Cerebrospinal fluid levels of diazepam-binding inhibitor in neurodegenerative disorders with dementia

We investigated CSF levels of diazepam-binding inhibitor (DBI), a recently discovered neuropeptide that allosterically modulates GABAergic transmission, in various neurodegenerative disorders with dementia (28 patients with Parkinson's disease, 10 with Alzheimer's disease, 7 with Huntington's chorea). We applied a battery of neuropsychological tests to determine the degree of dementia and to exclude the presence of mood alterations. CSF DBI levels were elevated in parkinsonian subjects with dementia and in patients with Alzheimer's disease, but decreased in Huntington's chorea patients. We hypothesize that modifications of CSF DBI levels may be related to a functional or structural alteration of the GABAergic system.

CSF diazepam-binding inhibitor in alcoholics and normal controls

Diazepam-binding-inhibitor (DBI) and gamma-aminobutyric acid (GABA) are colocalized in neurons in the brain. This system has been implicated in anxiety and in the regulation of corticotropin-releasing hormone (CRH) secretion. Alcohol has direct and indirect effects on the functioning of GABAA receptors. Abstinent alcoholics are, on the average, more anxious than controls. In tests of animal behavior, DBI has anxiogenic, and alcohol has anxiolytic potency. Therefore, we compared alcoholic patients and healthy controls for cerebrospinal fluid (CSF) levels of DBI, and looked for a correlation between CSF levels of DBI and CRH. There was no significant difference in CSF concentrations of DBI between the two groups and no significant correlation between CSF DBI and our measure of anxiety. However, there was a significant positive correlation between CSF levels of DBI and CRH in both the alcoholic and control groups.

Cerebrospinal fluid monoamine metabolites and neuropeptides in patients with panic disorder

Concentrations of homovanillic acid (HVA), 5-hydroxyindoleacetic acid (5-HIAA), 3-methoxy-4-hydroxyphenylglycol (MHPG) as well as somatostatin (SRIF) and beta-endorphin (beta-END) were assayed in the cerebrospinal fluid (CSF) of 34 patients with panic disorder and of ten neurological controls. No aberrations of the monoaminergic or peptidergic variables measured were found in the nonpanic state of patients with panic disorder. A modest correlation (P = 0.04) between total anxiety scores and CSF MHPG was observed.

Neuropeptide K is present in human cerebrospinal fluid

Neurokinin A-like immunoreactivity (NKA-LI) in human cerebrospinal fluid (CSF) was determined by radioimmuno assay (RIA) combined with high performance liquid chromatography (HPLC). The major immunoreactive component did not coelute with NKA, but coeluted with neuropeptide K (NPK), which contains the NKA sequence in its C-terminus. Trypsin treatment of this component from human CSF and of synthetic NPK, produced a substance which coeluted with NKA in the HPLC system. When the NKA-LI was oxidized with hydrogen peroxide and rechromatographed, the immunoreactivity coeluted with NPK sulfoxide. The results indicate that the main part of the NKA-LI in CSF is identical with NPK. The mean concentration of NPK measured in CSF from 6 healthy subjects by HPLC-RIA was 23 +/- 11 (SD) pmol/L.

CSF GABA and neuropeptides in pathological gamblers and normal controls

We previously reported that pathological gamblers may have increased central noradrenergic activity. Neurons releasing gamma-aminobutyric acid (GABA) are known to be a part of an inhibitory system regulating the activity of central noradrenergic neurons. Therefore, we examined cerebrospinal fluid (CSF) levels of GABA in pathological gamblers and normal controls. There was no significant difference between the groups. Also, depressed and nondepressed gamblers did not differ significantly in their CSF levels of GABA. Among controls, however, there was a significant negative correlation between CSF levels of GABA and the norepinephrine metabolite 3-methoxy-4-hydroxyphenylglycol (MHPG) and a significant positive correlation between CSF levels of GABA and corticotropin releasing hormone (CRH). Also, CSF levels of CRH showed a significant positive correlation with CSF levels of adrenocorticotropic hormone in both pathological gamblers and controls.

Modulation of pain in fibromyalgia (fibrositis syndrome): cerebrospinal fluid (CSF) investigation of pain related neuropeptides with special reference to calcitonin gene related peptide (CGRP)

The cerebrospinal fluid (CSF) levels of calcitonin gene related peptide (CGRP) were 0.94 +/- 0.06 fmol/ml (mean +/- SEM), of substance P, 35.1 +/- 3.2 fmol/ml and of substance P (1-7), 10.8 +/- 1.2 fmol/ml, as measured by radioimmunoassay in 26 female patients with fibromyalgia. No correlation was found between the levels of CGRP and the substance P and substance P (1-7) levels (r = 0.316, p = 0.14). Our results show that the anatomical coexistence of pain related neuropeptides in neurons is not necessarily reflected by the levels of these peptides measured in the CSF. The presence of CGRP in the CSF could be important since it can enhance the nociceptive activity of tachykinins. This may be of importance in the pathogenesis of pain in fibromyalgia.

