Neurotransmitter markers in the cerebrospinal fluid of normal subjects. Effects of aging and other confounding factors

Seasonality of brain function: role in psychiatric disorders

Seasonality patterns are reported in various psychiatric disorders. The current paper summarizes findings on brain adaptations associated with seasonal changes, factors that contribute to individual differences and their implications for psychiatric disorders. Changes in circadian rhythms are likely to prominently mediate these seasonal effects since light strongly entrains the internal clock modifying brain function. Inability of circadian rhythms to accommodate to seasonal changes might increase the risk for mood and behavior problems as well as worse clinical outcomes in psychiatric disorders. Understanding the mechanisms that account for inter-individual variations in seasonality is relevant to the development of individualized prevention and treatment for psychiatric disorders. Despite promising findings, seasonal effects are still understudied and only controlled as a covariate in most brain research. Rigorous neuroimaging studies with thoughtful experimental designs, powered sample sizes and high temporal resolution alongside deep characterization of the environment are needed to better understand the seasonal adaptions of the human brain as a function of age, sex, and geographic latitude and to investigate the mechanisms underlying the alterations in seasonal adaptation in psychiatric disorders.

Concentration gradients of monoamines, their precursors and metabolites in serial lumbar cerebrospinal fluid of neurologically healthy patients determined with a novel LC-MS/MS technique

BACKGROUND

Potential biomarkers for neuropsychiatric disorders are cerebrospinal fluid (CSF) monoamines and their corresponding precursors and metabolites. During CSF sampling, CSF flows towards the lumbar sampling site from more cranial regions. To compare the results of studies in which different CSF volumes were acquired, it is important to know if ventricular-lumbar concentration gradients exist. This has only been addressed for a few biogenic amines, and almost exclusively in neurologically unwell patients due to the burden of a lumbar puncture (necessary to obtain CSF). The aim of our study was to determine if concentration gradients exist for routinely measured CSF constituents and biogenic amines in neurologically healthy patients. We applied a novel ultrasensitive liquid chromatography mass spectrometry (LC-MS/MS) method for the simultaneous quantification of multiple monoamines, precursors and metabolites in CSF and plasma.

METHODS

CSF and blood samples were collected from twenty neurologically healthy patients undergoing spinal anaesthesia. Ten mL of lumbar CSF was collected in five consecutive two mL fractions. We determined leucocyte and erythrocyte counts, glucose, albumin and protein concentrations and quantified monoamines, precursors and metabolites on each of the fractions using LC-MS/MS.

RESULTS

In twenty patients (60% male; median age: 46 years), dopamine, DOPAC, 3-MT, HVA, noradrenaline, normetanephrine and 5-HIAA concentrations increased from the first to the last CSF fraction (all p < 0.001). CSF adrenaline concentrations were below the detection limit, whereas serotonin measurements were regarded as unreliable. Albumin and total protein levels decreased significantly across CSF fractions.

CONCLUSIONS

A ventricular-lumbar CSF concentration gradient existed for most of the investigated analytes. This is a novel finding for dopamine, noradrenaline, 3-MT and normetanephrine. These results contribute to the understanding of the neurobiology and underline the importance of standardized procedures for CSF handling to allow comparisons between studies.

Daytime and season do not affect reinforcement learning capacity in a response time adjustment task

Seasonal and circadian rhythms have a broad impact on physiological aspects, such as dopamine neurotransmission, and may be involved in the etiology of mood disorders. Considering this, studies on the influence of season and daytime on cognitive function are rare. The present study aimed to assess the impact of seasonal and diurnal effects on the ability to maximize reward outcomes by optimizing response times adaptively. For this purpose, a reward-based learning task that required an adaptation of response time to either a fast or a slow response was used. Eighty German participants (mean age ± SD = 21.86 ± 1.89 years, 41 women) were examined twice, in the morning and in the evening. Half of the participants were tested during the summer, while the other half performed the test in the winter. No impact of daytime, season or of the external factors photoperiodicity and temperature on reinforcement learning could be found. However, a generally slower response speed in the morning compared to the evening appeared. Previously conducted tasks could not display behavioral differences in both times of season and daytime, although neurophysiological findings suggest it.

Longitudinal Analysis of Multiple Neurotransmitter Metabolites in Cerebrospinal Fluid in Early Parkinson's Disease

BACKGROUND

Cerebrospinal fluid (CSF) levels of monoamine metabolites may represent biomarkers of Parkinson's disease (PD).

OBJECTIVE

The aim of this study was quantification of multiple metabolites in CSF from PD versus healthy control subjects (HCs), including longitudinal analysis.

METHODS

Absolute levels of multiple monoamine metabolites in CSF were quantified by liquid chromatography coupled with tandem mass spectrometry from 161 individuals with early PD and 115 HCs from the Parkinson's Progression Marker Initiative and de novo PD (DeNoPA) studies.

RESULTS

Baseline levels of homovanillic acid (HVA) and 3,4-dihydroxyphenylacetic acid (DOPAC) were lower in individuals with PD compared with HCs. HVA levels correlated with Movement Disorder Society Unified Parkinson's Disease Rating Scale total scores (P < 0.01). Both HVA/dopamine and DOPAC/dopamine levels correlated with caudate nucleus and raw DOPAC with putamen dopamine transporter single-photon emission computed tomography uptake ratios (P < 0.01). No metabolite changed over 2 years in drug-naive individuals, but some changed on starting levodopa treatment.

CONCLUSIONS

HVA and DOPAC CSF levels mirrored nigrostriatal pathway damage, confirming the central role of dopaminergic degeneration in early PD. © 2021 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

The Anaesthetic Biobank of Cerebrospinal fluid: a unique repository for neuroscientific biomarker research

Background

The pathophysiology of numerous central nervous system disorders remains poorly understood. Biomarker research using cerebrospinal fluid (CSF) is a promising way to illuminate the neurobiology of neuropsychiatric disorders. CSF biomarker studies performed so far generally included patients with neurodegenerative diseases without an adequate control group. The Anaesthetic Biobank of Cerebrospinal fluid (ABC) was established to address this. The aims are to (I) provide healthy-control reference values for CSF-based biomarkers, and (II) to investigate associations between CSF-based candidate biomarkers and neuropsychiatric symptoms.

