The hypothalamus in Parkinson disease

An overview of the effects of levodopa and dopaminergic agonists on sleep disorders in Parkinson's disease

Sleep disorders are among the most common nonmotor symptoms in Parkinson's disease and are associated with reduced cognition and health-related quality of life. Disturbed sleep can often present in the prodromal or early stages of this neurodegenerative disease, rendering it crucial to manage and treat these symptoms. Levodopa and dopaminergic agonists are frequently prescribed to treat motor symptoms in Parkinson's disease, and there is increasing interest in how these pharmacological agents affect sleep and their effect on concomitant sleep disturbances and disorders. In this review, we discuss the role of dopamine in regulating the sleep-wake state and the impact of neurodegeneration on sleep. We provide an overview of the effects of levodopa and dopaminergic agonists on sleep architecture, insomnia, excessive daytime sleepiness, sleep-disordered breathing, rapid eye movement sleep behavior disorder, and restless legs syndrome in Parkinson's disease. Levodopa and dopaminergic drugs may have different effects, beneficial or adverse, depending on dosing, method of administration, and differential effects on the different dopamine receptors. Future research in this area should focus on elucidating the specific mechanisms by which these drugs affect sleep in order to better understand the pathophysiology of sleep disorders in Parkinson's disease and aid in developing suitable therapies and treatment regimens.

CITATION

Scanga A, Lafontaine A-L, Kaminska M. An overview of the effects of levodopa and dopaminergic agonists on sleep disorders in Parkinson's disease. J Clin Sleep Med. 2023;19(6):1133-1144.

Potential Crosstalk Between Parkinson's Disease and Energy Metabolism

Parkinson's disease (PD) is characterized by the accumulation of alpha-synuclein (α-Syn) in the substantia nigra (SN) and the degeneration of nigrostriatal dopaminergic (DAergic) neurons. Some studies have reported that the pathology of PD originates from the gastrointestinal (GI) tract, which also serves as an energy portal, and develops upward along the neural pathway to the central nervous system (CNS), including the dorsal motor nucleus of vagus (DMV), SN, and hypothalamus, which are also involved in energy metabolism control. Therefore, we discuss the alterations of nuclei that regulate energy metabolism in the development of PD. In addition, due to their anti-inflammatory, antiapoptotic and antioxidative roles, metabolism-related peptides are involved in the progression of PD. Furthermore, abnormal glucose and lipid metabolism are common in PD patients and exacerbate the pathological changes in PD. Therefore, in this review, we attempt to explain the correlation between PD and energy metabolism, which may provide possible strategies for PD treatment.

Orexin and Parkinson's disease: A protective neuropeptide with therapeutic potential

Parkinson's disease (PD) is the second most common neurodegenerative disease caused by the progressive loss of dopaminergic neurons in the substantia nigra pars compacta. PD is characterized by motor dysfunctions as well as non-motor disorders. Orexin (also known as hypocretin) is a kind of neuropeptide involved in the regulation of motor control, the sleep/wake cycle, learning and memory, gastric motility and respiratory function. Several lines of evidence suggest that the orexinergic system is involved in the manifestations of PD, especially the non-motor disorders. Recent studies have revealed the protective actions and potential therapeutic applications of orexin in both cellular and animal models of PD. Here we present a brief overview of the involvement of the orexinergic system in PD, including the pathological changes in the lateral hypothalamus, the loss of orexinergic neurons and the fluctuation of orexin levels in CSF. Furthermore, we also review the neuroprotective effects of orexin in cellular and animal models of PD.

Autonomic dysfunction in Parkinson disease and animal models

Parkinson disease has traditionally been classified as a movement disorder, despite patients' accounts of diverse symptoms stemming from impairments in numerous body systems. Today, Parkinson disease is increasingly recognized by clinicians and scientists as a complex neurodegenerative disorder featuring both motor and nonmotor manifestations concomitant with pathology throughout all major branches of the nervous system. Dysfunction of the autonomic nervous system, or dysautonomia, is a common feature of Parkinson disease. It produces signs and symptoms that severely affect patients' quality of life, such as blood pressure dysregulation, hyperhidrosis, and constipation. Treatment options for dysautonomia are limited to symptom alleviation because the cause of these symptoms and Parkinson disease overall are still unknown. Animal models provide a platform to interrogate mechanisms of Parkinson disease-related autonomic nervous system dysfunction and test novel treatment strategies. Several animal models of Parkinson disease are available, each with different effects on the autonomic nervous system. This review critically analyses key dysautonomia signs and symptoms and associated pathology in Parkinson disease patients and relevant findings in animal models. We focus on the cardiovascular system, adrenal medulla, skin/thermoregulation, bladder, pupils, and gastrointestinal tract, to assess the contribution of animal models to the understanding of Parkinson disease autonomic dysfunction.

Biomarkers for Parkinson's Disease: Recent Advancement

As a multi-factorial degenerative disease, Parkinson's disease (PD) leads to tremor, gait rigidity, and hypokinesia, thus hampering normal living. As this disease is usually detected in the later stages when neurons have degenerated completely, cure is on hold, ultimately leading to death due to the lack of early diagnostic techniques. Thus, biomarkers are required to detect the disease in the early stages when prevention is possible. Various biomarkers providing early diagnosis of the disease include those of imaging, cerebrospinal fluid, oxidative stress, neuroprotection, and inflammation. Also, biomarkers, alone or in combination, are used in the diagnosis and evolution of PD. This review encompasses various biomarkers available for PD and discusses recent advances in their development.