Hydrocephalus-induced changes in the composition of cerebrospinal fluid

Studies reporting the composition of cerebrospinal fluid obtained from hydrocephalic humans have been critically reviewed. Hydrocephalus-induced alterations in the cerebrospinal fluid concentrations of neurotransmitters and peptide neuromodulators, products of glycolysis and nucleotide metabolism, neural cell-derived proteins and enzymes, and serum-derived proteins have been documented. The data are interpreted with reference to experimental studies. The reported changes suggest that in the hydrocephalic brain there are disturbances of oxidative metabolism and neurotransmission, and perhaps damage to periventricular cells particularly when intracranial pressure is elevated. Although no assays have provided and entirely useful guide to aid decisions regarding shunt therapy, they have provided in vivo information regarding the pathophysiology of hydrocephalus.

Diazepam-binding inhibitor and corticotropin-releasing hormone in cerebrospinal fluid

Diazepam-binding inhibitor (DBI) is a neuromodulatory peptide for gamma-aminobutyric acid (GABA) neurotransmission. Cerebrospinal fluid (CSF) levels of DBI have been found to be elevated in depression. CSF levels of the peptide corticotropin-releasing hormone (CRH) have also been found to be elevated in depression. Therefore, we examined for a relationship between DBI and CRH in human CSF. We found significant positive correlations between CSF levels of DBI and CRH in depressed patients, pathological gamblers, and normal controls. These data, along with the elevated CSF levels of DBI in depression, suggest the possibility that DBI may have a role in coordinating responses to stress in humans in addition to its possible role in the pathophysiology of depression.

Cerebrospinal fluid content of diazepam binding inhibitor in chronic hepatic encephalopathy

The neuropeptide diazepam binding inhibitor (DBI) is an endogeneous allosteric modulator of gamma-aminobutyric acid (GABA) receptors at the benzodiazepine recognition site. Recent theories on the neurochemical cause for hepatic encephalopathy have implicated activation of inhibitory neurotransmitter GABA systems. In 20 patients with hepatic disease, blood and cerebrospinal fluid (CSF) levels of ammonia and amino acids were measured. As in previous studies there was a selective elevation of CSF amino acids as well as a correlation between CSF glutamine levels and encephalopathy. CSF DBI levels were maximally elevated 5-fold in patients with hepatic encephalopathy, but they were normal in those patients with liver disease not associated with changes in mental status and in patients with nonhepatic encephalopathy. Levels of DBI correlated with the clinical staging of hepatic encephalopathy. These data suggest that DBI may participate in the modulation of cerebral function in hepatic encephalopathy.

Pituitary protein 7B2-like immunoreactivity in cerebrospinal fluid: comparison with other neuropeptides

A pituitary protein, designated 7B2, was demonstrated to be present in the cerebrospinal fluid (CSF) obtained from control subjects and patients with various cerebrovascular accidents (CVAs). Although there was not any significant difference in mean immunoreactive 7B2 concentrations among various CVA groups, the CSF immunoreactive 7B2 levels in control subjects were 10 to 100 times higher than those in control plasma samples. Immunoreactive calcitonin gene-related peptide (CGRP) and immunoreactive atrial natriuretic peptide (ANP) levels in the CSF were comparable to those in corresponding normal plasma samples. The CSF ANP concentrations in patients with cerebral bleeding and subarachnoid hemorrhage were significantly lower than those in control subjects. Gel chromatography or high-performance liquid chromatography indicated that the main immunoreactivities of 7B2, CGRP, and ANP coeluted with corresponding standard material. The high CSF concentrations of immunoreactive 7B2 observed might indicate a functional role of 7B2 in the central nervous system.

Diazepam binding inhibitor-like immunoreactivity (DBI-LI) in human CSF. Correlations with neurological disorders