Methods

In this cross-sectional study, we collect and store CSF and blood from adult patients undergoing spinal anaesthesia for elective surgery. Blood (20.5 mL) is collected during intravenous cannulation and CSF (10 mL) is aspirated prior to intrathecal local anaesthetic injection. A portion of the blood and CSF is sent for routine laboratory analyses, the remaining material is stored at -80 °C. Relevant clinical, surgical and anaesthetic data are registered. A neurological examination and Montreal Cognitive Assessment (MoCA) are performed pre-operatively and a subset of patients fill in questionnaires on somatic and mental health (depression, anxiety and stress).

Results

Four-hundred-fifty patients (58% male; median age: 56 years) have been enrolled in the ABC. The planned spinal anaesthetic procedure was not attempted for various reasons in eleven patients, in fourteen patients the spinal puncture failed and in twelve patients CSF aspiration was unsuccessful. A mean of 9.3 mL CSF was obtained in the remaining 413 of patients. Most patients had a minor medical history and 60% scored in the normal range on the MoCA (median score: 26).

Conclusions

The ABC is an ongoing biobanking project that can contribute to CSF-based biomarker research. The large sample size with constant sampling methods and extensive patient phenotyping provide excellent conditions for future neuroscientific research.

Functional abnormalities of striatum are related to the season-specific effect on schizophrenia

Schizophrenia is a syndrome that is typically accompanied by delusions, hallucinations and cognitive impairments. Specifically, abundant evidences support the notion that more people diagnosed with schizophrenia are born during fall-winter than spring-summer. Although pathophysiological of schizophrenia might be associated with abnormal brain functional network, little is currently known the relationship between season and deficient brain functional network of schizophrenia. To investigate this issue, in this study 51 schizophrenic subjects and 72 healthy controls underwent MRI scanning to detect the brain functional mapping, each at spring-summer and fall-winter season throughout the year. The data-driven method was used to measure the blood oxygen metabolism variability (BOMV). Decreased BOMV in spring-summer while increased in fall-winter were observed within dopaminergic network of schizophrenic subjects, including striatum, thalamus, and hippocampus. The post hoc analysis exploring the coupling among changed BOMV regions, confirmed that a positive relationship, between pallidum and hippocampus existed in fall-winter healthy controls, but not in fall-winter schizophrenic subjects. These findings identified that seasonal effect on striatum might be associated with modulation of striatum-hippocampus. Our results provide a new insight into the role of season in understanding the pathophysiological of schizophrenia.

Circadian insights into the biology of depression: Symptoms, treatments and animal models

In depression, symptoms range from loss of motivation and energy to suicidal thoughts. Moreover, in depression alterations might be also observed in the sleep-wake cycle and in the daily rhythms of hormonal (e.g., cortisol, melatonin) secretion. Both, the sleep-wake cycle and hormonal rhythms, are regulated by the internal biological clock within the hypothalamic suprachiasmatic nucleus (SCN). Therefore, a dysregulation of the internal mechanism of the SCN might lead in the disturbance of temporal physiology and depression. Hence, circadian symptoms in mood disorders can be used as important biomarkers for the prevention and treatment of depression. Disruptions of daily rhythms in physiology and behavior are also observed in animal models of depression, giving thus an important tool of research for the understanding of the circadian mechanisms implicated in mood disorders. This review discusses the alterations of daily rhythms in depression, and how circadian perturbations might lead in mood changes and depressive-like behavior in humans and rodents respectively. The use of animal models with circadian disturbances and depressive-like behaviors will help to understand the central timing mechanisms underlying depression, and how treating the biological clock(s) it may be possible to improve mood.

Low Daytime Light Intensity Disrupts Male Copulatory Behavior, and Upregulates Medial Preoptic Area Steroid Hormone and Dopamine Receptor Expression, in a Diurnal Rodent Model of Seasonal Affective Disorder

Seasonal affective disorder (SAD) involves a number of psychological and behavioral impairments that emerge during the low daytime light intensity associated with winter, but which remit during the high daytime light intensity associated with summer. One symptom frequently reported by SAD patients is reduced sexual interest and activity, but the endocrine and neural bases of this particular impairment during low daylight intensity is unknown. Using a diurnal laboratory rodent, the Nile grass rat (Arvicanthis niloticus), we determined how chronic housing under a 12:12 h day/night cycle involving dim low-intensity daylight (50 lux) or bright high-intensity daylight (1,000 lux) affects males’ copulatory behavior, reproductive organ weight, and circulating testosterone. We also examined the expression of mRNAs for the aromatase enzyme, estrogen receptor 1 (ESR1), and androgen receptor (AR) in the medial preoptic area (mPOA; brain site involved in the sensory and hormonal control of copulation), and mRNAs for the dopamine (DA) D1 and D2 receptors in both the mPOA and nucleus accumbens (NAC; brain site involved in stimulus salience and motivation to respond to reward). Compared to male grass rats housed in high-intensity daylight, males in low-intensity daylight displayed fewer mounts and intromissions when interacting with females, but the groups did not differ in their testes or seminal vesicle weights, or in their circulating levels of testosterone. Males in low-intensity daylight unexpectedly had higher ESR1, AR and D1 receptor mRNA in the mPOA, but did not differ from high-intensity daylight males in D1 or D2 mRNA expression in the NAC. Reminiscent of humans with SAD, dim winter-like daylight intensity impairs aspects of sexual behavior in a male diurnal rodent. This effect is not due to reduced circulating testosterone and is associated with upregulation of mPOA steroid and DA receptors that may help maintain some sexual motivation and behavior under winter-like lighting conditions.