Multifactorial sleep disturbance in Parkinson's disease

Parkinson's disease (PD) is the second most common neurodegenerative disorder, ranking only behind Alzheimer's disease and affecting 2% of the population over the age of 65. Pathophysiologically, PD is characterized by selective degeneration of the dopaminergic neurons of the substantia nigra pars compacta (SNpc) and striatal dopamine depletion. Patients may also exhibit mild-to-severe degeneration of other central and peripheral nervous tissues. The most dramatic symptoms of the disease are profound dopamine-responsive motor disturbances, including bradykinesia, akinesia, rigidity, resting tremor, and postural instability. PD patients commonly present with debilitating non-motor symptoms, including cognitive impairment, autonomic nervous system dysfunction, and sleep disturbance. Of these, sleep disturbance is the most consistently reported, and likely represents a disorder integrative of PD-related motor impairment, autonomic nervous system dysfunction, iatrogenic insult, and central neurodegeneration. The pathophysiology of PD may also indirectly disrupt sleep by increasing susceptibility to sleep disorders, including sleep disordered breathing, periodic limb movements, and REM behavior disorder. In this review, we will discuss these systems representing a multifactorial etiology in PD sleep disturbance.

Neuroanatomical changes in Parkinson's disease in relation to cognition: An update

The pathophysiological changes underlying impairment of cognition in Parkinson's disease (PD) are complex and not fully understood till date. Hence, understanding the structural changes responsible for cognitive decline in PD is essential for early diagnosis and to offer effective treatment. In this review, we discuss the neuroanatomical changes in major brain structures responsible for cognition in PD. We have included the key findings of various studies to provide up-to-date information for better understanding of pathophysiology of PD, which will help researchers and clinicians in planning and developing new treatment methods for the benefit of PD patients.

Reversible Pharmacological Induction of Motor Symptoms in MPTP-Treated Mice at the Presymptomatic Stage of Parkinsonism: Potential Use for Early Diagnosis of Parkinson's Disease

A crucial event in the pathogenesis of Parkinson's disease is the death of dopaminergic neurons of the nigrostriatal system, which are responsible for the regulation of motor function. Motor symptoms first appear in patients 20-30 years after the onset of the neurodegeneration, when there has been a loss of an essential number of neurons and depletion of compensatory reserves of the brain, which explains the low efficiency of treatment. Therefore, the development of a technology for the diagnosing of Parkinson's disease at the preclinical stage is of a high priority in neurology. In this study, we have developed at an experimental model a fundamentally novel for neurology approach for diagnosis of Parkinson's disease at the preclinical stage. This methodology, widely used for the diagnosis of chronic diseases in the internal medicine, is based on the application of a challenge test that temporarily increases the latent failure of a specific functional system, thereby inducing the short-term appearance of clinical symptoms. The provocation test was developed by a systemic administration of α-methyl-p-tyrosine (αMpT), a reversible inhibitor of tyrosine hydroxylase to MPTP-treated mice at the presymptomatic stage of parkinsonism. For this, we first selected a minimum dose of αMpT, which caused a decrease of the dopamine level in the striatum of normal mice below the threshold at which motor dysfunctions appear. Then, we found the maximum dose of αMpT at which a loss of dopamine in the striatum of normal mice did not reach the threshold level, and motor behavior was not impaired. We showed that αMpT at this dose induced a decrease of the dopamine concentration in the striatum of MPTP-treated mice at the presymptomatic stage of parkinsonism below a threshold level that results in the impairment of motor behavior. Finally, we proved that αMpT exerts a temporal and reversible influence on the nigrostriatal dopaminergic system of MPTP-treated mice with no long-term side effects on other catecholaminergic systems. Thus, the above experimental data strongly suggest that αMpT-based challenge test might be considered as the provocation test for Parkinson's disease diagnosis at the preclinical stage in the future clinical trials.

[Development of preclinical diagnosis and preventive treatment of neurodegenerative diseases]

Neurodegenerative diseases (NDD) are serious fatal neurological and mental diseases that resulted in disability and fethal outcome. Based on the advances of basic sciences over the last two decades, new knowledge on the risk factors for NDD and molecular mechanisms of the pathogenesis are obtained. It has been shown that the accelerated process of neuronal death which is the main cause of NDD development begins long before the appearance of clinical symptoms. The first symptoms appeared only after the death of most specific regulatory neurons and exhaustion of brain compensatory reserve. Only at that time, one can make the diagnosis and start traditional treatment of patients that accounts for the extremely low efficacy of the latter. Currently, complex preclinical diagnosis based on the identification of relatively specific clinical precursors and peripheral biomarkers has been developing. Development of preclinical diagnosis and preventive treatment is a strategic issue of modern neurology and psychiatry. The resolution of this issue allows to consider NDD as cured, but not fatal, diseases.

