Circadian rhythm in cerebrospinal fluid noradrenaline of man and monkey

Circadian Rhythms of the Blood-Brain Barrier and Drug Delivery

The blood-brain barrier (BBB) is a critical interface separating the central nervous system from the peripheral circulation, ensuring brain homeostasis and function. Recent research has unveiled a profound connection between the BBB and circadian rhythms, the endogenous oscillations synchronizing biological processes with the 24-hour light-dark cycle. This review explores the significance of circadian rhythms in the context of BBB functions, with an emphasis on substrate passage through the BBB. Our discussion includes efflux transporters and the molecular timing mechanisms that regulate their activities. A significant focus of this review is the potential implications of chronotherapy, leveraging our knowledge of circadian rhythms for improving drug delivery to the brain. Understanding the temporal changes in BBB can lead to optimized timing of drug administration, to enhance therapeutic efficacy for neurological disorders while reducing side effects. By elucidating the interplay between circadian rhythms and drug transport across the BBB, this review offers insights into innovative therapeutic interventions.

Resting-State fMRI Study of Vigilance Under Circadian and Homeostatic Modulation Based on Fractional Amplitude of Low-Frequency Fluctuation and Regional Homogeneity in Humans Under Normal Entrained Conditions

BACKGROUND

How brain neural activity changes at multiple time points throughout the day and the neural mechanisms underlying time-dependent modulation of vigilance are less clear.

PURPOSE

To explore the effect of circadian rhythms and homeostasis on brain neural activity and the potential neural basis of time-dependent modulation of vigilance.

STUDY TYPE

Prospective.

SUBJECTS

A total of 30 healthy participants (22-27 years old).

FIELD STRENGTH/SEQUENCE

A 3.0 T, T1-weighted imaging, echo-planar functional MRI (fMRI).

ASSESSMENT

Six resting-state fMRI (rs-fMRI) scanning sessions were performed at fixed times (9:00 h, 13:00 h, 17:00 h, 21:00 h, 1:00 h, and 5:00 h) to investigate fractional amplitude of low-frequency fluctuation (fALFF) and regional homogeneity (ReHo) diurnal variation. The fALFF/ReHo and the result of the psychomotor vigilance task were used to assess local neural activity and vigilance.

STATISTICAL TESTS

One-way repeated measures analysis of variance (ANOVA) was used to assess changes in vigilance (P < 0.05) and neural activity in the whole brain (P < 0.001 at the voxel level and P < 0.01 at the cluster level, Gaussian random field [GRF] corrected). Correlation analysis was used to examine the relationship between neural activity and vigilance at all-time points of the day.

RESULTS

The fALFF/ReHo in the thalamus and some perceptual cortices tended to increase from 9:00 h to 13:00 h and from 21:00 h to 5:00 h, whereas the key nodes of the default mode network (DMN) tended to decrease from 21:00 h to 5:00 h. The vigilance tended to decrease from 21:00 h to 5:00 h. The fALFF/ReHo in the thalamus and some perceptual cortices was negatively correlated with vigilance at all-time points of the day, whereas the fALFF/ReHo in the key nodes of the DMN was positively correlated with vigilance.

DATA CONCLUSION

Neural activities in the thalamus and some perceptual cortices show similar trends throughout the day, whereas the key nodes of the DMN show roughly opposite trends. Notably, diurnal variation of the neural activity in these brain regions may be an adaptive or compensatory response to changes in vigilance.

EVIDENCE LEVEL

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TECHNICAL EFFICACY

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Brain Mechanisms of COVID-19-Sleep Disorders

2020 and 2021 have been unprecedented years due to the rapid spread of the modified severe acute respiratory syndrome coronavirus around the world. The coronavirus disease 2019 (COVID-19) causes atypical infiltrated pneumonia with many neurological symptoms, and major sleep changes. The exposure of people to stress, such as social confinement and changes in daily routines, is accompanied by various sleep disturbances, known as 'coronasomnia' phenomenon. Sleep disorders induce neuroinflammation, which promotes the blood-brain barrier (BBB) disruption and entry of antigens and inflammatory factors into the brain. Here, we review findings and trends in sleep research in 2020-2021, demonstrating how COVID-19 and sleep disorders can induce BBB leakage via neuroinflammation, which might contribute to the 'coronasomnia' phenomenon. The new studies suggest that the control of sleep hygiene and quality should be incorporated into the rehabilitation of COVID-19 patients. We also discuss perspective strategies for the prevention of COVID-19-related BBB disorders. We demonstrate that sleep might be a novel biomarker of BBB leakage, and the analysis of sleep EEG patterns can be a breakthrough non-invasive technology for diagnosis of the COVID-19-caused BBB disruption.