Seasonal variation of spontaneous blink rate and beta EEG activity

Seasonal variations of the photoperiod have been shown to regulate biological and behavioral functions, with also effects on clinical symptom and course of several psychiatric conditions. Although melatonin is considered the principal signal used to transmit informations about the light and dark cycle, a dopamine (DA) role in regulating seasonal changes has been suggested. Few studies have addressed a seasonal pattern of dopamine, and human studies have been conducted on inter-subject differences, comparing measures obtained during fall-winter with those of spring-summer. We studied within-subject seasonal changes of blink rate (BR), a indirect marker of central DA activity, in 26 normal subjects (15 females and 11 males, mean age: 24.7 ± 4.0) during winter, spring, summer and fall. Occipital EEG activity and subjective measures of vigilance and mood were also assessed to account for variations on arousal and fatigue. A significant seasonal effect was found for BR, with higher rate in summer, and for EEG beta activity, with higher activity in spring and summer. Subjective fatigue was found higher in winter. According to our data, it is possible that higher BR and increased EEG beta activity result by an arousal activation sustained by dopamine systems during the months with a long photoperiod.

Light rescues circadian behavior and brain dopamine abnormalities in diurnal rodents exposed to a winter-like photoperiod

Seasonal affective disorder (SAD), beyond mood changes, is characterized by alterations in daily rhythms of behavior and physiology. The pathophysiological conditions of SAD involve changes in day length and its first-line treatment is bright light therapy. Animal models using nocturnal rodents have been studied to elucidate the neurobiological mechanisms of depression, but might be ill suited to study the therapeutic effects of light in SAD since they exhibit light-aversive responses. Here Arvicanthis ansorgei, a diurnal rodent, was used to determine behavioral, molecular and brain dopamine changes in response to exposure to a winter-like photoperiod consisting of a light-dark cycle with 8 h of light, under diminished light intensity, and 16 h of darkness. Furthermore, we evaluated whether timed-daily bright light exposure has an effect on behavior and brain physiology of winter-like exposed animals. Arvicanthis under a winter-like condition showed alterations in the synchronization of the locomotor activity rhythm to the light-dark cycle. Moreover, alterations in day-night activity of dopaminergic neurotransmission were revealed in the nucleus accumbens and the dorsal striatum, and in the day-night clock gene expression in the suprachiasmatic nucleus. Interestingly, whereas dopamine disturbances were reversed in animals exposed to daily light at early or late day, altered phase of the daily rhythm of locomotion was reverted only in animals exposed to light at the late day. Moreover, Per2 gene expression in the SCN was also affected by light exposure at late day in winter-like exposed animals. These findings suggest that light induces effects on behavior by mechanisms that rely on both circadian and rhythm-independent pathways influencing the dopaminergic circuitry. This last point might be crucial for understanding the mechanisms of non-pharmacological treatment in SAD.

Differences in Number of Midbrain Dopamine Neurons Associated with Summer and Winter Photoperiods in Humans

Recent evidence indicates the number of dopaminergic neurons in the adult rodent hypothalamus and midbrain is regulated by environmental cues, including photoperiod, and that this occurs via up- or down-regulation of expression of genes and proteins that are important for dopamine (DA) synthesis in extant neurons (‘DA neurotransmitter switching’). If the same occurs in humans, it may have implications for neurological symptoms associated with DA imbalances. Here we tested whether there are differences in the number of tyrosine hydroxylase (TH, the rate-limiting enzyme in DA synthesis) and DA transporter (DAT) immunoreactive neurons in the midbrain of people who died in summer (long-day photoperiod, n = 5) versus winter (short-day photoperiod, n = 5). TH and DAT immunoreactivity in neurons and their processes was qualitatively higher in summer compared with winter. The density of TH immunopositive (TH+) neurons was significantly (~6-fold) higher whereas the density of TH immunonegative (TH-) neurons was significantly (~2.5-fold) lower in summer compared with winter. The density of total neurons (TH+ and TH- combined) was not different. The density of DAT+ neurons was ~2-fold higher whereas the density of DAT- neurons was ~2-fold lower in summer compared with winter, although these differences were not statistically significant. In contrast, midbrain nuclear volume, the density of supposed glia (small TH- cells), and the amount of TUNEL staining were the same in summer compared with winter. This study provides the first evidence of an association between environmental stimuli (photoperiod) and the number of midbrain DA neurons in humans, and suggests DA neurotransmitter switching underlies this association.

Impacts of age on plasma monoamine metabolite concentrations in a large cohort of healthy individuals

The measurement of plasma concentrations of monoamine metabolites is a useful method for inferring the dynamics of monoamine metabolites in the brain. To clarify effects of age and sex on plasma monoamine metabolites levels, we used high-performance liquid chromatography to measure plasma levels of homovanillic acid (HVA), free and total 3-methoxy-4-hydroxyphenylglycol (MHPG), and 5-hydroxyindoleacetic acid (5-HIAA) in healthy men and women of various ages (n=214). In all plasma monoamine metabolites, there were significant differences across the age groups, and multiple comparisons revealed that older subjects had higher levels than younger subjects. Moreover, significant positive correlations were found between age and plasma levels of HVA, free MHPG, total MHPG, and 5-HIAA. On the other hand, plasma concentrations of monoamine metabolites were not influenced by sex, except for total MHPG for which the plasma levels were significantly higher in men than in women. Age-related changes in monoamine oxidase and renal function might affect our results. This large cohort survey provides further evidence to be cautiously aware of age effects when regarding plasma monoamine metabolites levels as reflections of central activity.

Revisiting the serotonin-aggression relation in humans: a meta-analysis

The inverse relation between serotonin and human aggression is often portrayed as "reliable," "strong," and "well established" despite decades of conflicting reports and widely recognized methodological limitations. In this systematic review and meta-analysis, we evaluate the evidence for and against the serotonin deficiency hypothesis of human aggression across 4 methods of assessing serotonin: (a) cerebrospinal fluid levels of 5-hydroxyindoleacetic acid (CSF 5-HIAA), (b) acute tryptophan depletion, (c) pharmacological challenge, and (d) endocrine challenge. Results across 175 independent samples and over 6,500 total participants were heterogeneous, but, in aggregate, revealed a small, inverse correlation between serotonin functioning and aggression, anger, and hostility (r = -.12). Pharmacological challenge studies had the largest mean weighted effect size (r = -.21), and CSF 5-HIAA studies had the smallest (r = -.06). Potential methodological and demographic moderators largely failed to account for variability in study outcomes. Notable exceptions included year of publication (effect sizes tended to diminish with time) and self- versus other-reported aggression (other-reported aggression was positively correlated to serotonin functioning). We discuss 4 possible explanations for the pattern of findings: unreliable measures, ambient correlational noise, an unidentified higher order interaction, and a selective serotonergic effect. Finally, we provide 4 recommendations for bringing much needed clarity to this important area of research: acknowledge contradictory findings and avoid selective reporting practices; focus on improving the reliability and validity of serotonin and aggression measures; test for interactions involving personality and/or environmental moderators; and revise the serotonin deficiency hypothesis to account for serotonin's functional complexity.