Comparison of the structure, function and autophagic maintenance of mitochondria in nigrostriatal and tuberoinfundibular dopamine neurons

A pathological hallmark of Parkinson׳s disease (PD) is progressive degeneration of nigrostriatal dopamine (NSDA) neurons, which underlies the motor symptoms of PD. While there is severe loss of midbrain NSDA neurons, tuberoinfundibular (TI) DA neurons in the mediobasal hypothalamus (MBH) remain intact. In the present study, confocal microscopic analysis revealed that mitochondrial content and numbers of mitophagosomes were lower in NSDA neuronal cell bodies in the substantia nigra pars compacta (SNpc) compared to TIDA neuronal cell bodies in the arcuate nucleus (ARC) of C57BL/6J male mice. Mitochondrial respiration, mass, membrane potential and morphology were determined using bioenergetic, flow cytometric and transmission electron microscopic analyses of synaptosomes isolated from discrete brain regions containing axon terminals of NSDA and TIDA neurons. Maximum and spare respiratory capacities, and mitochondrial mass were lower in synaptosomal mitochondria derived from the striatum (ST) as compared with the MBH, which correlated with lower numbers of mitochondria per synaptosome in these brain regions. In contrast, there was no regional difference in mitochondrial basal, maximum or spare respirations following inhibition of Complex I activity with rotenone. These results reveal that higher numbers of viable mitochondria are correlated with more extensive autophagic mitochondrial quality maintenance in TIDA neurons as compared with NSDA neurons.

Effect of a single neonatal oxytocin treatment (hormonal imprinting) on the biogenic amine level of the adult rat brain: could oxytocin-induced labor cause pervasive developmental diseases?

Perinatal single-hormone treatment causes hormonal imprinting with lifelong consequences in receptor-binding capacity, hormone production as well as in social and sexual behavior. In the present experiments, newborn rats were treated with a single dose of oxytocin, and the levels of biogenic amines and their metabolites were studied in 8 different brain regions and in the sera when the male and female animals were 4 months old. Both dopaminergic and serotonergic neurotransmission was found to be significantly influenced. The levels of 3,4-dihydroxyphenylacetic acid, homovanillic acid, and 5-hydroxyindole acetic acid metabolites decreased in the hypothalamus and striatum. Dopamine, serotonin, norepinephrine, and 5-hydroxytryptophol levels were hardly altered, and there was no difference in the epinephrine levels. The results show that dopamine and serotonin metabolism of hypothalamus and striatum are deeply and lifelong influenced by a single neonatal oxytocin treatment Oxytocin imprinting resulted in decreased dopamine turnover in the hypothalamus and decreased serotonin turnover in the hypothalamus, medulla oblongata, and striatum of females. As the disturbance of brain dopamine and serotonin system has an important role in the development of pervasive developmental diseases (eg, autism) and neuropsychiatric disorders (eg, schizophrenia), the growing number of oxytocin-induced labor as a causal factor, cannot be omitted.

Time course and progression of wild type α-synuclein accumulation in a transgenic mouse model

Background

Progressive accumulation of α-synuclein (α-Syn) protein in different brain regions is a hallmark of synucleinopathic diseases, such as Parkinson’s disease, dementia with Lewy bodies and multiple system atrophy. α-Syn transgenic mouse models have been developed to investigate the effects of α-Syn accumulation on behavioral deficits and neuropathology. However, the onset and progression of pathology in α-Syn transgenic mice have not been fully characterized. For this purpose we investigated the time course of behavioral deficits and neuropathology in PDGF-β human wild type α-Syn transgenic mice (D-Line) between 3 and 12 months of age.

Results

These mice showed progressive impairment of motor coordination of the limbs that resulted in significant differences compared to non-transgenic littermates at 9 and 12 months of age. Biochemical and immunohistological analyses revealed constantly increasing levels of human α-Syn in different brain areas. Human α-Syn was expressed particularly in somata and neurites of a subset of neocortical and limbic system neurons. Most of these neurons showed immunoreactivity for phosphorylated human α-Syn confined to nuclei and perinuclear cytoplasm. Analyses of the phenotype of α-Syn expressing cells revealed strong expression in dopaminergic olfactory bulb neurons, subsets of GABAergic interneurons and glutamatergic principal cells throughout the telencephalon. We also found human α-Syn expression in immature neurons of both the ventricular zone and the rostral migratory stream, but not in the dentate gyrus.

Conclusion

The present study demonstrates that the PDGF-β α-Syn transgenic mouse model presents with early and progressive accumulation of human α-Syn that is accompanied by motor deficits. This information is essential for the design of therapeutical studies of synucleinopathies.

Progression of monoaminergic dysfunction in Parkinson's disease: a longitudinal 18F-dopa PET study

Post-mortem and neuroimaging studies in Parkinson's disease (PD) have shown involvement of the brain serotoninergic, noradrenergic and cholinergic pathways alongside the characteristic degeneration of nigrostriatal dopamine neurons. The rate of progression of the degenerative process in these extrastriatal areas is still unclear. We used (18)F-dopa PET, a marker of aromatic aminoacid decarboxylase activity in monoaminergic neurons, to assess longitudinal changes in tracer uptake in brain noradrenergic, serotoninergic and extrastriatal dopaminergic structures over a 3-year period in a group of early PD patients. Ten PD patients had (18)F-dopa PET twice: at baseline and again after 37.1±21.5 months follow up. A standard object map was used to extract tracer influx constants (Ki) in 11 striatal and extrastriatal regions. Progressive decreases in (18)F-dopa Ki occurred over the follow-up period in the majority of the investigated areas, the fastest annual declines occurring in putamen (8.1%), locus coeruleus (7.8%), and globus pallidus interna (7.7%). Caudate and hypothalamus showed 6.3% and 6.1% annual Ki declines, respectively. At baseline, some structures showed increased levels of (18)F-dopa uptake in PD compared to controls (internal pallidum, locus coeruleus), indicating possible compensatory upregulation of monoamine turnover. These increased levels had normalised (globus pallidus interna) or become subnormal (locus coeruleus) at follow-up suggesting exhaustion of these mechanisms within the first years of disease. Loss of monoaminergic function in extrastriatal regions, as reflected by(18)F-dopa PET, is delayed and occurs independently from nigrostriatal degeneration. When assessing the efficacy of novel neuroprotective agents on nigrostriatal dysfunction in PD, (18)F-dopa PET could provide supplementary information concerning function of extrastriatal monoaminergic structures.