Adrenergic Signaling in Circadian Control of Immunity

Circadian rhythms govern a multitude of physiologic processes, both on a cell-intrinsic level and systemically, through the coordinated function of multi-organ biosystems. One such system-the adrenergic system-relies on the catecholamine neurotransmitters, adrenaline and noradrenaline, to carry out a range of biological functions. Production of these catecholamines is under dual regulation by both neural components of the sympathetic nervous system and hormonal mechanisms involving the hypothalamus-pituitary-adrenal axis. Importantly, both neural and hormonal arms receive input from the body's central clock, giving rise to the observed rhythmic variations in catecholamine levels in blood and peripheral tissues. Oscillations in catecholamine signals have the potential to influence various cellular targets expressing adrenergic receptors, including cells of the immune system. This review will focus on ways in which the body's central master clock regulates the adrenergic system to generate circadian rhythms in adrenaline and noradrenaline, and will summarize the existing literature linking circadian control of the adrenergic system to immunologic outcomes. A better understanding of the complex, multi-system pathways involved in the control of adrenergic signals may provide immunologists with new insight into mechanisms of immune regulation and precipitate the discovery of new therapeutics.

Regulation of the Blood-Brain Barrier by Circadian Rhythms and Sleep

The blood-brain barrier (BBB) is an evolutionarily conserved, structural, and functional separation between circulating blood and the central nervous system (CNS). By controlling permeability into and out of the nervous system, the BBB has a critical role in the precise regulation of neural processes. Here, we review recent studies demonstrating that permeability at the BBB is dynamically controlled by circadian rhythms and sleep. An endogenous circadian rhythm in the BBB controls transporter function, regulating permeability across the BBB. In addition, sleep promotes the clearance of metabolites along the BBB, as well as endocytosis across the BBB. Finally, we highlight the implications of this regulation for diseases, including epilepsy.

Disciplined sleep for healthy living: Role of noradrenaline

Sleep is essential for maintaining normal physiological processes. It has been broadly divided into rapid eye movement sleep (REMS) and non-REMS (NREMS); one spends the least amount of time in REMS. Sleep (both NREMS and REMS) disturbance is associated with most altered states, disorders and pathological conditions. It is affected by factors within the body as well as the environment, which ultimately modulate lifestyle. Noradrenaline (NA) is one of the key molecules whose level increases upon sleep-loss, REMS-loss in particular and it induces several REMS-loss associated effects and symptoms. The locus coeruleus (LC)-NAergic neurons are primarily responsible for providing NA throughout the brain. As those neurons project to and receive inputs from across the brain, they are modulated by lifestyle changes, which include changes within the body as well as in the environment. We have reviewed the literature showing how various inputs from outside and within the body integrate at the LC neuronal level to modulate sleep (NREMS and REMS) and vice versa. We propose that these changes modulate NA levels in the brain, which in turn is responsible for acute as well as chronic psycho-somatic disorders and pathological conditions.

Predictors of plasma and urinary catecholamine levels in normotensive and hypertensive men and women

Age, sex, hypertension and dietary sodium are proposed to affect plasma and urinary catecholamines. Yet no prior study has examined the simultaneous effects of these factors within the same study population, so results may have been confounded by factors not determined. We investigate, for the first time, the impact of simultaneously determined predictors of plasma and urinary catecholamines, and the relationship of catecholamines with the diagnosis of hypertension. Hypertensive and normotensive subjects (n=308) were studied off antihypertensives in liberal and low sodium balance. Twenty-four hour urinary catecholamines (norepinephrine and epinephrine) were measured. Plasma catecholamines were measured supine after overnight fast. Repeated measures multivariate linear regression models examined effect of sex, race, age, body mass index, dietary salt (liberal salt vs. low salt), hypertension status, and mean arterial pressure on plasma and urinary catecholamines. Logistic regression determined the relationship of catecholamines with diagnosis of hypertension. Dietary sodium restriction and increasing age predicted increased plasma and urinary norepinephrine, with sodium restriction having greatest effect. Female sex predicted lower urinary and plasma epinephrine. Neither plasma nor urinary catecholamines predicted the diagnosis of hypertension. In summary, specific demographic factors variably impact catecholamines and should be considered when assessing catecholamines in research and clinical settings.