Cerebrospinal fluid norepinephrine and cognition in subjects across the adult age span

Adequate central nervous system noradrenergic activity enhances cognition, but excessive noradrenergic activity may have adverse effects on cognition. Previous studies have also demonstrated that noradrenergic activity is higher in older than younger adults. We aimed to determine relationships between cerebrospinal fluid (CSF) norepinephrine (NE) concentration and cognitive performance by using data from a CSF bank that includes samples from 258 cognitively normal participants aged 21-100 years. After adjusting for age, gender, education, and ethnicity, higher CSF NE levels (units of 100 pg/mL) are associated with poorer performance on tests of attention, processing speed, and executive function (Trail Making A: regression coefficient 1.5, standard error [SE] 0.77, p = 0.046; Trail Making B: regression coefficient 5.0, SE 2.2, p = 0.024; Stroop Word-Color Interference task: regression coefficient 6.1, SE 2.0, p = 0.003). Findings are consistent with the earlier literature relating excess noradrenergic activity with cognitive impairment.

Rostrocaudal dynamics of CSF biomarkers

The rostrocaudal gradient (RCG) of markers present in cerebrospinal fluid (CSF) has not been studied adequately due to lack of appropriate control populations and ethical restrictions. The aim of this study is to understand the rostrocaudal gradient of CSF biomarkers. We contacted a study comparing CSF levels of seven biomarkers from cisternal (rostral) and lumbar (caudal) CSF obtained from patients with trigeminal neuralgia and tension-type headache. The RCGs of CSF/serum albumin ratio, 8-isoprostane. GFAP, total tau and beta amyloid protein were higher than one. The RCGs of lactate, VEGF and the heavy chain of neurofilament protein were lower than one. The study provides new values for several commonly examined markers of cisternal CSF. Knowledge of the RCG gradient of different CSF markers is important in interpreting studies reporting ventricular CSF values.

Seasonal effects on human striatal presynaptic dopamine synthesis

Past studies in rodents have demonstrated circannual variation in central dopaminergic activity as well as a host of compelling interactions between melatonin--a scotoperiod-responsive neurohormone closely tied to seasonal adaptation--and dopamine in the striatum and in midbrain neuronal populations with striatal projections. In humans, seasonal effects have been described for dopaminergic markers in CSF and postmortem brain, and there exists a range of affective, psychotic, and substance abuse disorders that have been associated with both seasonal symptomatic fluctuations and dopamine neurotransmission abnormalities. Together, these data indirectly suggest a potentially crucial link between circannual biorhythms and central dopamine systems. However, seasonal effects on dopamine function in the living, healthy human brain have never been tested. For this study, 86 healthy adults underwent (18)F-DOPA positron emission tomography scanning, each at a different time throughout the year. Striatal regions of interest (ROIs) were evaluated for differences in presynaptic dopamine synthesis, measured by the kinetic rate constant, K(i), between fall-winter and spring-summer scans. Analyses comparing ROI average K(i) values showed significantly greater putamen (18)F-DOPA K(i) in the fall-winter relative to the spring-summer group (p = 0.038). Analyses comparing voxelwise K(i) values confirmed this finding and evidenced intrastriatal localization of seasonal effects to the caudal putamen (p < 0.05, false-discovery rate corrected), a region that receives dopaminergic input predominantly from the substantia nigra. These data are the first to directly demonstrate a seasonal effect on striatal presynaptic dopamine synthesis and merit future research aimed at elucidating underlying mechanisms and implications for neuropsychiatric disease and new treatment approaches.

Comparative evaluation of 5-HIAA (5-hydroxy indoleacetic acid) and HVA (homovanillic acid) in infantile hydrocephalus

BACKGROUND

Infantile hydrocephalus is a common congenital problem. Functional and behavioral disturbances associated with hydrocephalus may be due to altered neurotransmitters in the brain. The role of neurotransmitters has been established in various psychiatric and neurological conditions. Therefore, we decided to study the role of 5-hydroxy indoleacetic acid (5-HIAA) and homovanillic acid (HVA) in cerebrospinal fluid (CSF) of hydrocephalic patients as diagnostic and prognostic marker.

MATERIALS AND METHODS

Ventricular CSF samples were taken from hydrocephalic patients peroperatively and at days 7 & 30. Control CSF samples were taken from nonhydrocephalic patients operated for other conditions. Samples were analyzed for 5-HIAA and HVA, and results were obtained accordingly.

RESULTS

Values of 5-HIAA and HVA showed a highly significant decrease after shunt insertion. No significant difference in values of 5-HIAA and HVA were observed in relation to age and duration of disease. The CSF ventriculo-lumbar gradient for both 5-HIAA and HVA done in six patients was statistically significant only in the noncommunicating group.

CONCLUSION

Both the neurotransmitter metabolites 5-HIAA and HVA are found to be significantly high in the hydrocephalus, but 5-HIAA is a more sensitive parameter. These markers levels decrease after shunt insertion. Thus, estimation of these metabolites could be valuable markers for its diagnosis and follow-up.

Difficulties in establishing reference intervals for special fluids: the example of 5-hydroxyindoleacetic acid and homovanillic acid in cerebrospinal fluids

Biochemical measurements in “special fluids” are complicated with the problem of reference intervals. Reference intervals are difficult to establish for these types of samples since they are usually only collected in patients with clinical suspicion of disease. Determination of neurotransmitter metabolites in cerebrospinal fluid illustrates this difficulty. This paper will review the factors and circumstances that have been identified or are suspected to modifythe concentration of 5-hydroxyindoleacetic acid (5-HIAA) and homovanillic acid (HVA) in cerebrospinal fluid. In addition to obvious parameters such as age-related variation that can affect the concentration of 5-HIAA and HVA in cerebrospinal fluid, a varietyof other factors can explain the wide range of “control” group sizes reported in the literature. Reference intervals must take into account the purpose of cerebrospinal fluid examinations, whether they be prospective studies to explore physio-pathologic relationships or for diagnostic purposes. In the latter case, certain neurological disorders cannot be excluded if a single measured value is within the reference interval.

