test was performed. The levels of enzymatic, viz., superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), catalase (CAT), and nonenzymatic, viz., reduced glutathione (GSH), and the levels of malondialdehyde (MDA) in the nigrostriatal system were measured to assess the oxidative stress status. Brain MDA levels significantly increased, while GSH levels were decreased in impaired groups with 6-OHDA injection only, accompanied by a marked reduction in the level of SOD and GSH-Px. The levels of oxidative stress related parameters except CAT, as well as the rotational asymmetry, were reversed by acupuncture stimulation. These results showed that acupuncture treatment displayed antioxidative and/or neuroprotective properties in the 6-OHDA lesioned rat and these protective properties might be mediated, at least in part, by involving regulation of the antioxidant defense system.

Dopamine D1 receptor gene expression studies in unilateral 6-hydroxydopamine-lesioned Parkinson's rat: effect of 5-HT, GABA, and bone marrow cell supplementation.

Parkinson's disease is the second most common neurodegenerative disorder and remains incurable. Many potential compensatory mechanisms have now been proposed; these are both dopaminergic, focused on enhancing effects or exposure to existing dopamine, and non-dopaminergic, being focused on reducing activity of the indirect striatal output pathway. In the present study, the effects of serotonin, gamma-aminobutyric acid, and bone marrow cell supplementation intranigrally to the substantia nigra on unilateral 6-hydroxydopamine-infused rats were analyzed individually. Dopaminergic binding parameters were done by Scatchard analysis of dopamine D(1) receptor-binding assay using [(3)H]SCH 23390. In the corpus striatum, 6-hydroxydopamine-infused rats showed a significant decrease in B (max) (P < 0.001), and in cerebral cortex, they showed a significant increase in B (max) (P < 0.001) compared to control. Real-time polymerase chain reaction amplification of dopamine D(1) was downregulated (P < 0.001) in the corpus striatum of 6-hydroxydopamine-infused rats compared to control, whereas in the cerebral cortex, it showed a significant upregulation (P < 0.001). Behavioral studies were carried out to confirm the biochemical and molecular studies. Serotonin and gamma-aminobutyric acid supplementation reversed these changes to control. The bone marrow cell-treated group of our studies does not show much significant change as compared to the serotonin and gamma-aminobutyric acid-supplemented groups. The alterations in dopamine D(1) receptor-binding parameters and gene expression during Parkinson's model were reversed by serotonin and gamma-aminobutyric acid supplementation in our experiments, which has clinical significance in the management of the disease.

Oral pre-treatment with epigallocatechin gallate in 6-OHDA lesioned rats produces subtle symptomatic relief but not neuroprotection.

Much recent work is investigating the role of oxidative stress and inflammatory mechanisms in the aetiology of neurodegeneration in Parkinson's disease. The present study evaluated whether the green tea constituent epigallocatechin gallate (EGCG) which has both anti-oxidant and anti-inflammatory properties, exerts neuroprotection and symptomatic effects when administered orally as a pre-treatment prior to 6-hydroxydopamine (6-OHDA) lesions. Groups of rats were given either 1mg/kg, 2mg/kg EGCG or vehicle solution for 14 days. Sham or 6-OHDA surgery was performed on day 11 of the drug administration protocol. Behavioural analysis was conducted before drugs/vehicle solution, again during the treatment period and then repeated at fortnightly intervals for 2 months post-operatively. Whilst some subtle behavioural improvements in postural abnormalities and ability to cross a narrow beam were observed in lesioned rats after EGCG (vs. vehicle) there was no evidence of neuroprotection on post-mortem quantification of degree of nigral dopaminergic neuronal loss when comparing the lesioned groups given the various treatments.

Screening for in vivo (anti)estrogenic activity of ephedrine and p-synephrine and their natural sources Ephedra sinica Stapf. (Ephedraceae) and Citrus aurantium L. (Rutaceae) in rats.

