Dysautonomias in Parkinson's disease: cardiovascular changes and autonomic modulation in conscious rats after infusion of bilateral 6-OHDA in substantia nigra

Combining blood pressure variability and heart rate variability to analyze the autonomic nervous function of rotenone induced Parkinson's rat model

BACKGROUND

Parkinson's patients have significant autonomic dysfunction, early detect the disorder is a major challenge. To assess the autonomic function in the rat model of rotenone induced Parkinson's disease (PD), Blood pressure and ECG signal acquisition are very important.

NEW METHOD

We used telemetry to record the electrocardiogram and blood pressure signals from awake rats, with linear and nonlinear analysis techniques calculate the heart rate variability (HRV) and blood pressure variability (BPV). we applied nonlinear analysis methods like sample entropy and detrended fluctuation analysis to analyze blood pressure signals. Particularly, this is the first attempt to apply nonlinear analysis to the blood pressure evaluate in rotenone induced PD model rat.

RESULTS

HRV in the time and frequency domains indicated sympathetic-parasympathetic imbalance in PD model rats. Linear BPV analysis didn't reflect changes in vascular function and blood pressure regulation in PD model rats. Nonlinear analysis revealed differences in BPV, with lower sample entropy results and increased detrended fluctuation analysis results in the PD group rats.

COMPARISON WITH EXISTING METHODS AND CONCLUSIONS

our experiments demonstrate the ability to evaluate autonomic dysfunction in models of Parkinson's disease by combining the analysis of BPV with HRV, consistent with autonomic impairment in PD patients. Nonlinear analysis by blood pressure signal may help in early detection of the PD. It indicates that the fluctuation of blood pressure in the rats in the rotenone model group tends to be regular and predictable, contributes to understand the PD pathophysiological mechanisms and to find strategies for early diagnosis.

Role of cardiac β1-adrenergic and A1-adenosine receptors in severe arrhythmias related to Parkinson's disease

AIMS

Although reduced life expectancy in Parkinson's Disease (PD) patients has been related to severe cardiac arrhythmias due to autonomic dysfunctions, its molecular mechanisms remain unclear. To investigate the role of cardiac β1-Adrenergic (β1AR) and A1-Adenosine (A1R) receptors in these dysfunctions, the pharmacological effects of stimulation of cardiac β1AR (isoproterenol, ISO), in the absence and presence of cardiac β1AR (atenolol, AT) or A1R (1,3-dipropyl-8-cyclopentyl xanthine, DPCPX) blockade, on the arrhythmias induced by Ischemia/Reperfusion (CIR) in an animal PD model were studied.

METHODS

PD was produced by dopaminergic lesions (confirmed by immunohistochemistry analysis) caused by the injection of 6-hydroxydopamine (6-OHDA, 6 μg) in rat striatum. CIR was produced by a surgical interruption for 10 min followed by reestablishment of blood circulation in the descendent left coronary artery. On the incidence of CIR-Induced Ventricular Arrhythmias (VA), Atrioventricular Block (AVB), and Lethality (LET), evaluated by Electrocardiogram (ECG) analysis, the effects of intravenous treatment with ISO, AT and DPCPX (before CIR) were studied.

RESULTS

VA, AVB and LET incidences were significantly higher in 6-OHDA (83%, 92%, 100%, respectively) than in control rats (58%, 67% and 67%, respectively). ISO treatment significantly reduced these incidences in 6-OHDA (33%, 33% and 42%, respectively) and control rats (25%, 25%, 33%, respectively), indicating that stimulation of cardiac β1AR induced cardioprotection. This response was prevented by pretreatment with AT and DPCPX, confirming the involvement of cardiac β1AR and A1R.

CONCLUSION

Pharmacological modulation of cardiac β1AR and A1R could be a potential therapeutic strategy to reduce severe arrhythmias and increase life expectancy in PD patients.

Role of the iNOS isoform in the cardiovascular dysfunctions of male rats with 6-OHDA-induced Parkinsonism

INTRODUCTION

Available studies have shown the involvement of nitric oxide (NO) in the processes that lead to neurodegeneration in PD. Also, the use of inhibitors of the inducible isoform of NO-synthase (iNOS) promotes neuroprotection and attenuates dopamine (DA) loss in experimental models of Parkinsonism. In addition, NO also appears to be involved in cardiovascular changes in 6-hydroxydopamine (6-OHDA)-induced Parkinsonism. The current study aimed to evaluate the effects of iNOS inhibition on cardiovascular and autonomic function in animals that were subjected to Parkinsonism by the administration of 6-OHDA.