Decreased homovanillic acid concentrations in cerebrospinal fluid in children without a known defect in dopamine metabolism

Homovanillic acid (HVA) is a metabolite of dopamine, reflecting central dopamine metabolism, primarily situated in the striatum. Low HVA concentrations in the cerebrospinal fluid (CSF) may indicate metabolic deficiencies in the pathways of the biosynthesis or catabolism of dopamine. In this retrospective study, we investigated the clinical presentation of patients whose HVA concentration in the CSF had been determined routinely after spinal taps for a variety of clinical reasons. A decrease of HVA concentration in the CSF, due to a defect in the biosynthesis or reuptake of dopamine, is expected to cause extrapyramidal features. However, we found a remarkable variability in the clinical symptoms. Similarly, a decreased HVA concentration in the CSF failed to coincide with specific abnormalities at neuroimaging. In view of the diversity of the clinical presentation and in the absence of specific enzyme deficiencies, a decrease of HVA may be due to dysfunction of dopamine neurons, not resulting in specific extrapyramidal symptoms. Thus, with the exception of diseases associated with a specific enzyme deficiency in the metabolic pathways involving dopamine, a decrease of HVA concentration in the CSF is mainly a secondary or epiphenomenon in a variety of clinical conditions.

Suicidality, impulsivity and aggression--is there a link to 5HIAA concentration in the cerebrospinal fluid?

In biological suicide research, low cerebrospinal fluid-5-hydroxyindolacetic acid (CSF-5HIAA) concentrations have been associated with suicidality, aggression and impulsivity. However, it frequently appears that the interpretation of existing study results is flawed. The analysis of various published findings suggests that contaminating factors like impulsivity or depressive symptoms in suicide attempters are often not taken into consideration at the time of suicide. The seemingly 'robust' association of low CSF-5HIAA concentration with 'suicidality' and 'aggression' is in fact rather weak. Reported associations of subgroups of suicidal behavior (e.g. violent suicide attempts) with low CSF-5HIAA concentrations are likely to represent somewhat premature translations of findings from studies that have flaws in methodology. Furthermore, the perception of 'suicidal behavior' as autoaggressive behavior or inwardly directed aggression in the view of the authors may not be useful in biological suicide research. The construct of aggressivity is insufficiently defined, resulting in difficulties to interpret empirical data. Some evidence exists, however, that reduced CSF-5HIAA concentrations might be related to certain depressive symptoms and changes in impulsivity. More carefully designed studies are required to overcome the existing methodological shortcomings.

Cerebrospinal fluid somatostatin levels in febrile seizures and epilepsy in children

We analysed the level of cerebrospinal fluid (CSF) somatostatin in children with febrile seizures and epilepsy. In the febrile seizure group (n = 23), the somatostatin level was 83.9 +/- 11.2 pg/ml, which was significantly higher than that of age-matched controls. CSF samples obtained within 3 h of the last seizure had higher somatostatin levels (106.1 +/- 12.4 pg/ml;n = 14) than did the CSF obtained after 3 h (49.4 +/- 15.6 pg/ml;n = 9). The mean somatostatin level in the epilepsy group was 35.3 +/- 4.3 pg/ml (n = 34), and was distributed as follows: 27.6 +/- 3.6 pg/ml in the idiopathic generalized epilepsy group (n = 16), 44.0 +/- 9.4 pg/ml in the symptomatic generalized epilepsy group (n = 13), and 37.2 +/- 10.1 pg/ml in the partial epilepsy group (n = 5). The levels in each group were significantly higher than those in age-matched controls. Somatostatin is a hypothalamic tetradecapeptide with excitatory effects on neurons in children with febrile seizures and epilepsy. The finding that patients with convulsive disease had elevated levels of CSF somatostatin suggests that somatostatin release is somehow related to seizure activity. It remains to be determined whether this is due to increased release from over-active excitatory neurons or leakage from damaged or anoxic neurons, secondary to seizure activity.

Effect of chronic treatment with piracetam and tacrine on some changes caused by thymectomy in the rat brain

Thymectomized rats, 5 weeks after surgery, showed a significant impairment in learning and memory as shown by deficits in passive avoidance and in the Morris water maze test. The behaviour of the thymectomized rats in the "open field" apparatus was largely unchanged. Following treatment for 20 days with either piracetam (500 mg/kg) or tacrine (3.0 mg/kg), the deficit in passive avoidance learning was largely reversed. Chronic treatment with tacrine also reversed the deficit in the behaviour of the thymectomized rats in the Morris water maze. The effects of thymectomy on the biogenic amines and some of their metabolites in the amygdaloid cortex, hypothalamus, striatum and olfactory bulbs were also determined. Relative to the sham-operated controls, thymectomy resulted in a reduction in the noradrenaline concentration in the amygdala, hypothalamus, and olfactory bulbs. This effect was reversed by chronic piracetam and tacrine treatments. The concentration of dopamine was also reduced in the olfactory bulbs after thymectomy whereas in the striatum the concentration of 5-hydroxytryptamine (5-HT; serotonin) was increased. The concentration of gamma amino butyric acid (GABA) was determined in amygdaloid cortex and hippocampus only. The only significant change occurred following chronic treatment of thymectomized rats with tacrine, when a significant elevation of GABA was found. Neither piracetam nor tacrine produced any change in the amines of their metabolites in the sham-operated controls. Tacrine, however, elevated the dopamine and reduced the 5-HT content of the hypothalamus and increased the 3,4-dihydroxylphenylacetic acid concentration of the striatum of thymectomized rats. Examination of the differential white blood cell count of the thymectomized rats showed that the percentage of lymphocytes was decreased, and the percentage of neutrophils increased, relative to the sham-operated controls. Chronic lacrine, but not piracetam, treatment reversed the lesion-induced changes.