Modeling of presymptomatic and symptomatic stages of parkinsonism in mice

A degradation of the nigrostriatal dopaminergic (DA-ergic) system is the key component of pathogenesis of Parkinson's disease (PD). Initial clinical symptoms appear 20-30 years after the onset of neurodegeneration, at a 70% DA depletion in the striatum and a 50% loss of nigral DA-ergic neurons. Low efficacy of the therapy might be improved if preclinical diagnostics and preventive therapy are developed. The development of appropriate experimental models should precede clinical trials. This multidisciplinary study first managed to model in mice with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) all together the following stages of parkinsonism: (a) the early presymptomatic stage manifested by a subthreshold degeneration of axons and DA depletion in the striatum without loss of nigral cell bodies; (b) the advanced presymptomatic stage manifested by a subthreshold degeneration of striatal axons and DA depletion and by a subthreshold loss of nigral cell bodies; (c) the advanced presymptomatic stage characterized by threshold depletion of striatal DA and a loss of DA-ergic axons and nigral cell bodies resulting in motor dysfunction. The degeneration of axons proceeds and prevails that of cell bodies suggesting higher sensitivity to MPTP of the former. Compensatory processes were developed in parallel to neurodegeneration that was manifested by the increase of the DA content in individual nigral cell bodies and DA turnover in the striatum. The developed models might be exploited for: (a) an examination of pathogenetic mechanisms not only in the nigrostriatal system but also in other brain regions and in the periphery; (b) a study of the compensatory mechanisms under DA deficiency; (c) a search of precursors of motor disorders and peripheral biomarkers in presymptomatic parkinsonism; (d) the development of preventive therapy aiming to slow down the neurodegeneration and strengthen compensatory processes. Thus, the models of the early and advanced presymptomaic stages and of the early symptomatic stage of parkinsonism were developed in mice with MPTP.

Pituitary function and the somatotrophic system in patients with idiopathic Parkinson's disease under chronic dopaminergic therapy

Idiopathic Parkinson's disease and dopaminergic medication may influence pituitary hormone secretion. The present study aimed to reveal any abnormalities of the somatotrophic system induced by the disease itself and/or the dopaminergic therapy. Investigations of other pituitary hormones under basal and stimulated conditions, as well as an analysis of body composition, were also performed. This was a controlled diagnostic study in which luteinising hormone-releasing hormone, thyroid-releasing hormone, corticotrophin-releasing hormone and arginine hydrochloride were administered to ten patients with idiopathic Parkinson's disease under dopaminergic medication. Basal and stimulated hormone concentrations and bioelectrical impedance analyses were compared with those of healthy, age-matched controls. Basal growth hormone (GH) at -30 and 0 min was higher in Parkinsonian patients (2.74 +/- 3.79 ng/ml versus 0.53 +/- 0.10 ng/ml and 2.12 +/- 2.44 ng/ml versus 0.51 +/- 0.03 ng/ml; P < 0.05). The area under the GH curve after stimulation was greater in Parkinsonian patients (502.4 +/- 202.6 ng x min/ml versus 312.0 +/- 98.5 ng x min/ml; P < 0.05), depending on higher basal GH levels, rather than a greater arginine response. No differences in insulin growth factor (IGF)-1 or IGF-BP3 concentrations were detected. There were no differences between the groups in basal and stimulated gonadotrophic, corticotrophic and thyrotrophic function, or body composition. Prolactin was below the detection limit in the patients during the course of the study. Parkinsonian patients experience marked hypoprolactinaemia and repeated stimulation of GH secretion during chronic dopaminergic therapy. Our findings suggest a peripheral GH resistance in these chronically-treated patients.

Compromised peripheral immunity of mice injected intrastriatally with six-hydroxydopamine

Intracisternal or intracerebroventricular administration of six-hydroxydopamine (6-OHDA), which results in decreased norepinephrine (NE) and dopamine (DA) levels throughout the brain, causes impaired peripheral immunity. However, in vivo immunocompetence following selective striatal depletion of DA by 6-OHDA has not been investigated. Thus, we sought to determine whether striatal DA depletion compromises host resistance to Listeria monocytogenes (LM) and impairs the immune response to keyhole limpet hemocyanin (KLH). Mice treated with 6-OHDA (90% decrease in striatal DA) had (i) increased LM colonization in liver and spleen, (ii) lower primary IgM and IgG(1) antibody titers, as well as secondary IgM titers, and (iii) compromised DTH response compared to controls. Co-administration of a DA uptake inhibitor partially (40%) spared striatal DA depletion and completely prevented the increase in LM burden, but was ineffective in preventing any of the 6-OHDA-induced suppressions of the immune responses to KLH. Thus, striatal DA is suggested to play a response-specific role in peripheral immunological functions.

Abnormal skin wrinkling in the less affected side in hemiparkinsonism-a possible test for sympathetic dysfunction in Parkinson's disease

Some patients with Parkinson's disease (PD) suffer from autonomic dysfunction, even in the early stage of the disease. We examined the skin wrinkling response following immersion of the hands in warm water in 18 patients with hemiparkinsonism. This test evaluates the function of the sympathetic autonomic system. Mean age of the patients was 61 +/- 10 and mean disease duration 5.5 +/- 3.5 years. Both hands of each patient were immersed in warm water for 30 minutes and the number of skin ridges of the fingertip of each finger was counted. The results of each hand were compared to those of nine healthy controls. The mean number of the ridges of the less affected hand was significantly decreased as compared to the affected hand and controls (6.1 +/- 6.8 vs 13.1 +/- 6.8 and 15.3 +/- 8.5, respectively; P < 0.01). These results suggest that autonomic dysfunction is prevalent in the less affected side of patients with PD and can be simply tested by the skin response test.

