CSF neurotransmitter markers in Alzheimer's disease

CSF neurotransmitter markers may reflect neurochemical alterations in Alzheimer's disease (AD). The best studied neurochemical deficit in AD is that of acetylcholine. Both acetylcholinesterase and butyrylcholinesterase activity have been reported to be reduced in some but not all studies of AD CSF. Studies of monoamine metabolites have also been controversial but most authors have found reduced concentrations of CSF HVA, lesser reductions in HIAA and no change in MHPG. CSF GABA concentrations have been found to be reduced in AD. Studies of CSF neuropeptides in AD have shown reduced concentrations of somatostatin and vasopressin, normal concentrations of vasoactive intestinal polypeptide and either normal or decreased concentrations of beta-endorphin and corticotropin releasing factor. Although no individual CSF neurochemical markers are specific for AD it may be possible to develop a profile of several neurochemical markers which will have enhanced specificity.     

Lesson from the Lesch-Nyhan syndrome

The Lesch-Nyhan syndrome is an inheritable disease associated with a specific biochemical deficiency, and which manifests itself particularly in the form of motor disorders. In this article Dr. Watts describes the biochemical lesion, and, through the understanding of the biochemistry, has been able to make some intriguing suggestions as to the role of guanosyl nucleotides in neurotransmission in general, and in learning-processes in particular.     

Animal models of Lesch-Nyhan syndrome

In humans, deficiency of the enzyme hypoxanthine-guanine phosphoribosyltransferase (HPRT) is associated with a disorder known as Lesch-Nyhan syndrome which includes severe neurobehavioral abnormalities. Several animal models which have been developed to examine the neurobiologic substrates of this disorder have suggested a role for abnormal function in purine/dopamine neurotransmission, but the relationship between HPRT-deficiency and these abnormalities remains unknown. Recently, HPRT-deficient mice have been produced which appear to have similar, though more subtle changes in brain dopamine function. These mice will be useful in elucidating the relationship between HPRT-deficiency and the neurological deficits observed in patients with this disorder.     

Behavior in the Lesch-Nyhan syndrome

The Lesch-Nyhan syndrome is a heritable disorder of the metabolism of uric acid in which behavioral manifestations are prominent and among the most provocative. The mutated or variant gene that determines this disorder is carried on the X chromosome. The disease is expressed exclusively in males. The molecular expression of the abnormal gene is in the completely defective activity of the enzyme hypoxanthine guanine phosphoribosyl transferase. As a result these patients overproduce uric acid and may develop early in life many of the clinical findings we associate with gout. They have in addition a variety of neurological abnormalities including mental retardation, spastic cerebral palsy, and involuntary, choreoathetoid movements. Involved patients have unusual, compulsive, aggressive behavior. Its most prominent but by no means exclusive feature is self-mutilation. The central feature in the management of this behavior is physical restraint. A number of practical procedures have been learned which facilitate the care and feeding of these patients. Promising new findings suggest that behavioral modification using extinction techniques and pharmacologic methods utilizing agents designed to increase the effective cerebral content of serotonin may each have a place in the management of behavior in this syndrome.Supported by research grants from the Public Health Service (DHEW), General Clinical Research Center #RR00827; from the National Institute of General Medical Sciences, National Institutes of Health, #GM 17702; and from the National Foundation-March of Dimes, #NF1377.     

Recurrent coma and Lesch-Nyhan syndrome.

A patient with Lesch-Nyhan syndrome has had 3 recurrent episodes of coma, each associated with an acute illness. Extensive investigation for known causes of coma has failed to yield a diagnosis. Although coma is not generally recognized as a feature of Lesch-Nyhan syndrome, similar patients have been reported previously. This and other episodic phenomena observed in Lesch-Nyhan syndrome may be explained by the disruption of cellular energy metabolism due to purine depletion, consequent to lack of the purine salvage pathway normally provided by the hypoxanthine-guanine-phosphoribosyl-transferase enzyme.     

Lesch-Nyhan syndrome: the differential diagnosis and actual aspects

The paper presents a case of a nine-year-old boy with Lesch-Nyhan syndrome whose disease was characterized by: a) clinical presentation (psychomotor retardation, involuntary movements, self-mutilatory behavior) b) biochemical features (increased levels of uric acid in serum and urine, index uric acid/creatinine) c) typical diagnostic ommision that lasted up to the terminal stage of the disease In order to provide the possibility of better diagnosis (which includes possibilities of genetic consulting, antenatal diagnosis and treatment of the disorder which is extremely unpleasant both to the patient and to his family) the most common diagnostic errors are discussed. Since the biochemical deficit is the only one which produces the occurrence of Lesch-Nyhan syndrome, the disease is commonly used as a model for investigations of the biochemical basis of human behavior.     