Sex differences in plasma homovanillic acid levels in schizophrenia and normal controls: relation to neuroleptic resistance

Plasma homovanillic acid (pHVA) levels were compared in a large number of neuroleptic-resistant and -responsive schizophrenic patients (male/female = 161/46) and normal controls (67/27), and correlated with various measures of psychopathology. Psychopathology was evaluated with the brief psychiatric rating scale, the Schedule for Affective Disorders and Schizophrenia-Change version (SADS-C) and SADS-C Global Assessment Scale, the Scale for Assessment of Negative Symptoms, the Scale for Assessment of Positive Symptoms (SAPS), and the Quality of Life Scale. No significant differences in pHVA levels between neuroleptic-resistant (n = 104) or -responsive (n = 103) schizophrenic patients, and normal controls, were found; however, there was a main effect for sex, due to higher pHVA levels in women than men. There were no diagnosis x gender or age effects on pHVA levels. No significant correlations were observed between psychopathology ratings and baseline pHVA levels, except with the Hallucinations subscale of SAPS in neuroleptic-responsive patients. Neither duration of neuroleptic washout nor plasma prolactin levels correlated with pHVA levels. Further studies on the origin and significance of the gender difference in pHVA are indicated.

Dopamine-related genes and their relationships to monoamine metabolites in CSF

Monoamine metabolite (MM) levels in lumbar cerebrospinal fluid (CSF) are extensively used as indirect estimates of monoamine turnover in the brain. In this study we investigated genotypes for DNA polymorphisms in the D2 (DRD2), D3 (DRD3), and D4 (DRD4) dopamine receptor and tyrosine hydroxylase (TH) genes and their relationships to CSF MM in healthy volunteers (n = 66). Concentrations of homovanillic acid (HVA), 3-methoxy-4-hydroxyphenylglycol (MHPG), and 5-hydroxyindoleacetic acid (5-HIAA) were corrected for back length, a confounding variable. Corrected MM levels were not related to age, gender, height, weight heredity, season or atmospheric pressure at sampling. Individuals with specific DRD2 and TH allele and genotype configurations significantly differed in HVA and MHPG concentrations. DRD3 homo- and heterozygotic genotypes had significantly different CSF 5-HIAA levels. DRD4 genotypes were not related to MM concentrations. The results suggest that specific DRD2, DRD3, and TH genotypes participate in the regulation of monoamine turnover in the central nervous system. Accordingly monoamine receptors and synthesizing enzyme genotypes appear to be variance factors influencing MM concentrations in CSF. The relationships found in this study support MM concentrations as markers for monoamine transmission in the human brain.

The significance of the activity of CSF cholinesterases in dementias

This article reviews the significance of changes in the level of cerebrospinal fluid acetylcholinesterase or cholinesterase in patients with Alzheimer's disease or other dementias. Evidence has shown that the methodology of assaying cerebrospinal fluid acetylcholinesterase or cholinesterase is reliable and the activity of the enzyme is stable. Low acetylcholinesterase or cholinesterase levels presenting in cerebrospinal fluid of a demented individual may confirm the clinical diagnosis of Alzheimer's disease or other organic dementia. A low activity of acetylcholinesterase or cholinesterase existing in cerebrospinal fluid of a non-demented individual may indicate a brain at risk, or that the person is in the preclinical stage of dementia. Recognition of the presence of the preclinical stage may be very beneficial for explaining the real meaning of the 'overlap' in the biochemistry and pathology between dementia and non-dementia, and also very important for prevention and treatment. Therefore, the strategy of prevention and of treatment should no longer be designed to inhibit acetylcholinesterase activity. In contrast, it should be designed to enhance the neuronal acetylcholinesterase activity or to delay the degeneration of brain acetylcholinesterase system.

CSF somatostatin increase in patients with early parkinsonian syndrome

Somatostatin-like immunoreactivity levels (SLI) in cerebrospinal fluid (CSF) were determined in twenty-three patients with untreated parkinsonian syndrome (15 with Idiopathic Parkinson's disease (IPD) and 8 with other forms of parkinsonism) at the moment of clinical diagnosis (mean duration of disease 1.1 +/- 0.2 years), and in 26 subjects without neurological symptoms. None of the IPD patients had a diagnosis of dementia at the moment of inclusion in the study. CSF-SLI content was found to be significantly higher in patients with parkinsonian syndrome (107.9 +/- 9.8 pg/ml) than in control subjects (73.5 +/- 8.4 pg/ml). The increase was also significant when controls were compared with IPD patients. In addition, a positive correlation between SLI and homovanillic acid was found in CSF of all patients. A test of learning memory was used to evaluate the mental state of patients and a significant increase in CSF-somatostatin levels was observed in patients with Idiopathic Parkinson's disease and severe affectation of memory. These results indicate that in the early steps of untreated parkinsonian syndrome, somatostatin concentration in cerebrospinal fluid may increase, probably due to the neurodegenerative depletion of somatostatin from striatal or cortical neurons.

Cerebrospinal monoamine metabolites and amino acid content in patients with parkinsonian syndrome and rats lesioned with MPP+

Monoamine metabolites and amino acid concentration in cerebrospinal fluid (CSF) of 33 untreated patients with parkinsonian syndrome, and 20 control patients without specific neurological symptoms have been compared with those obtained in cerebrospinal fluid of rats intrastriatally lesioned with 1-methyl-4-phenylpyridinium ion (MPP+) and sham operated animals. Homovanillic acid content was found to be significantly lower in patients with severe parkinsonism (motor score of UPDRS > 24), but not in patients with mild symptoms (motor score < or = 24). A correlation between the loss of striatal dopamine and the decrease in cerebrospinal homovanillic acid has been established in rats treated with MPP+. The extrapolation of these results to those obtained from human patients could be important in assessing the degree of striatal dopamine loss shown by humans with parkinsonian syndrome at the moment of clinical diagnosis. No significant differences were found between the other monoamine metabolites analyzed and free amino acid content in human and rat CSF.