MATERIALS AND METHODS

The animals underwent stereotaxic surgery for bilateral microinfusion of the neurotoxin 6-OHDA (6 mg/mL in 0.2% ascorbic acid in sterile saline solution) or vehicle solution for the Sham group. From the day of stereotaxis until the day of femoral artery catheterization, the animals were treated with the iNOS inhibitor, S-methylisothiourea (SMT; 10 mg/kg; i.p.) or saline solution (0.9%; i.p.) for 7 days. The animals were divided into four groups: Sham-Saline, Sham-SMT, 6-OHDA-Saline, and 6-OHDA-SMT. Subsequent analyses were performed on these four groups. After 6 days, they underwent catheterization of the femoral artery, and 24 hours later, mean arterial pressure (MAP) and heart rate (HR) were recorded. Another group of animals (the 6-OHDA and Sham groups) was assessed for aortic vascular reactivity after 7 days of bilateral infusion of 6-OHDA or vehicle, in which cumulative concentration-effect curves (CCEC) were made for phenylephrine (Phenyl), acetylcholine and sodium nitroprusside (NPS). Also, CCEC in the presence of Nw-nitro-arginine-methyl-ester (l-NAME) (10-5 M), SMT (10-6 M), and indomethacin (10-5M) blockers were made.

RESULTS

The effectiveness of the 6-OHDA lesion was confirmed with the reduction of DA in 6-OHDA animals. However, treatment with SMT could not reverse the loss of DA. Concerning the baseline parameters, SBP and MAP values were lower in 6-OHDA animals compared to their Sham control, with no effect of treatment with SMT. In the analysis of SBP variability, a decrease in variance, the VLFabs component, and the LFabs component were observed in the 6-OHDA groups when compared to their controls, regardless of treatment with SMT. It was also observed that intravenous injections of SMT resulted in an increase in BP and a decrease in HR. However, the response was not different between the Sham and 6-OHDA groups. In vascular function, there was a hyporeactivity to Phenyl in the 6-OHDA group, and when investigating the mechanisms of this hyporeactivity, it was seen that the Rmax to Phenyl increased with incubation with SMT, indicating that iNOS could be involved in the vascular hyporeactivity of animals with Parkinsonism.

CONCLUSION

Thus, the set of results presented in this study suggests that part of the cardiovascular dysfunction in animals subjected to 6-OHDA Parkinsonism may be peripheral and involve the participation of endothelial iNOS.

Nitric Oxide Involvement in Cardiovascular Dysfunctions of Parkinson Disease

Parkinson’s disease (PD) is characterized by the loss of dopaminergic neurons in the substantia nigra, causing motor changes. In addition to motor symptoms, non-motor dysfunctions such as psychological, sensory and autonomic disorders are recorded. Manifestations related to the autonomic nervous system include the cardiovascular system, as postural hypotension, postprandial hypotension, and low blood pressure. One of the mediators involved is the nitric oxide (NO). In addition to the known roles such as vasodilator, neuromodulator, NO acts as an important mediator of the immune response, increasing the inflammatory response provoked by PD in central nervous system. The use of non-specific NOS inhibitors attenuated the neurodegenerative response in animal models of PD. However, the mechanisms by which NO contributes to neurodegeneration are still not well understood. The literature suggest that the contribution of NO occurs through its interaction with superoxides, products of oxidative stress, and blocking of the mitochondrial respiratory chain, resulting in neuronal death. Most studies involving Parkinsonism models have evaluated brain NO concentrations, with little data available on its peripheral action. Considering that studies that evaluated the involvement of NO in the neurodegeneration in PD, through NOS inhibitors administration, showed neuroprotection in rats, it has prompted new studies to assess the participation of NOS isoforms in cardiovascular changes induced by parkinsonism, and thus to envision new targets for the treatment of cardiovascular disorders in PD. The aim of this study was to conduct a literature review to assess available information on the involvement of nitric oxide (NO) in cardiovascular aspects of PD.

Sleep and circadian rhythms in Parkinson's disease and preclinical models

The use of animals as models of human physiology is, and has been for many years, an indispensable tool for understanding the mechanisms of human disease. In Parkinson's disease, various mouse models form the cornerstone of these investigations. Early models were developed to reflect the traditional histological features and motor symptoms of Parkinson's disease. However, it is important that models accurately encompass important facets of the disease to allow for comprehensive mechanistic understanding and translational significance. Circadian rhythm and sleep issues are tightly correlated to Parkinson's disease, and often arise prior to the presentation of typical motor deficits. It is essential that models used to understand Parkinson's disease reflect these dysfunctions in circadian rhythms and sleep, both to facilitate investigations into mechanistic interplay between sleep and disease, and to assist in the development of circadian rhythm-facing therapeutic treatments. This review describes the extent to which various genetically- and neurotoxically-induced murine models of Parkinson's reflect the sleep and circadian abnormalities of Parkinson's disease observed in the clinic.