Seasonal variations of human lumbar CSF neurotransmitter metabolite concentrations

While circadian rhythms of many biological processes have been well characterized in humans, variations throughout the year have been little studied. Lumbar cerebrospinal fluid (CSF) neurotransmitter metabolite levels for homovanillic acid (HVA), 5-hydroxyindoleacetic acid (5-HIAA), and 3-methoxy-4-hydroxyphenyl glycol (MHPG) were determined in patients with schizophrenia and Alzheimer's disease. Samples from both groups taken during October through March had significantly higher levels of HVA and 5-HIAA, but not MHPG, than samples from April through September.     

A model of methotrexate encephalopathy: neurotransmitter and pathologic abnormalities

Methotrexate may cause seizures, dementia, and leukoencephalopathy when given in toxic doses to children with leukemia or solid tumors. Even in therapeutic doses, treatment with this drug is associated with an increased incidence of seizures in children with leukemia. To study mechanisms of injury, juvenile rats were given multiple intraventricular injections of methotrexate and the brains were analyzed for histopathology and biogenic amine metabolites of dopamine and serotonin. Disruption of monoamine metabolism has been proposed as a cause of brain dysfunction from this chemotherapy. Multiple injections (1 or 2 mg/kg) produced convulsions in an increasingly larger percentage of animals at higher cumulative doses, and five doses produced the neuropathological changes seen in human leukoencephalopathy. A single dose reduced the concentration of brain metabolites of dopamine, but not serotonin, six hours later. The effect was less pronounced after five doses. This rodent model should be useful for studying the metabolic basis of methotrexate encephalopathy.     

Gabapentin for self-injurious behavior in Lesch-Nyhan syndrome

Self-injurious behavior is a common clinical problem in children with Lesch-Nyhan syndrome, an X-linked disorder of purine metabolism. This behavior is not observed in other conditions associated with increased serum concentrations of uric acid, hypoxanthine, and xanthine. Various neurotransmitters appear to play a pivotal role in self-injurious behavior. The authors present a patient with Lesch-Nyhan syndrome, whose self-injurious behavior was effectively treated with gabapentin, and discuss possible mechanisms of action.     

Isoniazid-induced alteration of CSF neurotransmitter amino acids in Huntington's disease

During a randomized, double-blind, crossover, placebo-controlled clinical trial of isoniazid (plus pyridoxine) in Huntington's disease (HD), amino acids and related amino compounds were measured in both cerebrospinal fluid (CSF) and plasma utilizing a newly developed high-performance liquid chromatography ion-exchange/fluorometric assay method. Results showed that isoniazid (plus pyridoxine) significantly elevated the mean (+/- S.E.M.) levels of gamma-aminobutyric acid, aspartate, asparagine, homocarnosine, ornithine, histidine, alpha-aminobutyric acid, isoleucine, leucine and alanine in CSF and the levels of beta-alanine in both CSF and plasma. These alterations can be traced to inhibition of decarboxylation and transamination reactions requiring the cofactor pyridoxal phosphate and may be related to the observed equivocal clinical response in the HD patients. The differential influence of isoniazid on plasma and CSF amino acid profiles suggests that alterations of CNS amino acid metabolism may be reflected in CSF, and that isoniazid-induced alterations of amino acid metabolism in the CNS differ from those in the periphery.     

Hypothesized deficiency of guanine-based purines may contribute to abnormalities of neurodevelopment, neuromodulation, and neurotransmission in Lesch-Nyhan syndrome

The Lesch-Nyhan syndrome is a devastating sex-linked recessive disorder resulting from almost complete deficiency of the activity of hypoxanthine phosphoribosyltransferase (HPRT). The enzyme deficiency results in an inability to synthesize the nucleotides guanosine monophosphate and inosine monophosphate from the purine bases guanine and hypoxanthine, respectively, via the "salvage" pathway and an accelerated biosynthesis of these purines via the de novo pathway. The syndrome is characterized by neurologic manifestations, including the very dramatic symptom of compulsive self-mutilation. The neurologic manifestations may result, at least in part, from a mixture of neurodevelopmental (eg, a failure to "arborize" dopaminergic synaptic terminals) and neurotransmitter (eg, disruption of GABA and glutamate receptor-mediated neurotransmission) consequences. HPRT deficiency results in elevated extracellular levels of hypoxanthine, which can bind to the benzodiazepine agonist recognition site on the GABA(A) receptor complex, and the possibility of diminished levels of guanine-based purines in discrete "pools" involved in synaptic transmission. In addition to their critical roles in metabolism, gene replication and expression, and signal transduction, guanine-based purines may be important regulators of the synaptic availability of L-glutamate. Guanine-based purines may also have important trophic functions in the CNS. The investigation of the Lesch-Nyhan syndrome may serve to clarify these and other important neurotransmitter, neuromodulatory, and neurotrophic roles that guanine-based purines play in the central nervous system, especially the developing brain. A widespread and general deficiency of guanine-based purines would lead to impaired transduction of a variety of signals that depend on GTP-protein-coupled second messenger systems. This is less likely in view of a prominent localized pathologic effect of HPRT deficiency on presynaptic dopaminergic projections to the striatum. A possible more circumscribed effect of a deficiency of guanine-based purines could be interference with modulation of glutamatergic neurotransmission. Guanosine has been shown to be an important modulator of glutamatergic neurotransmission, promoting glial reuptake of L-glutamate. A deficiency of guanosine could lead to dysregulated glutamatergic neurotransmission, including possible excitotoxic damage. Unfortunately, although the biochemical lesion has been known for quite some time (ie, HPRT deficiency), therapeutically beneficial interventions for these affected children and adults have not yet emerged based on this elucidation. Conceivably, guanosine or its analogues and excitatory amino acid receptor antagonists could participate in the pharmacotherapy of this devastating disorder.     