Treatment of Parkinson's disease with magnetic fields reduces the requirement for antiparkinsonian medications

Recently, I reported that extracranial treatment with picoTesla range magnetic fields (MF) is an effective, safe, and revolutionary modality in the management of Parkinsonism including those patients manifesting levodopa-induced motor complications. This treatment, which has emerged as a potentially more advantageous modality than pharmacologic therapy, also produces improvements in nonmotor aspects of the disease including mood, cognitive functions, sleep, pain, appetite, autonomic functions, and sexual behavior, which are usually minimally, if at all, ameliorated by long term therapy with levodopa or anticholinergic agents. The present communication concerns a 69 year old Parkinsonian patient who, following a series of two treatments with extracranial picoTesla range MF on two separate days, improved to the point where he was able to discontinue most of his antiparkinsonian medications for a period of two weeks without experiencing deterioration in symptoms. On the third week he began to develop recurrence of symptoms and resumed taking his regular medications. At the end of the fourth week the patient received a series of four magnetic treatments on four successive days after he completely discontinued his antiparkinsonian medications. During this period he experienced a remarkable improvement in motor disability as well as in cognitive functions (i.e., visuospatial performance), mood, sleep, appetite, bowel functions and resolution of pain in the lower extremity. This report attests to the antiparkinsonian efficacy of picoTesla range MF and suggests that this treatment, when applied on a regular basis, may reduce the requirement for antiparkinsonian medications. This observation, when confirmed in a larger cohort of patients, may carry important implications for the therapy of Parkinsonism as it may offer an alternative treatment for patients who develop levodopa failure or experience intolerable side effects from dopaminergic medication. The observation that magnetic treatment improved the patient's symptoms while being off dopaminergic therapy supports the role of nondopaminergic mechanisms in the pathophysiology of Parkinsonism.

Amphetamine-induced rotational behavior in rats: relationship to hypothalamic and striatal degeneration

When lesions are placed unilaterally in the nigrostriatal system of experimental animals, rotational behavior occurs in response to peripheral administration of dopamine (DA) agonists. In spite of considerable evidence to the contrary, it is assumed that in order for this rotation to occur, an almost complete depletion of striatal DA must be achieved. To test this hypothesis further, 20 male Sprague-Dawley rats were injected unilaterally with 2 microL of 8 micrograms/microL of 6-hydroxydopamine (6-OHDA) via acute injection needles or chronically indwelling cannulae. Acute injection of 6-OHDA resulted in a rotation rate of 7.2 to 18.9 revolutions per minute in response to peripheral amphetamine injection (5 mg/Kg) while injection of 6-OHDA through chronically indwelling cannulae produced rotation ranging from 1.4 to 9.9 rotations per minute. Under the conditions of either method of injection, the animals displaying the most severe rotation still showed partial denervation of striatal DA as revealed by catecholamine fluorescence histochemistry. Conversely, numerous animals demonstrating very low rates of amphetamine-induced rotation often displayed a complete loss of striatal, accumbens, and olfactory tubercle catecholamine fluorescence. Moreover, large quantities of lateral hypothalamic amine accumulation were observed in rotating rats indicating that this neurochemical change may be of functional significance for rotational responses. The present results, when taken into consideration with previous work, indicate that the routine selection of rotating animals for pharmacological testing for potential antiParkinsonian medication or intracerebral grafting purely on the basis of their rotational behavior does not necessarily imply that complete striatal denervation has occurred. Moreover, these findings demonstrate that amine accumulation in the lateral hypothalamus of rotating animals with DA depleting lesions is an important phenomenon implicated in the expression of rotational behavior in animals and possibly in the pathophysiology of Parkinson's disease.

Functional neuroanatomy and neuropathology of the human hypothalamus

The human hypothalamus is involved in a wide range of functions in the developing, adult and aging subject and is responsible for a large number of symptoms of neuroendocrine, neurological and psychiatric diseases. In the present review some prominent hypothalamic nuclei are discussed in relation to normal development, sexual differentiation, aging and a number of neuropathological conditions. The suprachiasmatic nucleus, the clock of the brain, shows seasonal and circadian variations in its vasopressin neurons. During normal aging, but even more so in Alzheimer's disease, the number of these neurons decreases. In homosexual men this nucleus is larger than in heterosexual men. The difference between the sexually dimorphic nuclei of men and women arises between the ages of 2-4 to puberty. In adult men this nucleus is twice as large as in adult women. In the process of aging, a sex-dependent decrease in cell number occurs. The vasopressin and oxytocin cells of the supraoptic and paraventricular nucleus are present in adult numbers as early as mid-gestation. Lower oxytocin neuron numbers are found in Prader-Willi syndrome, AIDS and Parkinson's disease. Familial hypothalamic diabetes insipidus is based upon a point mutation in the vasopressin-neurophysin-glycopeptide gene. Parvicellular corticotropin-releasing hormone-containing neurons in the paraventricular nucleus increase in number and are activated during the course of aging. In post-menopausal women, the infundibular or arcuate nucleus contains hypertrophic neurons containing oestrogen receptors. These neurons may be involved in the initiation of menopausal flushes. The nucleus tuberalis lateralis may be involved in feeding behaviour and metabolism. In Huntington's disease the majority of its neurons is lost; in Alzheimer's disease it shows very strong cytoskeletal alterations. Tuberomammillary nucleus neurons contain, e.g., histamine or galanine, and project to the cortex. Strong cytoskeletal changes, as well as plaques and tangles are found in this nucleus in Alzheimer's disease. The various hypothalamic nuclei are probably involved in many functions and symptoms of which only a minority has been revealed.