Cardiac Changes in Parkinson's Disease: Lessons from Clinical and Experimental Evidence

Dysautonomia is a common non-motor symptom in Parkinson's disease (PD). Most dysautonomic symptoms appear due to alterations in the peripheral nerves of the autonomic nervous system, including both the sympathetic and parasympathetic nervous systems. The degeneration of sympathetic nerve fibers and neurons leads to cardiovascular dysfunction, which is highly prevalent in PD patients. Cardiac alterations such as orthostatic hypotension, heart rate variability, modifications in cardiogram parameters and baroreflex dysfunction can appear in both the early and late stages of PD, worsening as the disease progresses. In PD patients it is generally found that parasympathetic activity is decreased, while sympathetic activity is increased. This situation gives rise to an imbalance of both tonicities which might, in turn, promote a higher risk of cardiac damage through tachycardia and vasoconstriction. Cardiovascular abnormalities can also appear as a side effect of PD treatment: L-DOPA can decrease blood pressure and aggravate orthostatic hypotension as a result of a negative inotropic effect on the heart. This unwanted side effect limits the therapeutic use of L-DOPA in geriatric patients with PD and can contribute to the number of hospital admissions. Therefore, it is essential to define the cardiac features related to PD for the monitorization of the heart condition in parkinsonian individuals. This information can allow the application of intervention strategies to improve the course of the disease and the proposition of new alternatives for its treatment to eliminate or reverse the motor and non-motor symptoms, especially in geriatric patients.

Animal models of Parkinson's disease: a guide to selecting the optimal model for your research

Parkinson's disease (PD) is a complex, multisystem disorder characterised by α-synuclein (SNCA) pathology, degeneration of nigrostriatal dopaminergic neurons, multifactorial pathogenetic mechanisms and expression of a plethora of motor and non-motor symptoms. Animal models of PD have already been instructive in helping us unravel some of these aspects. However, much remains to be discovered, requiring continued interrogation by the research community. In contrast with the situation for many neurological disorders, PD benefits from of a wide range of available animal models (pharmacological, toxin, genetic and α-synuclein) but this makes selection of the optimal one for a given study difficult. This is especially so when a study demands a model that displays a specific combination of features. While many excellent reviews of animal models already exist, this review takes a different approach with the intention of more readily informing this decision-making process. We have considered each feature of PD in turn - aetiology, pathology, pathogenesis, motor dysfunctions and non-motor symptoms (NMS) - highlighting those animal models that replicate each. By compiling easily accessible tables and a summary figure, we aim to provide the reader with a simple, go-to resource for selecting the optimal animal model of PD to suit their research needs.

Baroreflex dysfunction in Parkinson's disease: integration of central and peripheral mechanisms

The incidence of Parkinson's disease (PD) is increasing worldwide. Although the PD hallmark is the motor impairments, nonmotor dysfunctions are now becoming more recognized. Recently, studies have suggested that baroreflex dysfunction is one of the underlying mechanisms of cardiovascular dysregulation observed in patients with PD. However, the large body of literature on baroreflex function in PD is unclear. The baroreflex system plays a major role in the autonomic, and ultimately blood pressure and heart rate, adjustments that accompany acute cardiovascular stressors on a daily basis. Therefore, impaired baroreflex function (i.e., decreased sensitivity or gain) can lead to altered neural cardiovascular responses. Since PD affects parasympathetic and sympathetic branches of the autonomic nervous system and both are orchestrated by the baroreflex system, understanding of this crucial mechanism in PD is necessary. In the present review, we summarize the potential altered central and peripheral mechanisms affecting the feedback-controlled loops that comprise the reflex arc in patients with PD. Major factors including arterial stiffness, reduced number of C1 and activation of non-C1 neurons, presence of central α-synuclein aggregation, cardiac sympathetic denervation, attenuated muscle sympathetic nerve activity, and lower norepinephrine release could compromise baroreflex function in PD. Results from patients with PD and from animal models of PD provide the reader with a clearer picture of baroreflex function in this clinical condition. By doing so, our intent is to stimulate future studies to evaluate several unanswered questions in this research area.

Increased energy expenditure and activated β3-AR-cAMP-PKA signaling pathway in the interscapular brown adipose tissue of 6-OHDA-induced Parkinson's disease model rats

To explore the possible mechanism of weight loss in Parkinson's disease (PD). Bilateral injections of 6-hydroxydopamine (6-OHDA) into substantia nigra (SN) were performed to induce the PD model rats. The rotarod test, food intake, body weight, and interscapular brown adipose tissue (IBAT) weight were recorded 6 weeks postoperation. HE staining was performed to observe the morphology of multilocular adipose cells in IBAT. Immunohistochemistry and western blot were used to determine the protein levels of tyrosine hydroxylase (TH) in the SN, and the levels of uncoupling protein 1 (UCP1), peroxisome proliferator-activated receptor gamma coactivator-1α (PGC-1α), phosphorylated-hormone sensitive lipase (p-HSL), HSL, TH, β3-adrenergic receptor (β3-AR), cyclic adenosine monophosphate (cAMP), and protein kinase A (PKA) in IBAT. After treatment with 6-OHDA for 6 weeks, 6-OHDA rats exhibited decreased TH expression in SN accompanied with shortened staying time on the rotating rod. This motor impairment paralleled with no significant alteration in body mass, IBAT weight, and food intake until the end of the experimental protocol. However, the decreasing diameter of the single fat vesicle in IBAT was observed in the 6-OHDA group. Meanwhile, compared with the control group, the protein expression of UCP1, PGC-1α, p-HSL, TH, β3-AR, cAMP, and PKA in IBAT were increased significantly in the 6-OHDA group, whereas no obvious change in the expression of HSL. The present study suggested an increased energy expenditure and activation of the β3-AR-cAMP-PKA signaling pathway in the IBAT after the destruction of the dopamine system in the SN of the rat.