Botulinum toxin: treatment of self-mutilation in patients with Lesch-Nyhan syndrome

Lesch-Nyhan syndrome (LNS) is a rare X-linked recessive disorder involving purine metabolism caused by the congenital absence of hypoxanthine guanine phosphoribosyl transferase. A characteristic feature of LNS is the appearance of intractable self-injurious behavior, usually in the form of severe lip and finger biting. The mechanism behind this severe self-mutilating behavior is unknown, and is one of the main challenges in the management of this condition. We here report the case of a 30-year-old man with a confirmed diagnosis of LNS who was successfully treated for self-mutilation of his lips with repeated botulinum toxin A (BTX-A) injections in the facial perioral muscles. Our findings suggest that treatment with BTX-A helped reduce self-abusive behavior in this patient. Our case illustrates that BTX-A injections can be a useful therapeutic approach in patients with self-abusive behavior.     

Self-injurious behaviour in young children with Lesch-Nyhan syndrome

The early development of self-injurious behaviour in three young boys (aged 17, 25, and 30 months at start of study) with Lesch-Nyhan syndrome was examined by means of parental interviews and by direct observations completed at 3 to 4 monthly intervals over an 18-month period. Results suggest that the self-injury began in a different way from that of other young children with autism and/or developmental disabilities in that, from the start, self-injurious responses were sudden and violent, rather than emerging gradually over time. Drastic measures, such as removal of the teeth or provision of tooth guards, were often taken to prevent further tissue damage. Direct observations showed that the boys' self-injury occurred at lower rates, but their carers were highly concerned about the behaviour. Sequential analysis of the observational data indicated that on some occasions the children were more likely to self-injure during periods of low social interaction, suggesting that their self-injury may have been influenced by environmental factors. The theoretical and practical implications of these findings are discussed.     

Dopamine receptor upregulation in Lesch-Nyhan syndrome: a postmortem study.

The brains of two patients with Lesch-Nyhan syndrome (LNS) were studied. The concentration of dopamine was decreased in the caudate nucleus of LNS patients. Immunohistochemical methods revealed that the dopamine (DA) D1 and D2 receptor and methionine-enkephalin immunoreactivities (IRs) were increased in the putamen, and less significantly in the caudate nucleus. The D1 and D2 receptor IRs of the cingulate cortex, the tryptophan-hydroxylase IR in the dorsal nucleus of the midbrain, as well as the substance P and methionine-enkephalin IRs of the nociception-conducting structures, including the periaqueductal gray and spinal trigeminal nucleus, were not changed. Tyrosine-hydroxylase IR was not decreased in the substantia nigra of the LNS patients. Therefore, the cause of the decreased dopaminergic activity in LNS may not be involved in the production of tyrosine hydroxylase in the substantia nigra. Developmental abnormalities due to the DA defect at an early age might exist in the postsynaptic structure in the striatum.     

Schizophrenia: a subcortical neurotransmitter imbalance syndrome?

Recent animal experiments suggest that glutamate plays a fundamental role in the control of psychomotor activity. This is illustrated by the finding that even in the virtually complete absence of dopamine, a marked behavioral activation is produced in mice following suppression of glutamatergic neurotransmission. This article discusses the possibility that a deficient activity within the cortico-striatal glutamatergic pathway is an important pathophysiological component in some cases of schizophrenia and that glutamatergic agonists may prove beneficial in this disorder. In a broader perspective, schizophrenia may be looked upon as a syndrome induced by a neurotransmitter imbalance in a feedback-regulated system, where dopamine and glutamate play a crucial role in controlling arousal and the processing of signals from the outer world to the cerebral cortex via the thalamus.     

Relationship between CSF neurotransmitter metabolites and aggressive behavior in Alzheimer's disease

To assess neurochemical correlates of aggressive behavior in Alzheimer's disease (AD) we examined concentrations of homovanillic acid (HVA) and 5-hydroxyindolacetic acid (5-HIAA) in lumbar cerebrospinal fluid (CSF) of 11 clinically diagnosed Alzheimer's disease (AD) patients and 12 non-demented age-equivalent controls. There were no significant differences between AD patients and controls in CSF HVA concentrations. However, the CSF 5-HIAA content was significantly lower in AD patients compared to controls. Patients without aggressive behavior had significantly lower concentrations of HVA and 5-HIAA than those with aggression, in whom concentrations were preserved compared to non-demented controls.