The relationship between diabetes mellitus and Parkinson's disease

It has been reported that 50% to 80% of patients with Parkinson's disease have abnormal glucose tolerance which may be further exacerbated by levodopa therapy. Little is known about the impact of chronic hyperglycemia on the severity of the motor manifestations and the course of the disease as well as its impact on the efficacy of levodopa or other dopaminergic drugs. This issue, which has been largely ignored, is of clinical relevance since animal studies indicate that chronic hyperglycemia decreases striatal dopaminergic transmission and increases the sensitivity of postsynaptic dopamine receptors. In addition, evidence from experimental animal studies indicates that diabetic rats are resistant to the locomotor and behavioral effects of the dopamine agonist amphetamine. The resistance to the central effects of amphetamine is largely restored with chronic insulin therapy. In the present communication, I propose that in Parkinson's disease diabetes may exacerbate the severity of the motor disability and attenuate the therapeutic efficacy of levodopa or other dopaminergic agents as well as increase the risk of levodopa-induced motor dyskinesias. Thus, it is advocated that Parkinsonian patients should be routinely screened for evidence of glucose intolerance and that if found aggressive treatment of the hyperglycemia may improve the response to levodopa and potentially diminish the risk of levodopa-induced motor dyskinesias.

Amine accumulation: a possible precursor of Lewy body formation in Parkinson's disease

It is now well recognized that the hypothalamus is an important site of neuropathology in Parkinson's disease (PD). Lewy bodies, a marker of nerve cell degeneration and a pathological hallmark of PD, have been observed frequently in the hypothalamus of PD patients by Lewy (1923) and other investigators and confirmed by more recent systematic studies by Langston & Forno (1978). Both Lewy and Langston & Forno found a predilection of Lewy body formation in specific hypothalamic nuclei with the tuberomammillary, lateral, and posterior areas containing by far the highest average counts per nucleus. Selective vulnerability of the tuberomammillary, lateral, and posterior hypothalamic cell groups to degeneration has been observed also in aging, postencephalitic Parkinsonism, Alzheimer's disease, and schizophrenia. The susceptibility of these particular nuclei to degenerative changes including Lewy body formation is not presently understood nor are the mechanisms by which Lewy bodies are formed in PD and other CNS disorders. Accumulation of amines, a pathological process which follows degeneration of catecholamine-containing neurons in experimental animals, also occurs most frequently in the lateral and posterior hypothalamic areas. In the present communication we propose that in PD, amine accumulation may be a precursor to Lewy body formation and that the susceptibility of certain hypothalamic areas to Lewy body formation may be related to their propensity to accumulate amines. Furthermore, the frequent co-existence of Lewy bodies and Alzheimer's neurofibrillary tangles in the lateral and posterior hypothalamic nuclei suggest that they may share a common pathogenetic etiology. If confirmed, this hypothesis may provide an experimental model by which the formation of Lewy bodies and neurofibrillary tangles may be investigated.

Sensitivity of dopamine receptors in the lateral hypothalamus is altered in 6-hydroxydopamine treated rats

Amine accumulation is observed in the lateral hypothalamus (LH) after nigrostriatal neurons degenerate. It has been proposed that this accumulation is a source of amines which are released into the hypothalamus thereby affecting the function of adjacent aminergic receptors. To approximate this condition of continuous exposure of LH receptors to endogenous amines, dopamine (DA) was injected into the LH of rats once daily for 5 consecutive days. A control group received 4 daily injections of tartaric acid vehicle and then DA on day 5. Rats pretreated with DA showed severe impairment of open field performance and motor reflex control on day 5 when they were compared to control animals which received vehicle pretreatment. In a second study, the DA receptor antagonist haloperidol was injected into the area of amine accumulation in the LH to determine whether this might block amine release from areas of accumulation thereby to attenuate lesion-induced rotation. Haloperidol administered once daily for 4 out of 7 days, once daily for 7 days or via a continuous infusion for 7 days, all reduced d,l-amphetamine-induced turning to control levels. These results suggest that prolonged exposure of hypothalamic DA receptors alters their sensitivity to subsequent doses of DA and that amine released from areas of accumulation may be blocked by haloperidol to enhance behavioral recovery from DA depleting lesions. Moreover, these findings indicate that the hypothalamus participates in the behavioral effects induced by DA depleting lesions and highlight the importance of hypothalamic pathology in Parkinson's disease.