Cardiovascular evaluation of female rats with 6-OHDA-induced parkinsonism: Possible protection by ovarian hormones and participation of nitric oxide

AIMS

Parkinson's disease (PD) is a neurological disorder caused by environmental and genetic factors, characterized by the death of dopaminergic neurons of the substantia nigra pars compacta (SNpc), leading to a decrease of dopamine in the striatum. In addition to motor symptoms, PD has several abnormalities, among which are cardiovascular changes, such as orthostatic and postprandial hypotension, and blood pressure lability. Studies demonstrate gender differences in PD pathogenesis, indicating that female hormones have a protective role against disease development. However, no studies examining cardiovascular changes in a female rat model of parkinsonism exist.

MAIN METHODS

Wistar female rats were subjected to ovariectomy (OVX) or sham surgery. After seven days, these animals were subjected to bilateral infusion of 6-hydroxydopamine (6-OHDA) or vehicle solution in their SNpc. On the 14th experimental day, a femoral artery catheterization was performed to record cardiovascular parameters after 24 h in conscious state. Analyses of cardiovascular variability and spontaneous baroreflex were performed. The nitrite (NO) concentration in the heart, thoracic aorta, abdominal aorta, and plasma was measured.

KEY FINDINGS

The sham-6-OHDA group had no decrease in the mean arterial pressure compared to sham-saline group, whereas the OVX-6-OHDA group presented a baseline decrease in comparison to sham-6-OHDA. The OVX-6-OHDA group showed an NO increase in the heart and abdominal aorta, whereas the sham-6-OHDA group did not. The very low frequency variability component decreased in the sham-6-OHDA but not in the OVX-6-OHDA group.

SIGNIFICANCE

We suggest a cardiovascular protection by ovarian hormones in PD with a possible NO involvement.

L. L. Pinheiro D, de la Rosa T, G. de Almeida AC, A. Scorza F, A. Scorza C. Propolis as A Potential Disease-Modifying Strategy in Parkinson's Disease: Cardioprotective and Neuroprotective Effects in the 6-OHDA Rat Model

Patients with Parkinson's disease (PD) manifest nonmotor and motor symptoms. Autonomic cardiovascular dysregulation is a common nonmotor manifestation associated with increased morbimortality. Conventional clinical treatment alleviates motor signs but does not change disease progression and fails in handling nonmotor features. Nutrition is a key modifiable determinant of chronic disease. This study aimed to assess the effects of propolis on cardiological features, heart rate (HR) and heart rate variability (HRV) and on nigrostriatal dopaminergic damage, detected by tyrosine hydroxylase (TH) immunoreactivity, in the 6-hydroxydopamine (6-OHDA) rat model of PD. Male Wistar rats were injected bilaterally with 6-OHDA or saline into the striatum and were treated with propolis or water for 40 days. Autonomic function was assessed by time domain parameters (standard deviation of all normal-to-normal intervals (SDNN) and square root of the mean of the squared differences between adjacent normal RR intervals (RMSSD)) of HRV calculated from electrocardiogram recordings. Reductions in HR (p = 1.47×10-19), SDNN (p = 3.42×10-10) and RMSSD (p = 8.2×10-6) detected in parkinsonian rats were reverted by propolis. Propolis attenuated neuronal loss in the substantia nigra (p = 5.66×10-15) and reduced striatal fiber degeneration (p = 7.4×10-5) in 6-OHDA-injured rats, which also showed significant weight gain (p = 1.07×10-5) in comparison to 6-OHDA-lesioned counterparts. Propolis confers cardioprotection and neuroprotection in the 6-OHDA rat model of PD.

Assessment of vitamin D and inflammatory markers profile in cardiac tissue on Parkinson disease animal model

BACKGROUND

Cardiovascular dysfunctions are common non-motor symptoms in patients with Parkinson's disease (PD) that can result in reduced quality of life and even death. Research in animal models designed to characterize the pathological association between PD and cardiovascular abnormalities is still in its infancy. This study assessed the early impact of the nigrostriatal dopaminergic damage on cardiological features in the unilateral 6-OHDA rat model of PD.

METHODS

Male Wistar rats received unilateral intrastriatal injections of 6-OHDA and sham rats were injected with saline. Animals were studied 15 days later. Immunohistochemistry was used for visualization of tyrosine hydroxylase (TH)-positive neurons in the nigrostriatal system. Electrocardiogram recordings of heart rate were performed in conscious rats. Heart levels of vitamin D, inflammatory cytokines and C-reactive protein were assessed through electrochemiluminescence immunoassay, quantitative reverse transcription PCR and turbidimetric method, respectively.