Formulations containing Ephedra sinica Stapf. (Ephedraceae) and Citrus aurantium L. (Rutaceae) are consumed worldwide for body weight control. Considering the related adverse effects and the risk potential, the aim of this study is to evaluate the effects of the thermogenic compounds ephedrine, p-sinephrine, E. sinica and C. aurantium in the female reproductive system through the uterotrophic assay in immature female rats. The animals (n = 6-7) received E. sinica 85.5 and 855.0 mg/kg/day, C. aurantium 25.0 and 50.0 mg/kg/day, ephedrine 5.0 mg/kg/day and p-synephrine 50.0 mg/kg/day for three consecutive days by oral gavage. For detection of antiestrogenicity, tamoxifen 20.0 mg/kg/day, E. sinica 855.0 mg/kg/day, C. aurantium 50.0 mg/kg/day, ephedrine 5.0 mg/kg/day and p-synephrine 50.0 mg/kg/day were administered to estrogen-treated females. Macroscopical alterations were evaluated in liver, kidneys, adrenals and uterus. All analyzed substances showed an antiestrogenic potential, but only ephedrine at 0.5 mg/kg/day presented a significative antiestrogenic effect (P < 0.01). Adrenals relative mass were reduced (P < 0.01) in all tested compounds when compared to the control, which seems to be related to the alfa-1-adrenoceptor agonist activity, which promote a vasoconstriction and reduction of the liquid in the organ. The endocrine system is highly complex and there are a number of ways in which a chemical may interfere with it, other in vivo and in vitro assays are being necessary to support this mechanism of action.

Preventive effects of genistein on motor dysfunction following 6-hydroxydopamine injection in ovariectomized rats.

Estrogen and phytoestrogens such as the isoflavones have received considerable attention in Parkinson's disease (PD) research. Because they have been reported to possess neuroprotective effects on dopaminergic neurons in the substantia nigra (SN), isoflavones appear particularly promising for post-menopausal women at risk for PD. However, most previous studies were limited to morphological investigation, and the preventive effects of isoflavones on motor function have not been evaluated. The aim of the present study was to elucidate the prevention by an isoflavone against motor dysfunction after injection of 6-hydroxydopamine (6-OHDA) into the medial forebrain bundle of ovariectomized rats, which mimics post-menopausal status in women. Pretreatment with genistein, an isoflavone, significantly preserved motor function in rats injected with low-dose 6-OHDA, as evaluated by the stepping and cylinder tests. An estrogen receptor antagonist, ICI182780, reversed the effects of genistein, indicating that this effect of genistein is mediated through estrogen receptors. The functional effects of genistein were accompanied by preservation of tyrosine hydroxylase-immunoreactive neurons in the SN after injection of low-dose 6-OHDA. These findings suggest that genistein may be useful for the prevention of PD in post-menopausal women.

Dietary oxyresveratrol prevents parkinsonian mimetic 6-hydroxydopamine neurotoxicity.

Oxyresveratrol (OXY) is a polyhydroxylated stilbene existing in mulberry. Increasing lines of evidence have shown its neuroprotective effects against Alzheimer disease and stroke. However, little is known about its neuroprotective effect in Parkinson disease (PD). Owing to its antioxidant activity, blood-brain barrier permeativity, and water solubility, we hypothesized that OXY may exert neuroprotective effects against parkinsonian mimetic 6-hydroxydopamine (6-OHDA) neurotoxicity. Neuroblastoma SH-SY5Y cells have long been used as dopaminergic neurons in PD research. We found that both pretreatment and posttreatment with OXY on SH-SY5Y cells significantly reduced the release of lactate dehydrogenase, the activity of caspase-3, and the generation of intracellular reactive oxygen species triggered by 6-OHDA. Compared to resveratrol, OXY exhibited a wider effective dosage range. We proved that OXY could penetrate the cell membrane by HPLC analysis of cell extracts. These results suggest that OXY may act as an intracellular antioxidant to reduce oxidative stress induced by 6-OHDA. Western blot analysis demonstrated that OXY markedly attenuated 6-OHDA-induced phosphorylation of JNK and c-Jun. Furthermore, we proved that OXY increased the basal levels of SIRT1, which may disclose new pathways accounting for the neuroprotective effects of OXY. Taken together, our results suggest OXY, a dietary phenolic compound, as a potential nutritional candidate for protection against neurodegeneration in PD.

Protective effects of green tea polyphenols in the 6-OHDA rat model of Parkinson's disease through inhibition of ROS-NO pathway.