Blood Pressure in Middle-Aged Women: A Comparison Between Office-, Self-, and Ambulatory Recordings

A blood pressure screening was carried out in women aged 40-64 years in a geographically defined area in southern Sweden; the attendance was 72%. Middle-aged women classified as normotensives by standard criteria were found to differ from hypertensives also when blood pressure was recorded with non-invasive ambulatory technique; this was so when calculated for day, night, and 24 hours. The frequency of ambulatory blood pressure values > or = 140/90 mmHg was also significantly lower in normotensives than in hypertensives. The established way of diagnosing hypertension and normotension thus correlated well with the results of ambulatory monitoring in women. Furthermore, women had their highest blood pressure in the late afternoon and not in the mornings, as previously shown in men. This was so in all three groups of women (normotensives, borderline hypertensives, and hypertensives). This difference leaves room for speculation about different types of stress load during the day in men and women.

Chronopharmaceutics: gimmick or clinically relevant approach to drug delivery?

Due to advances in chronobiology, chronopharmacology, and global market constraints, the traditional goal of pharmaceutics (e.g. design drug delivery systems with a constant drug release rate) is becoming obsolete. However, the major bottleneck in the development of drug delivery systems that match the circadian rhythm (chronopharmaceutical drug delivery systems: ChrDDS) may be the availability of appropriate technology. The last decade has witnessed the emergence of ChrDDS against several diseases. The increasing research interest surrounding ChrDDS may lead to the creation of a new sub-discipline in pharmaceutics known as chronopharmaceutics. This review introduces the concept of chronopharmaceutics, addresses theoretical/formal approaches to this sub-discipline, underscores potential disease-targets, revisits existing technologies and examples of ChrDDS. Future development in chronopharmaceutics may be made at the interface of other emerging disciplines such as system biology and nanomedicine. Such novel and more biological approaches to drug delivery may lead to safer and more efficient disease therapy in the future.

Dopamine and noradrenaline efflux in the prefrontal cortex in the light and dark period: effects of novelty and handling and comparison to the nucleus accumbens

We used on-line microdialysis measurements of dopamine and noradrenaline extracellular concentrations in the medial prefrontal cortex of awake, freely moving rats during the dark and the light period of the day to study whether (i) basal efflux would be higher in the active, dark period than in the inactive, light period; (ii) the activation induced by environmental stimuli would be dependent on these conditions. When determined one day after cannula placement, noradrenaline and dopamine levels were higher during the dark. Maximal relative increases induced by novelty and handling were 150% and 175-200%, respectively, and were very similar in the light and the dark, but the net increases were higher in the dark. Separate groups were tested one week after cannula placement to ensure recovery of possibly disturbed circadian rhythms. While basal levels in the dark were now approximately twice those in the light, the maximal relative and net increases after both novelty and handling were very similar. Basal levels of dopamine in the nucleus accumbens (one day after cannula placement) were not different in the light or dark, but were increased by novelty and handling to about 130% only in the light period, not in the dark. Thus, in the prefrontal cortex, dopamine strongly resembles noradrenaline, in that basal efflux was state dependent, whereas activation by stimuli was not. In the nucleus accumbens, basal dopamine efflux was not state dependent, but activation by stimuli was. These results suggest that there are differential effects of circadian phase on basal activity and responsiveness of the mesolimbic vs the mesocortical dopamine system.

Monoamine metabolites in 'leftover' newborn human cerebrospinal fluid--a potential resource for biobehavioral research

Although variations in monoamine neurotransmission have been implicated in a variety of psychopathologic outcomes in man, little is known about how monoamines influence or are affected by developmental processes early in childhood. In this study, assays for 5-hydroxyindoleacetic acid (5-HIAA), homovanillic acid (HVA), and 3-methoxy-4-hydroxyphenylglycol (MHPG) were obtained from leftover cerebrospinal fluid (CSF) of 119 human newborns. The levels of these monoamine metabolites were in keeping with pre-existing 'normative' data from two small previously published studies. The levels were largely unaffected by variations in the infants' physiologic condition at the time of lumbar puncture, and exhibited evidence for circadian rhythms. Among 32 infants (8 neurologically normal, 24 neurologically compromised) for whom more than one CSF sample was obtained during the first year of life, the correlations between baseline and follow-up measurements for 5-HIAA and HVA were on the order of 0.75. Correlations between twins (four sets) were significantly higher than those between unrelated individuals for 5-HIAA and HVA. At 9-month follow-up, neurologically normal infants in the lower extreme 15% of the distribution for 5-HIAA exhibited a trend toward lower scores for sociability on the Colorado Childhood Temperament Inventory (maternal report) than their counterparts at the upper extreme of the 5-HIAA distribution. Leftover CSF is a readily available resource for measurements of monoamine metabolites (and possibly other CSF constituents) in population-based samples of human newborns.