Cerebrospinal fluid (CSF) levels of the anxiogenic neuropeptide diazepam binding inhibitor (DBI) were determined by radioimmunoassay in 281 patients who underwent evaluation for neurological problems. Serial dilution curves and reverse-phase high pressure liquid chromatography showed that the immunoreactive material in CSF behaved just as authentic DBI extracted from human brain. Furthermore in the assay there was no evidence of interference from CSF samples deprived of DBI by immunoaffinity. In 82 patients with no evidence of major lesions in the central nervous system, who acted as controls, the CSF DBI content was shown to be age- and sex-related. No correlation was observed with the CSF protein concentration. In patients with different types of dementia, the levels of CSF DBI were significantly increased in a group with normal pressure hydrocephalus. No significant differences were found between Alzheimer's disease, multi-infarct dementia, or dementia with Parkinson's disease and controls. In non-demented patients with Parkinson's disease the levels of DBI were increased in a subgroup with depressive disturbances whereas no differences was observed in the non-depressed cases. The content of DBI was markedly reduced in 5 cases with olivopontocerebellar atrophy and in 4 with spinocerebellar ataxia. In all the other disorders studied the levels of DBI were similar to or slightly lower (multiple sclerosis) than those of the controls. The origin of DBI in cerebrospinal fluid is uncertain; a number of various possibilities are discussed concerning the proposed role of DBI as modulator of brain GABAergic transmission.

Characteristics of cerebrospinal fluid neuropeptides relevant to clinical research

Studies of human cerebrospinal fluid (CSF) peptides were conducted in an attempt to broaden the utility of CSF peptide determinations in psychiatric research. Healthy volunteers had two lumbar punctures, at least 3 weeks apart, to assess reproducibility within subjects. CSF levels of eight peptides were reliably reproducible, indicating that longitudinal studies of these CSF neuropeptides are feasible. Levels of 10 peptides were determined in four sequential 8 ml aliquots of CSF. CSF rostrocaudal gradients were not found for any of these 10 peptides. Neuropeptide Y (NPY), growth hormone releasing factor (GHRF), and corticotropin releasing factor (CRF) were measured in CSF from twins and brothers. CSF NPY levels were heritable, while CRF and GHRF levels were influenced more by environment. CSF levels of CRF, beta-lipotropin, vasoactive intestinal peptide, adrenocorticotropic hormone, and somatostatin were highly correlated with one another, suggesting that a common factor is responsible for a significant proportion of the observed variance in their CSF levels. These results suggest that CSF peptide measurements may have a broad range of applicability to clinical psychiatric research.

Histochemistry of proteases in ependyma, choroid plexus and leptomeninges

Aminopeptidase M (APM), aminopeptidase A (APA), dipeptidyl peptidase IV (DPP IV) and gamma-glutamyl transferase (GGT) were demonstrated histochemically in cryostat sections of the rat brain to show the reaction pattern of ependyma, choroid plexus and leptomeninges. GGT was only demonstrable in the cell membranes of ependymal cells and in the leptomeninges; however, APA, APM and DAP IV showed a variable degree of activity in the capillary endothelium of the choroid plexus as well as in the leptomeninges. On the basis of these results, it is postulated that peptides in the cerebrospinal fluid can be cleaved extraventricularly by the enzymes demonstrated in the leptomeninges.

Human brain calcitonin gene-related peptide (CGRP) is concentrated in the locus caeruleus

A quantitative survey of calcitonin gene-related peptide (CGRP) in brain, peripheral nerve and cerebrospinal fluid (CSF) was performed using radioimmunoassay (RIA) with antiserum against synthetic hCGRP. High levels (approximately 2000-15,000 fmol/mg protein) were found in the dorsal spinal cord, dorsal nerve and trigeminal nerve. Relatively large amounts (500-2000) were found in parts of the hypothalamic-pituitary axis, peripheral nerve and, for the first time, in the locus caeruleus. Low levels of CGRP (less than 500) were detected in the cerebrum, subcortical nuclei and cerebellum. CGRP, not previously reported in CSF, was detectable in all of 27 CSF specimens with mean values of 30 +/- 4.5 pmol/L (SE). Simultaneous plasma CGRP levels were higher and, when elevated by antihypertensive treatment were not increased in CSF, just as astronomical plasma levels of calcitonin in medullary carcinoma of the thyroid are not reflected in CSF. Our data confirm and extend the results of previous human and animal studies with evidence of species variation: humans have low CGRP levels in subcortical nuclei whereas high levels have been found in rat caudate-putamen and amygdala. The high level of CGRP in the locus caeruleus, the major source of noradrenergic neurotransmission in the CNS, is in harmony with the presumed functions of the LC and the very potent hemodynamic activity of CGRP.

The presence of calcitonin gene-related peptide in human cerebrospinal fluid

This study demonstrates the presence of calcitonin gene-related peptide (CGRP) in human cerebrospinal fluid (CSF) using specific and sensitive radioimmunoassay, together with gel-permeation and high performance liquid chromatography (HPLC). The median immunoreactive CGRP (i-CGRP) level from 158 CSF specimens was 8.0 pmol/l, as measured with an antiserum recognizing the whole molecule of CGRP (CC-2/1) and 12.0 pmol/l with an antiserum recognizing the C-terminal region of CGRP (CG-39). CSF samples with high protein concentration (greater than or equal to 0.6 g/l) had a median level of i-CGRP of 18.4 pmol/l when measured with antiserum CC-2/1 and 23.0 pmol/l with CG-39, while samples with 'normal' protein concentrations (less than 0.6 g/l) had much lower values, with median levels of 7.0 and 11.0 pmol/l, with the two antisera, respectively. Gel-permeation chromatography and HPLC studies revealed multiple peaks of i-CGRP, consistent with forms with different molecular weights. However, on HPLC, the major peak of i-CGRP corresponded to the elution position of the synthetic hCGRP(1-37) and was able to bind to a CGRP specific receptor preparation suggesting that it may be biologically active.