Effects of clozapine on CSF homovanillic acid in spasmodic torticollis

We studied the effect of the atypical neuroleptic clozapine (CLO) on homovanillic acid (HVA) in cerebrospinal fluid (CSF) in five patients with spasmocid torticollis. Lumbar puncture was performed before and on the seventh day of CLO treatment. Although an HVA elevation was to be expected because of the antidopaminergic action of CLO, statistical analysis failed to reveal any significant increase of HVA under CLO treatment. Thus significance of CSF HVA may be less important for the description of antidopaminergic action of neuroleptics than previously assumed.

Acetylcholinesterase provides deeper insights into Alzheimer's disease

This article reviews the considerable evidence which rejects the cholinergic hypothesis of Alzheimer's disease (AD) and proposes that it is the AChE system of which the lightly stained neurons are located in the entorhinal cortex, the CA1/subiculum of the hippocampus and the amygdala which are the most vulnerable and are the earliest affected in the pathological processes of AD. Changes then spread out to the intermediately stained neurons of the association cortex, until they affect the heavily stained cells of the motor cortex. In general, senile plaque, a hallmark of AD, may be formed from the terminals of AChE-containing neurons. Neurofibrillary tangle, another hallmark of AD, may be formed in the perikarya of AChE-containing cells and bring about the demise of the neuron, thus leading to dementia.

Cognitive and memory deficits in untreated Parkinson's disease and amyotrophic lateral sclerosis patients: a comparative study

We investigated the profile of cognitive and memory deficits of 22 Parkinson's disease (PD), 24 amyotrophic lateral sclerosis (ALS) patients and 26 age-matched controls. The patients were at the early phase of the disease and untreated. The ALS patients exhibited deficits in simple visuoperceptual functions and in complex visuoperceptual reasoning (Digit Symbol and Block Design tests), whereas the PD patients showed deficits only in simple visuoperceptual functions. Moreover, both ALS and PD patients had impairment in tasks requiring set shifting from one reaction to another that may suggest frontal lobe dysfunction. The ALS and PD patients also showed impairment in the task of learning a word list with effort-demanding organization of the material to be remembered. However, preserved delayed recall of logical passages suggests that memory, per se, is not impaired in ALS or in PD. The patterns of errors in a test of recognition of learned words imply, at least partially, different underlying deficits in the two diseases. An inability to inhibit irrelevant information may contribute to memory impairment in ALS patients, whereas the memory deficit in PD may derive from lowered motivation or initiating behaviour.

Cerebrospinal fluid monoamine metabolites in 114 healthy individuals 18-88 years of age

Concentrations of the monoamine metabolites homovanillic acid (HVA), 5-hydroxy-indoleacetic acid (5-HIAA) and 4-hydroxy-3-methoxyphenylglycol (HMPG) were determined in lumbar cerebrospinal fluid (CSF) of 114 healthy individuals, 18-88 years of age, without histories, symptoms or signs of central nervous system dysfunction. The mean values (+/- SD) were 253 +/- 109 nmol/l for HVA, 125 +/- 54 nmol/l for 5-HIAA, 47 +/- 10 nmol/l for HMPG, and 2.10 +/- 0.52 for the HVA/5-HIAA ratio. Analyses of confounding factors revealed that all metabolites correlated negatively with body height, the values being lower in taller than in shorter individuals. This is probably attributable to a larger surface area for monoamine metabolite transport from the subarachnoid space in taller than in shorter individuals. These correlations make statistical adjustment for body height important in analyses of monoamine metabolite levels. Without considering body height, all monoamine metabolites showed a positive correlation with age, and higher levels of HVA and 5-HIAA were found in women than men. After statistical adjustment for the influence of body height, no differences in CSF monoamine metabolites levels were found between the sexes, and only 5-HIAA showed a positive correlation with age. There were no significant seasonal variations for any of the monoamine metabolites.

Age-related cognitive decline and electroencephalogram slowing in Down's syndrome as a model of Alzheimer's disease

We studied quantitative electroencephalogram and neuropsychological performance in an aging series of 31 patients with Down's syndrome and compared the findings with those of 36 patients with probable Alzheimer's disease and age-matched controls. We found an age-related decline of cortical functions and slowing of the electroencephalogram in Down's syndrome patients aged from 20 to 60 years. Slowing of the electroencephalogram, i.e. the decrease of the peak frequency, was significantly related to Mini-Mental status scores, and visual, praxic and speech functions, as well as memory in the Down patients, similar to the Alzheimer patients. Similar correlations were not demonstrated for young or elderly controls. This study provides neuropsychological and electrophysiological data to suggest that studying Down's syndrome patients of different ages can serve as a model for progression of Alzheimer's disease.

Detection of glutamine synthetase in the cerebrospinal fluid of Alzheimer diseased patients: a potential diagnostic biochemical marker

In this report, 8- and 2-azidoadenosine 5'-[gamma-32P]triphosphate were used to examine cerebrospinal fluid (CSF) samples for the presence of an ATP binding protein unique to individuals with Alzheimer disease (AD). A 42-kDa ATP binding protein was found in the CSF of AD patients that is not observed in CSF from normal patients or other neurological controls. The photolabeling is saturated with 30 microM 2-azidoadenosine 5'-[gamma-32P]triphosphate. Photoinsertion can be totally prevented by the addition of 25 microM ATP. Photoinsertion of 2-azidoadenosine 5'-triphosphate into the protein is only weakly protected by other nucleotides such as ADP and GTP, indicating that this is a specific ATP binding protein. A total of 83 CSF samples were examined in a blind manner. The 42-kDa protein was detected in 38 of 39 AD CSF samples and in only 1 of 44 control samples. This protein was identified as glutamine synthetase [GS; glutamate-ammonia ligase; L-glutamate:ammonia ligase (ADP-forming), EC 6.3.1.2] based on similar nucleotide binding properties, comigration on two-dimensional gels, reaction with a polyclonal anti-GS antibody, and the presence of significant GS enzyme activity in AD CSF. In brain, GS plays a key role in elimination of free ammonia and also converts the neurotransmitter and excitotoxic amino acid glutamate to glutamine, which is not neurotoxic. The involvement of GS, if any, in the onset of AD is unknown. However, the presence of GS in the CSF of terminal AD patients suggests that this enzyme may be a useful diagnostic marker and that further study is warranted to determine any possible role for glutamate metabolism in the pathology of AD.