Disruption of circadian MHPG rhythmicity in major depression

Plasma concentrations of total (free plus conjugated) 3-methoxy-4-hydroxyphenylglycol (MHPG) were determined every 3 hr for a 24-hr period in 32 unipolar depressed patients, 11 bipolar depressed patients, and 12 healthy subjects. Each subject's circadian MHPG rhythmicity was modeled by a sinusoidal function. Temporal parameters were estimated by linear least squares regression with a fixed 24-hr period. The variabilities associated with estimates of circadian amplitude and acrophase were roughly twice as large in the patients compared to healthy subjects. Phase advances were associated most significantly with the agitated rather than the retarded subtype of depression, and with first episode depressions. Treatment with desipramine (n = 26) did not alter significantly any of the model parameters and had no effect on circadian variability in any patient group. The data overall support a dysregulation theory for depressive illness with phase advances representing one manifestation of such dysregulation.

Effect of pregnancy and pain on cerebrospinal fluid immunoreactive enkephalins and norepinephrine in healthy humans

Endogenous spinal opioid or noradrenergic system activation may increase pain threshold during pregnancy and following a painful stress. Variation in spinal antinociceptive activity is also postulated to explain in part the large variability in postoperative opioid analgesic requirements. In this study, spinal noradrenergic and opioid activity, as reflected by the CSF concentrations of norepinephrine and immunoreactive enkephalins (total enkephalin-containing peptides), was determined in 58 women prior to surgery. The CSF concentration of these substances did not differ between pregnant and non-pregnant women. CSF norepinephrine tended to be greater in pregnant women who had experienced painful labor than in those who had not (1240 +/- 300 vs. 570 +/- 160 pmol/l; P = 0.056) and these women self-administered less morphine following cesarean section than those without labor pain (64 +/- 4 vs. 86 +/- 7 mg/24 h; P less than 0.01). However, CSF concentration of norepinephrine or immunoreactive enkephalins did not correlate with postoperative morphine use. These results suggest that spinal immunoreactive enkephalin and noradrenergic activity are not increased during pregnancy. However, pain may activate spinal noradrenergic pathways affecting pain sensation.

The influence of physical activity and posture on the antidepressant effect of sleep deprivation in depressed patients

A possible role of the factors 'physical activity' and 'posture' in the antidepressant effect of a total night's sleep deprivation (TSD) was investigated in 30 patients with major depressive disorder. Fifteen patients underwent TSD under 'conventional' conditions, while the other 15 were kept in bed during TSD but were not permitted to sleep. There was no significant difference between the antidepressant effects of TSD in the two groups. This result suggests that it is wakefulness itself rather than changes in physical activity or posture that is involved in the mechanism of the antidepressant action of TSD.

Hippocampal Noradrenaline and Serotonin Release over 24 Hours as Measured by the Dialysis Technique in Freely Moving Rats: Correlation to Behavioural Activity State, Effect of Handling and Tail-Pinch