Reversed-phase high-performance liquid chromatographic-radioreceptor assay of human cerebrospinal fluid neuropeptides. Maximizing recovery of picomoles of peptides and minimizing memory

Reversed-phase high-performance liquid chromatography (RP-HPLC) is used to analyze neuropeptides in human cerebrospinal fluid (CSF) obtained from patients suffering from lower-back pain. Because CSF contains only femtomole to picomole amounts of those peptides, it is important to minimize any sample memory effect, while maximizing peptide recovery and avoiding any potential artifactual peak formation during chromatography. This study describes the phenomenon of active site occupancy by peptides on the RP-HPLC column, which is crucial when studying CSF where femtomole to picomole amounts of neuropeptides could be lost. Knowledge of those basic chromatographic factors is important whenever biologic extracts of peptides are applied to and eluted from an RP-HPLC column and then detected off-line with a radioreceptor assay, which is sensitive at the picomole level.

[Radioimmunoassay of the calcitonin gene-related peptide and its measurement in the plasma of patients with medullary thyroid carcinoma and in the cerebrospinal fluid of normal subjects]

Calcitonin gene-related peptide (CGRP) is a peptide recently found by recombinant DNA and molecular biological techniques in rat medullary thyroid carcinoma cells, but its physiological role(s) is unknown. We established a radioimmunoassay for this peptide using human-CGRP (1-37) as a standard, 125I-human-CGRP (1-37) as a tracer, and anti-rat-CGRP (28-37) serum as a first antibody. Aprotinin, an inhibitor of proteolytic enzymes in the plasma, was also added to the assay system, because in its absence the tracer was degraded during incubation with plasma samples. The sensitivity of the assay was 60 pg/ml and the intra- and inter-assay coefficients of variation were 6.0% and 8.5%, respectively. The recovery was 105 +/- 17%. The plasma levels of CGRP in 17 normal subjects (mean +/- S.D. age, 45 +/- 12 years) were all below 300 pg/ml, the mean level being 132 +/- 77 pg/ml. The levels were also below 300 pg/ml in 20 of 21 patients with medullary thyroid carcinoma, but one patient who had a high level of 942 pg/ml (mean value, 142 +/- 193 pg/ml). There was no significant difference between the mean plasma levels of CGRP in normal subjects and patients with medullary thyroid carcinoma. The mean plasma levels of CGRP in 5 patients with medullary thyroid carcinoma did not increase in response to infusion of either 4.3 mg/kg of calcium in 10 minutes or 4 micrograms/kg of tetragastrin in 5 minutes, although the plasma levels of calcitonin in these patients increased markedly during these provocation tests. The levels of CGRP in the cerebrospinal fluid of 16 normal volunteers were all below the detectable limit (less than 60 pg/ml). These findings suggest that fewer patients with medullary thyroid carcinoma than reported previously have high plasma levels of CGRP, either in the basal state or in response to calcium or gastrin, and that the levels of CGRP in the cerebrospinal fluid of normal subjects are very low.

Neurotensin-like immunoreactivity (NTLI) concentration in the cerebrospinal fluid of children and its alteration in a febrile aseptic meningitis

Neurotensin-like immunoreactivity (NTLI) concentrations in the cerebrospinal fluid (CSF) of normal children and patients with febrile aseptic meningitis, aged 7 months to 15 years, were studied. The NTLI concentrations in CSF of 27 children with normal CSF findings were 160.1 +/- 54.6 pg/ml (mean +/- S.D.). The NTLI concentration in CSF of 26 patients in an acute phase of aseptic meningitis was 110.6 +/- 51.1 pg/ml which was significantly (P less than 0.01) lower than the controls. These patients had a mean temperature of 101.4 +/- 1.5 degrees F which remained elevated for an average of 3.5 days. The NTLI concentrations in CSF of 23 patients in a recovery phase (after blood and CSF findings became normal with no fever) were 166.5 +/- 57.8 pg/ml, which did not differ significantly from the normal. There were no statistical correlations between the NTLI concentration in CSF and the protein concentration or total cell count in CSF. These results suggest that NTLI concentration changes during a febrile aseptic meningitis and that it may be associated with thermoregulation.