BACKGROUND: Nitric oxide (NO) and related pathways are thought to play an important role in the pathogenesis of Parkinson's disease (PD). Our in vitro experiments suggested that green tea polyphenols (GTP) might protect dopamine neurons through inhibition of NO and reactive oxygen species (ROS). METHODS: Immunohistochemistry, terminal deoxynucleotidyl transferase-mediated dUTP Nick End Labeling assay, electron spin resonance spin trapping, enzyme linked immunosorbent assay, and molecular biological methods were used to investigate the effects of GTP in an unilateral 6-hydroxydopamine (6-OHDA)-treated rat model of PD. RESULTS: GTP treatment dose-dependently protected dopaminergic neurons by preventing from midbrain and striatal 6-OHDA-induced increase in 1) both ROS and NO levels, 2) lipid peroxidation, 3) nitrite/nitrate content, 4) inducible nitric oxide synthase, and 5) protein-bound 3-nitro-tyrosine. Moreover, GTP treatment dose-dependently preserved the free radical scavenging capability of both the midbrain and the striatum. CONCLUSIONS: These results support the in vivo protection of GTP against 6-OHDA and suggest that GTP treatment might represent a neuroprotective treatment of PD.

The differential effects of 5-HT(1A) receptor stimulation on dopamine receptor-mediated abnormal involuntary movements and rotations in the primed hemiparkinsonian rat.

Serotonin 1A receptor (5-HT(1A)R) agonists have emerged as valuable supplements to l-DOPA therapy, demonstrating that they can decrease side effects and enhance motor function in animal models of Parkinson's disease (PD) and human PD patients. The precise mechanism by which these receptors act remains unknown and there is limited information on how 5-HT(1A)R stimulation impacts striatal dopamine (DA) D1 receptor (D1R) and D2 receptor (D2R) function. The current study examined the effects of 5-HT(1A)R stimulation on DA receptor-mediated behaviors. Male Sprague-Dawley rats were rendered hemiparkinsonian by unilateral 6-OHDA lesions and primed with the D1R agonist SKF81297 (0.8 mg/kg, i.p.) in order to sensitize DA receptors. Using a randomized within subjects design, rats received a first injection of: Vehicle (dH(2)O) or the 5-HT(1A)R agonist +/-8-OH-DPAT (0.1 or 1.0 mg/kg, i.p.), followed by a second injection of: Vehicle (dimethyl sulfoxide), the D1R agonist SKF81297 (0.8 mg/kg, i.p.), the D2R agonist quinpirole (0.2 mg/kg, i.p.), or l-DOPA (12 mg/kg+benserazide, 15 mg/kg, i.p.). On test days, rats were monitored over a 2-h period immediately following the second injection for abnormal involuntary movements (AIMs), analogous to dyskinesia observed in PD patients, and contralateral rotations. The present findings indicate that 5-HT(1A)R stimulation reduces AIMs induced by D1R, D2R and l-DOPA administration while its effects on DA agonist-induced rotations were receptor-dependent, suggesting that direct 5-HT(1A)R and DA receptor interactions may contribute to the unique profile of 5-HT(1A)R agonists for the improvement of PD treatment.

Acute hemorrhagic myocardial necrosis and sudden death of rats exposed to a combination of ephedrine and caffeine.

Because of possible side effects of herbal medicines containing ephedrine and guarana-derived caffeine, including increased risk of stroke, myocardial infarction, and sudden death, the Food and Drug Administration recently banned the sale of ephedra-containing products, specifically over-the-counter dietary supplements. We report cardiac in 7- and 14-week-old male F344 rats exposed by gavage to ephedrine(25 mg/kg) and caffeine (30 mg/kg) administered in combination for one or two days. The ephedrine-caffeine dosage was approximately 12- and 1.4-fold, respectively, above average human exposure, based on a mg/m2 body surface-area comparison. Several (5/7) of the exposed 14-week-old rats died or were sacrificed in extremis 4-5 h after the first dosing. In these hearts, changes were observed chiefly in the interventricular septum but also left and right ventricular walls. Massive interstitial hemorrhage, with degeneration of myofibers, occurred at the subendocardial myocardium of the left ventricle and interventricular septum. Immunostaining for cleaved caspase-3 and hyperphosphorylated H2A.X, a histone variant that becomes hyperphosphorylated during apoptosis, indicated multifocal generalized positive staining of degenerating myofibers and fragmenting nuclei, respectively. The Barbeito-Lopez trichrome stain revealed generalized patchy yellow myofibers consistent with degeneration and/or coagulative necrosis. In ephedrine-caffeine-treated animals terminated after the second dosing, foci of myocardial degeneration and necrosis were already infiltrated by mixed inflammatory cells. The myocardial necrosis may occur secondarily to intense diffuse vasoconstriction of the coronary arterial system with decreased myocardial perfusion. Our work shows the direct relationship between combined ephedrine and caffeine exposure and cardiac pathology.