Hippocampal extracellular levels of noradrenaline (NA), 5-hydroxytryptamine (5-HT), and 5-hydroxyindoleacetic acid (5-HIAA) were monitored with the microdialysis technique in freely moving rats. In one experiment 30 min samples were collected during 24 h of continuous perfusion, and the monoamine output was compared to the behavioural activity state, as arbitrarily classified in three categories: sleep/rest, drowsiness and full alertness associated with complex behaviours. In the individual animal the hippocampal NA and 5-HT output showed pronounced fluctuations during the 24 h period, but the 30 min sampling times did not allow for a clear-cut correlation to behavioural activity state. However, the mean NA and 5-HT output for all animals during the dark period of the day was 43 and 38% higher, respectively, than during the light period, and the average NA and 5-HT levels in samples collected during periods of high behavioural activity was 34 and 45% higher, respectively, than during periods of rest or sleep. In contrast, there were no detectable changes in extracellular 5-HIAA. The selective serotonin uptake blocker indalpine, added to the perfusion fluid at 1 microM, increased the extracellular 5-HT levels 6-fold, with a similar correlation to behavioural activity state as without indalpine. In a second experiment the effect of handling and tail-pinch was studied in 15 min sample fractions. Gentle handling of the animals during the sampling period increased the hippocampal NA and 5-HT output by 32 and 72%, respectively, and a similar increase (63 and 48%) was obtained by application of tail-pinch. Maximum NA output was reached during the handling or tail-pinch period, whereas maximal 5-HT levels were detected in the subsequent 15 min sample fraction. No changes in extracellular 5-HIAA was observed. It is concluded (1) that intracerebral microdialysis provides a useful method for the study of extracellular NA and 5-HT in the hippocampal formation of conscious rats during active behaviour; (2) that there are substantial fluctuations in hippocampal NA and 5-HT output in freely moving rats which correlate with the light - dark cycle as well as with the activity state of the animals; (3) that the spontaneous variations in 5-HT output are maintained during reuptake blockade; and (4) that behavioural activation through gentle handling or tail-pinch elicits NA and 5-HT release. The present data support a role of the forebrain NA and 5-HT systems in behavioural state control and highlights the necessity of experimental designs in which the spontaneous fluctuations in transmitter release are controlled for in studies of, for example, drug effects on NA and 5-HT release in conscious animals.

Diurnal fluctuation in levels of histamine metabolites in cerebrospinal fluid of rhesus monkey

In samples of ventricular cerebrospinal fluid (CSF) that were collected from a conscious, restrained rhesus monkey at intervals of 30 90 min, levels of the histamine metabolites, tele-methylhistamine (t-MH) and tele-methylimidazoleacetic acid (t-MIAA), were determined by gas chromatography-mass spectrometry. Levels of t-MH and t-MIAA each showed time-related fluctuations. Peak and trough concentrations of t-MIAA, the product of t-MH, paralleled, but lagged about 2 h behind, the levels of t-MH. Within the first 3 h of illumination, metabolite levels increased more than 3-fold; they fell sharply within the first 3 h of darkness. Mean levels of t-MH and t-MIAA were significantly higher during periods of illumination than of darkness. Fluctuations in the levels of pros-methylimidazoleacetic acid (p-MIAA), an endogenous isomer of t-MIAA that is not a histamine metabolite, were markedly different from those of t-MH or t-MIAA; p-MIAA levels peaked only at the middle of the dark period. The time-related fluctuations in levels of t-MH and t-MIAA, but not p-MIAA, are similar to the daily rhythmic changes observed in monkey CSF for the levels of other central neurotransmitters and peptide neurohormones.

Diurnal alterations of catecholamines, indoleamines and their metabolites in specific brain regions of the mouse

1. The diurnal variations of regional brain concentrations of dopamine (DA), norepinephrine (NE), serotonin (5-HT) and metabolites were determined in unperturbed male CD-1 mice. Determinations were made every 4 hr for 24 hr. 2. The most striking and significant variations in biogenic amines were seen in the hypothalamus, where concentrations of NE, DA and 5-HT varied in a rhythmic pattern and as much as two-fold during this period. 3. In some cases, daily alterations in parent biogenic amines were reflected by concurrent changes in their metabolites. 4. Since concentrations of neurotransmitters in the brain are often used as an indicator of stress and/or toxicity, these data should provide an accurate data base allowing for more accurate interpretation of results.

Circadian rhythms and contents of catechols in different brain structures, peripheral organs and plasma of the Atlantic cod, Gadus morhua

Diurnal variations in the concentrations of the catechols (CA) L-DOPA (LD), dopamine (DA), noradrenaline (NA), adrenaline (A) and DOPAC were determined in different brain parts, peripheral organs and plasma of the Atlantic cod, Gadus morhua, over a 24-hr period of artificial standard laboratory conditions and natural light (dark interval: 22.11-04.14). Three to four fishes were captured at 3-hourly intervals and killed by breaking their necks. The organs were dissected out and prepared using the alumina extraction procedure and subsequently analysed in an HPLC-system with electrochemical detection. In the brain structures (telencephalon, optic lobes, medulla oblongata + pons and hypothalamus), the CA levels showed a bimodal pattern with peaks at 16.00-19.00 and 07.00. The catecholamines (CAM) DA, NA and A exhibited the same pattern in the spleen, while NA and A in the heart and NA in plasma varied in a trimodal rhythm with peaks at 19.00, 01.00-04.00 and 07.00. The distribution of CAs and ratios of CAMs in the various brain structures, peripheral organs and plasma are given. The mean concentrations were calculated from the mean of eight groups of cod, taken over a 24-hr period. The results obtained are discussed in relation to the activity pattern of the cod and the differences in CA levels and rhythms between central structures, peripheral organs and plasma of the cod are discussed in relation to other studies on CA levels and rhythmic variations of CAs in related animals.