RESULTS

We found a post-injury reduction of TH-immunoreactivity of approximately 45% in the substantia nigra pars compacta and 20% in the striatum. Heart rate reduction was found in 6-OHDA-lesioned rats as compared with sham counterparts. Reduced levels of vitamin D and increased levels of inflammatory factors (C-reactive protein, IL-6, TNF-α and TGF-β) were detected in the heart tissue of PD rats in comparison with sham.

CONCLUSION

Our findings suggest a link between cardiac tissue changes and cardiac functional changes early after the central dopaminergic damage induced by 6-OHDA. Knowledge of the cardiac abnormalities in the 6-OHDA model is critical in identifying future therapeutic targets and disease-modifying approaches for PD non-motor features.

Glutamate and GABA neurotransmission are increased in paraventricular nucleus of hypothalamus in rats induced to 6-OHDA parkinsonism: Involvement of nNOS

AIM

Parkinson's disease (PD) is a progressive neurodegenerative disease that manifests itself clinically after reaching an advanced pathological stage. Besides motor signals, PD patients present cardiovascular and autonomic alterations. Recent data showed that rats induced to Parkinsonism by 6-hydroxydopamine (6-OHDA) administration in the substantia nigra pars compacta (SNpc) showed lower mean arterial pressure (MAP) and heart rate (HR), as reduction in sympathetic modulation. The paraventricular nucleus of the hypothalamus (PVN) is an important site for autonomic and cardiovascular control, and amino acid neurotransmission has a central role. We evaluate PVN amino acid neurotransmission in cardiovascular and autonomic effects of 6-OHDA Parkinsonism.

METHODS

Male Wistar rats were submitted to guide cannulas implantation into the PVN. 6-OHDA or sterile saline (sham) was administered bilaterally in the SNpc. After 7 days, cardiovascular recordings in conscious state was performed.

RESULTS

Bicuculline promoted an increase in MAP and HR in sham group and exacerbated those effects in 6-OHDA group. NBQX (non-NMDA inhibitor) did not promote changes in sham as in 6-OHDA group. On the other hand, PVN microinjection of LY235959 (NMDA inhibitor) in sham group did not induced cardiovascular alterations, but decreased MAP and HR in 6-OHDA group. Compared to Sham group, 6-OHDA lesion increased the number of neuronal nitric oxide synthase (nNOS)-immunoreactive neurons in the PVN and, nNOS inhibition promoted higher increases in MAP and HR.

CONCLUSION

Our data suggest that the decreased baseline blood pressure and heart rate in animals with Parkinsonism may be due to an increased GABAergic tone via nNOS in the PVN.

Repeated social defeat induces transient glial activation and brain hypometabolism: A positron emission tomography imaging study

Psychosocial stress is a risk factor for the development of depression. Recent evidence suggests that glial activation could contribute to the development of depressive-like behaviour. This study aimed to evaluate in vivo whether repeated social defeat (RSD) induces short- and long-term inflammatory and metabolic alterations in the brain through positron emission tomography (PET). Male Wistar rats ( n = 40) were exposed to RSD by dominant Long-Evans rats on five consecutive days. Behavioural and biochemical alterations were assessed at baseline, day 5/6 and day 24/25 after the RSD protocol. Glial activation (11C-PK11195 PET) and changes in brain metabolism (18F-FDG PET) were evaluated on day 6, 11 and 25 (short-term), and at 3 and 6 months (long-term). Defeated rats showed transient depressive- and anxiety-like behaviour, increased corticosterone and brain IL-1β levels, as well as glial activation and brain hypometabolism in the first month after RSD. During the third- and six-month follow-up, no between-group differences in any investigated parameter were found. Therefore, non-invasive PET imaging demonstrated that RSD induces transient glial activation and reduces brain glucose metabolism in rats. These imaging findings were associated with stress-induced behavioural changes and support the hypothesis that neuroinflammation could be a contributing factor in the development of depression.