Brain and cerebrospinal fluid cholinesterases in Alzheimer's disease, Parkinson's disease and aging. A critical review of clinical and experimental studies

Acetylcholinesterase (AChE), an enzyme responsible for the break-down of acetylcholine, is found both in cholinergic and non-cholinergic neurons in the central nervous system. In addition to its role in the catabolism of acetylcholine, AChE have other functions in brain, e.g. in the processing of peptides and proteins, and in the modulation of dopaminergic neurons in the brain stem. Several clinical and experimental studies have investigated AChE in brain and cerebrospinal fluid (CSF) in aging and dementia. The results suggest that brain AChE and its molecular forms show interesting changes in dementia and aging. However, CSF-AChE activity is not a very reliable or sensitive marker of the integrity and function of cholinergic neurons in the basal forebrain complex. Additional work is needed to clarify the role of AChE abnormality in the formation of pathology changes in patients with Alzheimer's disease.

Endogenous opiates: 1991

This paper is the fourteenth installment of our annual review of research concerning the opiate system. It includes papers published during 1991 involving the behavioral, nonanalgesic, effects of the endogenous opiate peptides. The specific topics this year include stress; tolerance and dependence; eating; drinking; gastrointestinal and renal function; mental illness and mood; learning, memory, and reward; cardiovascular responses; respiration and thermoregulation; seizures and other neurological disorders; electrical-related activity; general activity and locomotion; sex, pregnancy, and development; immunological responses; and other behaviors.

Extrapyramidal signs in Alzheimer's disease: A 3-year follow-up study

Occurrence of extrapyramidal signs was investigated in a follow-up study of 32 patients with probable Alzheimer's disease (AD). Bradykinesia and rigidity were observed in 39% and 11% of the neuroleptic-free patients at entry and in 72% and 61% at year 3, respectively. Tremor was not a predominant feature nor did its occurrence increase over time. Use of neuroleptics contributed to extrapyramidal signs; 75-100% of the neuroleptic-treated patients showed bradykinesia, rigidity or orofacial dyskinesia. The homovanillic acid (HVA) concentrations of the cerebrospinal fluid at entry were comparable to those of age-matched controls. Nor did HVA levels correlate with rigidity or bradykinesia in these early AD cases. Presence of bradykinesia or rigidity at the initial evaluation predicted more severe dementia and a poor prognosis over the period of 3 years, although interaction of initial clinical severity of dementia was significant. Of 15 patients with these signs 3 (20%) died and 8 (53%) needed institutional care, while of 17 patients without these signs only 1 (6%) died and 2 (12%) were institutionalized by year 3 (p less than 0.01).

Neurochemical markers in the cerebrospinal fluid of patients with Alzheimer's disease, Parkinson's disease and amyotrophic lateral sclerosis and normal controls

Several neurotransmitter markers were investigated in the cerebrospinal fluid (CSF) from patients with Alzheimer's disease (AD) (n = 27), Parkinson's disease (PD) (n = 35) and ALS (n = 26) and from control subjects (n = 34) to compare the possible alterations in the biochemical profiles of these different neurodegenerative diseases. The main proportion of the patients represented an early phase of the illness at the time of the diagnosis. Correlations of the degree of dementia and the stage of the disease with CSF measures were evaluated. The CSF levels of somatostatin like-immunoreactivity (SLI) were significantly reduced in AD patients when compared with those of normals and ALS patients. The CSF concentrations of homovanillic acid (HVA) were significantly decreased for PD patients and the decrease focused on the non-demented patients. A trend of decreasing HVA values towards the most advanced stage of Parkinson's disease assessed by Webster's scale was also displayed. The content of 3-methoxy-4-hydroxyphenylglycol (MHPG) in the CSF was higher for ALS patients than for other groups. The lowest 5-hydroxy-indoleacetic acid (5HIAA) levels were observed in the PD group and the lowest acetylcholinesterase (AChE) activities were found in the PD patients with the most severe disease. Changes in CSF measures were too subtle to be beneficial for diagnostic purposes, but adequate for reflecting the different neurochemical profiles of these three degenerative neurological disorders.

The effects of noradrenergic neurotoxin, DSP-4, on the performance of young and aged rats in spatial navigation task

The present study investigated whether an overactive noradrenergic system is related to the impairment in learning/memory in aged subjects. The effects of partial noradrenaline depletion (using the noradrenergic neurotoxin DSP-4) on the acquisition of a water maze task was investigated in young and aged rats, and hippocampal noradrenaline content was correlated with spatial learning performance in similar rats. DSP-4 treatment impaired markedly the acquisition of the water maze task in aged rats, but improved it slightly in young rats. DSP-4 treatment decreased swimming speed, and this effect tended to be more marked in young rats. In the group of control rats, hippocampal noradrenaline tended to correlate positively with spatial bias in aged rats (the rats with the highest noradrenaline content in the hippocampus tended to have the best spatial learning/memory), but negatively in young rats. These results do not support the hypothesis that spatial learning/memory impairment is due to an overactive noradrenergic system in aged rats. Further studies are needed to clarify the reasons of the marked age-related difference in the effects of DSP-4 on the performance of water maze task in rats.

The molecular forms of acetylcholinesterase in cerebrospinal fluid of normal subjects--effect of aging

Acetylcholinesterase (AChE) activity is increased in human cerebrospinal fluid (CSF) during aging. The present study investigated whether the relative amounts of different molecular forms of CSF-AChE are also affected during aging. Thus, the CSF samples of healthy human subjects (age range 20-79 years, n = 23) were analyzed for sedimentation forms of AChE activity. Five different forms of AChe activity were detected in human CSF. The relative amount of tetrameric and dimeric globular forms, which are the main forms of AChE in CSF, were not related with age. Furthermore, the relative amount of monomeric globular and asymmetric forms which are minor forms of AChE in CSF did not seem to be related to age. Since total CSF-AChE activity is increased during aging, it seems to be due to the increased amounts of the tetrameric and dimeric forms of enzyme activity.