Lesions of the dorsal noradrenergic bundle augment the renin response to blood loss but do not alter hypothalamic Fos expression.

The goal of this study was to determine if the dorsal noradrenergic bundle (DNAB) plays an essential role in mediating increased plasma renin activity (PRA) and hypothalamic activation, as indicated by increased Fos expression, in response to a small volume blood loss in unanesthetized animals. Male Sprague-Dawley rats were prepared with bilateral 6-hydroxydopamine or sham lesions of the dorsal noradrenergic bundle. In both groups of animals, blood pressure decreased by only 10-15 mmHg following hemorrhage (10 ml/kg over 15 min). Plasma renin activity increased similarly in both groups after 5 ml/kg blood loss, but showed a significantly greater increase after 10 ml/kg blood loss in animals with 6-hydroxydopamine lesions than in those with sham lesions (increase of 13.8 +/- 2.0 ng/ml/h versus 8.4 +/- 1.2 ng/ml/h; P < 0.025). There were numerous Fos-immunoreactive cell nuclei in the supraoptic nucleus (SON) and parvicellular paraventricular hypothalamic nucleus (PVN) of hemorrhaged animals. The number of Fos-positive neurons did not differ between groups, indicating that the dorsal noradrenergic bundle does not convey the primary drive for supraoptic and paraventricular nucleus activation during blood loss. However, one or more of the forebrain regions innervated by the dorsal noradrenergic bundle may attenuate the sympathetic outflow that initiates renin release in response to hemorrhage.

Potentiation of parkinsonian symptoms by depletion of locus coeruleus noradrenaline in 6-hydroxydopamine-induced partial degeneration of substantia nigra in rats.

Parkinson's disease is characterized not only by a progressive loss of dopaminergic neurons in the substantia nigra but also by a degeneration of locus coeruleus noradrenergic neurons. The present study addresses the question of whether a partial neurodegeneration of dopaminergic neurons using 6-hydroxydopamine in rat, not sufficient to produce motor disturbances, is potentiated by prior selective denervation of locus coeruleus noradrenergic terminal fields using N-ethyl-2-bromobenzylamine. Two types of denervations, one causing dopamine deficiency alone and the other causing noradrenaline and dopamine deficiency, were performed. Noradrenaline, 5-hydroxytryptamine, 5-hydroxyindole acetic acid, dopamine and its metabolites were analysed in various brain regions. Behaviour was evaluated by catalepsy tests and activity box. N-ethyl-2-bromobenzylamine selectively depleted noradrenaline from neurons of locus coeruleus origin. Decreased dopamine content in the striatum, substantia nigra and pre-frontal cortex was observed after dopaminergic lesion with 6-hydroxydopamine (42.9%). Additional locus coeruleus noradrenaline depletion with N-ethyl-2-bromobenzylamine aggravated the dopamine depletion (61.2%). The lesion in the noradrenergic and dopaminergic neurodegenerated group was not sufficient to induce consistent catalepsy and akinesia. However, after a subthreshold dose of haloperidol (0.1 mg/kg), the expression of catalepsy and akinesia was strong in the dual-lesioned group and less in the 6-hydroxydopamine-lesioned group. These results indicate that denervation of locus coeruleus noradrenergic terminals with N-ethyl-2-bromobenzylamine potentiates the 6-hydroxydopamine-induced partial dopaminergic neurodegeneration and parkinsonian symptoms. Based on the present findings and existing reports, it can be concluded that noradrenergic neurons of locus coeruleus have neuromodulatory and neuroprotective properties on the dopaminergic neurons of basal ganglia and that noradrenergic degeneration may contribute to the aetiology and pathophysiology of Parkinson's disease.