Potential Application of Yokukansan as a Remedy for Parkinson’s Disease

Parkinson’s disease (PD), the second most common progressive neurodegenerative disorder, is characterized by complex motor and nonmotor symptoms. The clinical diagnosis of PD is defined by bradykinesia and other cardinal motor features, although several nonmotor symptoms are also related to disability, an impaired quality of life, and shortened life expectancy. Levodopa, which is used as a standard pharmacotherapy for PD, has limitations including a short half-life, fluctuations in efficacy, and dyskinesias with long-term use. There have been efforts to develop complementary and alternative therapies for incurable PD. Yokukansan (YKS) is a traditional herbal medicine that is widely used for treating neurosis, insomnia, and night crying in children. The clinical efficacy of YKS for treating behavioral and psychological symptoms, such as delusions, hallucinations, and impaired agitation/aggression subscale and activities of daily living scores, has mainly been investigated in the context of neurological disorders such as PD, Alzheimer’s disease, and other psychiatric disorders. Furthermore, YKS has previously been found to improve clinical symptoms, such as sleep disturbances, neuropsychiatric and cognitive impairments, pain, and tardive dyskinesia. Preclinical studies have reported that the broad efficacy of YKS for various symptoms involves its regulation of neurotransmitters including GABA, serotonin, glutamate, and dopamine, as well as the expression of dynamin and glutamate transporters, and changes in glucocorticoid hormones and enzymes such as choline acetyltransferase and acetylcholinesterase. Moreover, YKS has neuroprotective effects at various cellular levels via diverse mechanisms. In this review, we focus on the clinical efficacy and neuropharmacological effects of YKS. We discuss the possible mechanisms underpinning the effects of YKS on neuropathology and suggest that the multiple actions of YKS may be beneficial as a treatment for PD. We highlight the potential that YKS may serve as a complementary and alternative strategy for the treatment of PD.

Potential Application of Yokukansan as a Remedy for Parkinson's Disease

Parkinson's disease (PD), the second most common progressive neurodegenerative disorder, is characterized by complex motor and nonmotor symptoms. The clinical diagnosis of PD is defined by bradykinesia and other cardinal motor features, although several nonmotor symptoms are also related to disability, an impaired quality of life, and shortened life expectancy. Levodopa, which is used as a standard pharmacotherapy for PD, has limitations including a short half-life, fluctuations in efficacy, and dyskinesias with long-term use. There have been efforts to develop complementary and alternative therapies for incurable PD. Yokukansan (YKS) is a traditional herbal medicine that is widely used for treating neurosis, insomnia, and night crying in children. The clinical efficacy of YKS for treating behavioral and psychological symptoms, such as delusions, hallucinations, and impaired agitation/aggression subscale and activities of daily living scores, has mainly been investigated in the context of neurological disorders such as PD, Alzheimer's disease, and other psychiatric disorders. Furthermore, YKS has previously been found to improve clinical symptoms, such as sleep disturbances, neuropsychiatric and cognitive impairments, pain, and tardive dyskinesia. Preclinical studies have reported that the broad efficacy of YKS for various symptoms involves its regulation of neurotransmitters including GABA, serotonin, glutamate, and dopamine, as well as the expression of dynamin and glutamate transporters, and changes in glucocorticoid hormones and enzymes such as choline acetyltransferase and acetylcholinesterase. Moreover, YKS has neuroprotective effects at various cellular levels via diverse mechanisms. In this review, we focus on the clinical efficacy and neuropharmacological effects of YKS. We discuss the possible mechanisms underpinning the effects of YKS on neuropathology and suggest that the multiple actions of YKS may be beneficial as a treatment for PD. We highlight the potential that YKS may serve as a complementary and alternative strategy for the treatment of PD.

Effects of Inducible Nitric Oxide Synthase Inhibition on Cardiovascular Risk of Adult Endotoxemic Female Rats: Role of Estrogen

Aim: Autonomic modulation responds to ovarian hormones and estrogen increases nitric oxide bioavailability. Also, females have minor susceptibility to sepsis and a higher survival rate. However, few studies have evaluated the role of estrogen in cardiovascular, autonomic, and oxidative parameters during initial endotoxemia and under inducible nitric oxide synthase (iNOS) inhibition in female rats.

Methods: Female wistar rats were subjected to ovariectomy and divided into three groups: OVX (ovariectomized), OVX+E (OVX plus daily estradiol) and SHAM (false surgery). After 8 weeks, mean arterial pressure (MAP) and heart rate (HR) were recorded in non-anesthetized catheterized rats, before and after intravenous LPS injection, preceded by S-methylisothiourea sulfate (SMT) injection, or sterile saline. Cardiovascular recordings underwent spectral analysis for evaluation of autonomic modulation. Two hours after LPS, plasma was collected to assess total radical-trapping antioxidant (TRAP), nitrite levels (NO2), lipoperoxidation (LOOH), and paraoxonase 1 (PON1) activity.

Results: Two hours after LPS, females treated with SMT presented a decrease of MAP, when compared to saline-LPS groups. At this same time, all SMT+LPS groups presented an increase of sympathetic and a decrease of parasympathetic modulation of HR. Two hours after saline+LPS, OVX presented decreased total radical-trapping antioxidant (TRAP) compared to SHAM. When treated with SMT+LPS, OVX did not altered TRAP, while estradiol reduced LOOH levels.

Conclusion: iNOS would be responsible for sympathetic inhibition and consumption of antioxidant reserves of females during endotoxemia, since iNOS is inhibited, treatment with estradiol could be protective in inflammatory challenges.

[Autoregulation of cerebral blood flow in severe diffuse axonal brain injury: the role of neuroanatomical factors]

Autoregulation of cerebral blood flow (ACBF) is a system of mechanisms for maintaining stable adequate perfusion of the brain despite changes in systemic arterial pressure. In recent years, new data on the numerous metabolic and systemic mechanisms of cerebral blood flow regulation have been obtained, but the role of neurogenic regulation has not yet been fully understood and, therefore, not considered in clinical practice.