Amelioration of experimental parkinsonism by intrahypothalamic administration of haloperidol

Accumulation of amines in the degenerating axons of ascending catecholamine-containing neurons in the hypothalamus has been proposed as a site of function neurotransmitter release and may thereby participate in the development of motor impairment seen after central dopamine-depleting lesions. To test this hypothesis further the dopamine receptor antagonist haloperidol (1 microL of a 14 nmol solution) was injected directly into the lateral hypothalamus (LH) in 6 different injection regimes to determine whether amphetamine-induced turning could be attenuated with this treatment. The injection of haloperidol at 1 and 24 h (group 1), 24 h (group 2) or 6+ 7 d (group 3) after 6-hydroxydopamine (6-OHDA) did not modify amphetamine-induced turning. However, the injection of haloperidol at 1 h, 24 h, 7 d, and 8 d (group 4), days 1-7 (group 5), or gradual infusion (14 nmol/microliters/h) for 7 days (group 6) all reduced the 6-OHDA-induced turning to a level similar to that of controls. These results add further support to the contention that amines are released from the axons of degenerating neurones in the hypothalamus and that this phenomenon participates in the elicitation of behavioral impairment attributed solely to the loss of functional neurotransmitters from terminal fields. Furthermore, the data emphasize the importance of hypothalamic pathology in the development of Parkinsonism and suggest that intrahypothalamic administration of dopamine blocking agents might be useful in the treatment of Parkinsonism.

Dysautonomia in Parkinson's disease: relationship to motor disability

Disturbances of autonomic nervous system functions are common in patients with Parkinson's disease (PD) and may develop as a result of pathology in centers of autonomic regulation such as the hypothalamus, brainstem, and sympathetic ganglia. We examined the relationship between the degree of motor disability, as determined from the Hoehn and Yahr scale (1967), and the presence of pandysautonomia, as determined by the assessment of noninvasive cardiovascular reflexes, in 29 unmedicated PD patients (mean age: 72.0 years, SD = 8.9). In addition, we investigated the relationship of pandysautonomia to CT scan measures of cerebral atrophy and to the presence or absence of pineal calcification. Nine patients (31.0%) were found to have pandysautonomia with deficits in both sympathetic and parasympathetic cardiovascular functions. Pandysautonomia was statistically related only to the degree of motor disability (p < .01). These findings demonstrate a significant association between motor disability and objective impairment of central cardiovascular functions in PD.

The relationship of tardive dyskinesia to positive schizophrenia

Investigations aimed at identifying the clinical characteristics that discriminate Tardive dyskinesia (TD) from non-TD patients have yielded disparate findings. A number of studies have suggested that TD may be a feature of negative schizophrenia. In particular, the association of TD with high prevalence of "soft" neurological signs, cognitive deficits, and abnormal brain morphology on CT scan in some patients, have led several investigators to propose that negative schizophrenia may be a risk factor for TD. The neurochemical profile of TD, however, is not consistent with this hypothesis. In the following communication, we present our studies which suggest that TD is specific to and an intergral part of positive schizophrenia. The data suggest that schizophrenic patients with predominant positive symptoms may be at increased risk for the development of TD. In addition, we present evidence linking TD with left cerebral hemispheric dysfunction. By comparison, we provide evidence that negative schizophrenia is related to diencephalic damage, and discuss its relevance to negative schizophrenia and to Parkinsonism. We also provide evidence that negative schizophrenia may be a risk factor for acute drug-induced dystonia. Thus, these findings are consistent with our model that negative schizophrenia is a risk factor for Parkinsonism, whereas positive schizophrenia is related to TD. In analogy with the positive/negative dichotomy of schizophrenia, we propose that TD could be considered a "positive," where Parkinsonism a "negative" movement disorder.

Resistance of beta-endorphin to dexamethasone inhibition in Parkinson's and Alzheimer's diseases

The response of plasma beta-endorphin (beta-EP) to dexamethasone suppression was studied in 14 patients with Alzheimer's disease (AD), 14 patients with Parkinson's disease (PD), and 13 age-matched controls in order to evaluate whether an impairment of the opiate system is present in these neurodegenerative disorders. Basal circulating beta-EP was in normal range in all subjects, although the mean concentration was slightly reduced in the patients compared to controls. After 1 mg dexamethasone given at 11:00 p.m. the night before, plasma beta-EP concentration measured at 08:00 a.m. and 04:00 p.m. was not inhibited in AD and PD patients while it was significantly reduced in controls. Circulating ACTH and cortisol were similar in patients and controls and a normal inhibition of plasma cortisol after dexamethasone was observed in 13/14 AD and 12/14 PD patients. The resistance of beta-EP to dexamethasone inhibition is consistent with previous clinical and experimental data indicating a disorder of the opiate system in brain degenerative diseases.

The relationship of negative schizophrenia to parkinsonism

The positive-negative distinction of schizophrenia has emerged as a valid means of clarifying its heterogeneity. Despite evidence that the two symptom classes may reflect different dimensions of the disease, there is presently no integrated model for understanding of the pathophysiology of these symptoms and their co-occurrence in schizophrenia. We propose that negative phenomena of schizophrenia may be a variant of Parkinsonism. This view is supported by the overlap with Parkinsonism in terms of clinical features, neurochemistry, pharmacology, as well as neuroradiological and neuropathological aspects. As such, negative symptoms may be a manifestation of disease of the basal ganglia and constitute the core pathology in schizophrenia. Positive symptoms, conversely, may reflect an "accessory" process related to a compensatory increase in striatal and limbic dopamine activity following an injury to the dopaminergic system. In the present communication we present a series of studies that support the association of negative schizophrenia and Parkinsonism. Based on this evidence, we suggest that schizophrenic patients with prominent negative symptoms might be managed like patients with Parkinson's disease, namely, with dopaminergic drugs and MAO-B inhibitors. Finally, the association of negative schizophrenia with Parkinsonism raises the possibility that adrenal medullary tissue transplantation, which may benefit a selected group of Parkinsonian patients, may be a future promising therapy for refractory negative schizophrenia.