AIM

The study aim was to assess the effect of anatomical injuries to deep brain structures on the extent and duration of ACBF abnormalities in a model of severe diffuse axonal injury (DAI).

RESULTS

The study demonstrated that brain injury in the projection of a dopaminergic structure (substantia nigra) and a cholinergic structure (nucleus basalis of Meynert region) was more common in patients with impaired ACBF and was associated with a longer duration of the impairment.

CONCLUSION

The obtained data may indicate the presence of central (neurogenic) pathways of cerebral vessel tone regulation; traumatic injury of the pathways leads to a more severe and prolonged period of impaired ACBF. Probably, injury to these regulatory structures in some patients has an indirect effect on the course of intracranial hypertension. Further experimental and clinical studies in this direction are needed to elucidate all elements of neurogenic regulation of cerebral vessel tone and ACBF mechanisms.

Short- and long-term effects induced by repeated 6-OHDA intraventricular administration: A new progressive and bilateral rodent model of Parkinson's disease

The pathological hallmark of Parkinson's disease (PD) is the progressive degeneration of dopaminergic neurons in the substantia nigra pars compacta (SNpc), and the resulting striatal dopamine deficiency, which are responsible for the classic motor features. Although a diagnosis of PD relies on the clinical effects of dopamine deficiency, this disease is also associated with other neurotransmitter deficits that are recognized as causing various motor and non-motor symptoms. However, the cause of dopaminergic nigral neurodegeneration in PD and the underlying mechanisms remain unknown. While animal models are considered valuable tools with which to investigate dopaminergic cell vulnerability, rodent models usually fail to mimic the neurodegeneration progression that occurs in human PD. To find a convenient rat model for studying the progression of dopaminergic cell degeneration and motor signs, we have developed a progressive rodent model using a repeated daily, intraventricular administration of the neurotoxin 6-hydroxydopamine (6-OHDA) (100µg/day) in awakened rats for 1 to 10 consecutive days. The short- (6-day) and long-term (32-day) progression of motor alterations was studied. This model leads to a bilateral and progressive increase in catalepsy (evident from the 3rd infusion in the short-term groups (p<0.01) and from the 7th infusion in the long-term groups (p<0.01), which was associated with a progressive nigrostriatal dopaminergic deficit. All together this makes the new model an interesting experimental tool to investigate the mechanisms involved in the progression of dopaminergic neurodegeneration.

Nonmotor Symptoms in Experimental Models of Parkinson's Disease

Nonmotor symptoms of Parkinson's disease (PD) range from neuropsychiatric, cognitive to sleep and sensory disorders and can arise from the disease process as well as from drug treatment. The clinical heterogeneity of nonmotor symptoms of PD is underpinned by a wide range of neuropathological and molecular pathology, affecting almost the entire range of neurotransmitters present in brain and the periphery. Understanding the neurobiology and pathology of nonmotor symptoms is crucial to the effective treatment of PD and currently a key unmet need. This bench-to-bedside translational concept can only be successful if robust animal models of PD charting the genesis and natural history of nonmotor symptoms can be devised. Toxin-based and transgenic rodent and primate models of PD have given us important clues to the underlying basis of motor symptomatology and in addition, can provide a snapshot of some nonmotor aspects of PD, although the data are far from complete. In this chapter, we discuss some of the nonmotor aspects of the available experimental models of PD and how the development of robust animal models to understand and treat nonmotor symptoms needs to become a research priority.

Non-motor features of Parkinson disease

Many of the motor symptoms of Parkinson disease (PD) can be preceded, sometimes for several years, by non-motor symptoms that include hyposmia, sleep disorders, depression and constipation. These non-motor features appear across the spectrum of patients with PD, including individuals with genetic causes of PD. The neuroanatomical and neuropharmacological bases of non-motor abnormalities in PD remain largely undefined. Here, we discuss recent advances that have helped to establish the presence, severity and effect on the quality of life of non-motor symptoms in PD, and the neuroanatomical and neuropharmacological mechanisms involved. We also discuss the potential for the non-motor features to define a prodrome that may enable the early diagnosis of PD.

Baroreflex control of renal sympathetic nerve activity in early heart failure assessed by the sequence method

KEY POINTS

The integrity of the baroreflex control of sympathetic activity in heart failure (HF) remains under debate. We proposed the use of the sequence method to assess the baroreflex control of renal sympathetic nerve activity (RSNA). The sequence method assesses the spontaneous arterial pressure (AP) fluctuations and their related changes in heart rate (or other efferent responses), providing the sensitivity and the effectiveness of the baroreflex. Effectiveness refers to the fraction of spontaneous AP changes that elicits baroreflex-mediated variations in the efferent response. Using three different approaches, we showed that the baroreflex sensitivity between AP and RSNA is not altered in early HF rats. However, the sequence method provided evidence that the effectiveness of baroreflex in changing RSNA in response to AP changes is markedly decreased in HF. The results help us better understand the baroreflex control of the sympathetic nerve activity.

ABSTRACT

In heart failure (HF), the reflex control of the heart rate is known to be markedly impaired; however, the baroreceptor control of the sympathetic drive remains under debate. Applying the sequence method to a series of arterial pressure (AP) and renal sympathetic nerve activity (RSNA), we demonstrated a clear dysfunction in the baroreflex control of sympathetic activity in rats with early HF. We analysed the baroreflex control of the sympathetic drive using three different approaches: AP vs. RSNA curve, cross-spectral analysis and sequence method between AP and RSNA. The sequence method also provides the baroreflex effectiveness index (BEI), which represents the percentage of AP ramps that actually produce a reflex response. The methods were applied to control rats and rats with HF induced by myocardial infarction. None of the methods employed to assess the sympathetic baroreflex gain were able to detect any differences between the control and the HF group. However, rats with HF exhibited a lower BEI compared to the controls. Moreover, an optimum delay of 1 beat was observed, i.e. 1 beat is required for the RSNA to respond after AP changing, which corroborates with the findings related to the timing between these two variables. For delay 1, the BEI of the controls was 0.45 ± 0.03, whereas the BEI of rats with HF was 0.29 ± 0.09 (P < 0.05). These data demonstrate that while the gain of the baroreflex is not affected in early HF, its effectiveness is markedly decreased. The analysis of the spontaneous changes in AP and RSNA using the sequence method provides novel insights into arterial baroreceptor reflex function.

Contribution of the nitric oxide donor molsidomine and the antiparkinsonian drug l-DOPA to the modulation of the blood pressure in unilaterally 6-OHDA-lesioned rats

BACKGROUND

Interaction between dopaminergic and nitrergic neurotransmission in the brain plays a crucial role in the control of motor function and in the regulation of blood pressure (BP). In Parkinson's disease (PD), dopaminergic denervation of the striatum leads to disturbances in the nitrergic system in the basal ganglia. Recently, it has been demonstrated that addition of a low dose of the nitric oxide donor molsidomine to l-DOPA therapy improves dopaminergic neurotransmission in the denervated nigrostriatal system and weakens dyskinesias in rodent models of the disease.

METHODS

The aim of the present study was to examine the impact of chronic administration of molsidomine (2mg/kg) and l-DOPA (25mg/kg), alone and in combination, on systolic (SBP) and diastolic (DBP) blood pressure in the anesthetized, unilaterally 6-OHDA-lesioned rats. The measurement of SBP and DBP was performed 24h after the penultimate and immediately after the last drug doses.

RESULTS

In 6-OHDA-lesioned rats receiving saline, spontaneous, small decreases in SBP and DBP were observed during the measurements lasting 60min. Administration of molsidomine alone or in combination with l-DOPA distinctly decreased the BP in 6-OHDA-lesioned rats already after 10min compared to those treated with saline or l-DOPA alone, respectively. In both groups, the molsidomine-mediated declines in BP persisted till the end of measurement but they disappeared after 24h.

CONCLUSIONS

Our results indicate that in this PD model molsidomine evokes a short-lasting decrease in BP in contrast to conventional antihypertensive drugs that maintain long-term effect and worsen orthostatic hypotension in parkinsonian patients.

Lesion of medullary catecholaminergic neurons is associated with cardiovascular dysfunction in rotenone-induced Parkinson's disease rats

In recent years, non-motor symptoms have been recognised as of vital importance in Parkinson's disease (PD); among these, cardiovascular dysfunctions are commonly seen in PD patients before their motor signs. The role of cardiovascular dysfunction in the progression of PD pathology, and its underlying mechanisms, are largely unknown. In the present study, in rotenone-induced PD rats, there was a gradual reduction in the number of nigral tyrosine hydroxylase-immunoreactive (TH-ir) neurons after 7, 14 and 21 days treatment. With the 56% reduction in striatal dopamine content and 52% loss of TH-ir neurons on the 14th day, the rats showed motor dysfunctions. However, from ECG power spectra, reductions in normalised low-frequency power and in the low-frequency power : high-frequency power ratio, as well as in mean blood pressure, were observed as early as the 3rd day. Plasma norepinephrine (NE) and epinephrine (E) levels were decreased by 39% and 26% respectively at the same time. Pearson's correlation analysis showed that both plasma NE and plasma E levels were positively correlated with MBP. Our results also showed that the loss of catecholaminergic neurons in the rostral ventrolateral medulla (RVLM), but not in the caudal ventrolateral medulla or the nucleus tractus solitarii, emerged earlier than the loss of nigral dopaminergic neurons. This suggests that dysfunction of catecholaminergic neurons in the RVLM might account for the reduced sympathetic activity, MBP and plasma catecholamine levels in the early stages of PD.