The hypothalamus in MPTP-induced parkinsonism

1-methyl-4-phenyl-1,2,5,6-tetrahydropyridine (MPTP) has been shown to produce a parkinsonian syndrome in humans and other primates. Recent studies have demonstrated that in humans the hypothalamus has the highest binding density for (3H) MPTP, which corresponds to monoamine oxidase type B (MAO-B). There is evidence that the conversion of MPTP to the toxic compound MPP+ takes place in the hypothalamus; subsequently, MPP+ is transported to the striatal system, where destruction of nigrostriatal dopamine neurons occurs. Thus, the hypothalamus appears to be a primary target organ of MPTP toxicity. This assumption is supported by the observation that monkeys exposed to MPTP exhibit extensive pathological lesions in the hypothalamus which are manifested clinically by the development of life-threatening anorexia requiring forced feeding to overcome. We discuss the clinical implications of MPTP-induced hypothalamic damage to the pathophysiology of MPTP-induced parkinsonism and to Parkinson disease. It is suggested that consideration of hypothalamic involvement in MPTP-induced parkinsonism may provide a broader understanding of the pathophysiology of parkinsonism and may, in addition, account for the preliminary observations that MAO-B inhibitors retard the progression of Parkinson disease and possibly prolong life expectancy.

Melanocyte-stimulating hormone and persistent tardive dyskinesia: a hypothesis

An increased incidence of abnormal perioral movements has recently been reported in drug-naive pinealectomized rats with further accentuation of these movements following administration of haloperidol. Analysis of the temporal course of the development of the perioral dyskinetic movements revealed that the onset of these movements occurred within 4 days postoperatively and peaked at 3 weeks to plateau over the following 4-6 weeks. Increased pituitary Melanocyte-stimulating hormone (MSH) content has been reported in pinealectomized rats. Elevation of MSH content in the pinealectomized rats occurred within 3 days of surgery and was followed by normalization within 4 weeks. These findings suggest that compensatory mechanisms involving hypothalamic-pituitary MSH release must have been activated to induce normalization of pituitary MSH levels. Moreover, reduction of pituitary MSH levels may have coincided with attenuation in the severity of the perioral dyskinetic movements. It is possible that the development of tardive dyskinesia (TD) may in part be associated with increased brain and plasma MSH levels and that impaired hypothalamic-pituitary regulatory mechanisms of MSH release may be associated with persistent TD. The pineal gland may be implicated in this process as diminished melatonin secretion may be associated with disinhibition of MSH release. Thus, the above hypothesis complements and extends the recently presented "melatonin hypothesis" and suggests that research of pineal-hypothalamic interactions may be crucial to the further understanding of TD.

Mechanisms of action of ECT in Parkinson's disease: possible role of pineal melatonin

Recent clinical studies have suggested that electroconvulsive therapy (ECT) may be efficacious in the therapy of Parkinson's disease (PD). However, the mechanisms of action of ECT in PD are largely unknown. PD may be associated with reduction in the secretory activity of pineal melatonin, and the therapeutic efficacy of ECT in PD may be associated with an effect on the secretory activity of pineal melatonin. Further studies involving analysis of plasma melatonin levels and circadian release prior to and following ECT are needed more precisely to determine the role of pineal melatonin in PD and in the therapeutic efficacy of ETC in PD.

Pineal melatonin functions: possible relevance to Parkinson's disease

Barbeau hypothesized that Parkinson's disease is associated with hypothalamic deficiency of the specialized neuroendocrine cell system (A.P.U.D.) and that the degeneration of brainstem monoaminergic neurons is secondary to progressive functional loss of this cell system in the disease. The pineal gland meets criteria of the A.P.U.D. cell system and it is possible that dysfunction of the pineal gland may be associated with the pathophysiology and clinical manifestations of Parkinson's disease. Since the role of pineal melatonin in humans remains enigamatic, it is currently unclear which of the symptoms of Parkinson's disease may be associated with deregulation of the secretory activity of pineal melatonin. This review summarizes evidence linking possible alterations of pineal melatonin functions with the clinical manifestations of Parkinson's disease.

Pineal melatonin and sensory symptoms in Parkinson disease

Sensory symptoms have been reported in 40-60% of patients with Parkinson's disease, and in at least 10% of patients these symptoms precede the onset of the motor disorder. The pathophysiology of these symptoms remains unknown. Diminished brain serotonin concentration has been reported to be associated with sensory symptoms. Serotonin metabolism is regulated by pineal melatonin. The secretory activity of the pineal gland may be diminished in Parkinson's disease. In experimental animals pineal melatonin has been shown to exert analgesic effects by interacting with opiate receptors. In addition, since opioid peptides mediate the analgesic effects of melatonin, decreased opioid peptide functions in Parkinson's disease may be associated with disruption of the "fine-tuning" pain modulatory functions of melatonin and possibly indirectly facilitate the emergence of sensory symptoms.

Decreased catecholamine content in parkinsonian adrenal medullae

Autopsy specimens of adrenal medullae from parkinsonian and nonparkinsonian patients were analyzed for free catecholamines by high-performance liquid chromatography with electrochemical detection. The total free catecholamine content (nanomoles free catecholamine per milligram protein) was significantly lower in the parkinsonian patients than in the control population when the values were corrected for age and time from death to organ harvest. It is not established whether this decreased catecholamine content in the adrenals of parkinsonian patients is a concomitant of the disease itself or whether it is secondary to drug therapies used to treat the symptoms of Parkinson's disease.