Effects of propranolol, clonidine and hydrochlorothiazide treatment and abrupt discontinuation on central and peripheral noradrenergic activity in essential hypertension

This study was undertaken to investigate further the CNS actions of commonly employed antihypertensive drugs. Measurements of cerebrospinal fluid (CSF) and plasma catecholamines (CA) were made in an attempt to estimate the activity of central and peripheral noradrenergic neurons during treatment with or after abrupt discontinuation of treatment with clonidine (CLO), propranolol (PRO), hydrochlorothiazide (HCTZ) or placebo, in patients with essential hypertension. A randomized, parallel, placebo-controlled, single-blind design was employed. BP reductions equal to or greater than 10 mmHg were observed with CLO (0.36 +/- 0.07 mg daily), PRO (160 mg +/- 0 mg daily) or HCTZ (70 +/- 12 mg daily). CLO reduced plasma norepinephrine (NE) by 64% and PRO increased it by 25%. Neither HCTZ nor placebo modified plasma NE. Plasma renin activity (PRA) was reduced by PRO (51%, P less than 0.01) and CLO (35%, P less than 0.05). CSF-NE levels (pg/ml) were significantly lower in the CLO group (CLO: 175 +/- 23; PRO: 278 +/- 35; HCTZ: 255 +/- 34; placebo: 203 +/- 7).

Circadian covariation of norepinephrine and serotonin in the locus coeruleus and dorsal raphe nucleus in the rat

We report robust correlations between concentrations of the neurotransmitters norepinephrine and serotonin in the locus coeruleus and the dorsal raphe nucleus of the brainstem in rats analyzed at 7 different time points over 24 h. We found similar circadian rhythmicities for both monoamines with acrophases just before the onset of the dark period. The monoamine concentrations diminished and the significant intercorrelation between norepinephrine and serotonin in the locus coeruleus disappeared during the night suggestive of a noradrenergic stimulation of dorsal raphe serotonin during the day. Timing of experiments is crucially important in studies on brain monoaminergic indices and their interrelationships.

Effects of clonidine on central and peripheral nerve tone in primary hypertension

To define the mechanisms whereby clonidine lowers blood pressure, we measured cerebrospinal fluid and plasma levels of norepinephrine, normetanephrine, epinephrine, dopamine, and the dopamine metabolite homovanillic acid in 10 primary hypertensive subjects before and after 3 months of clonidine treatment (mean dose, 0.68 mg/day). Catecholamines were measured by radioenzymatic methods. Cerebrospinal fluid and plasma sampling was performed after subjects had fasted and remained supine overnight, and plasma sampling was repeated 2 hours later, after subjects had ambulated. Supine and upright blood pressure fell, as might be expected. Cerebrospinal fluid levels of norepinephrine and normetanephrine fell significantly, but dopamine and homovanillic acid levels were unchanged. Plasma norepinephrine, normetanephrine, and epinephrine levels decreased 30 to 50%, and supine dopamine levels also fell. The percent fall in supine blood pressure was related to the fall of cerebrospinal fluid and plasma norepinephrine. There were also positive relationships between the decreases of plasma norepinephrine and of normetanephrine and dopamine. The cerebrospinal fluid/plasma norepinephrine ratio was unaffected by clonidine, suggesting that the drug lowered both pools equally. Our findings indicate that clonidine decreases both central and peripheral norepinephrine activity. The dopaminergic activity of cerebrospinal fluid was unaffected by clonidine, and though plasma dopamine levels tended to be lower after treatment, mean plasma prolactin level, an index of dopaminergic activity, was also unchanged. The fall in plasma epinephrine level is probably related to diminished sympathetic adrenomedullary stimulation and is unlikely to contribute to clonidine's antihypertensive action. These results also suggest that measurement of normetanephrine in cerebrospinal fluid and plasma provides a good index of norepinephrine activity.

The relationship of free and conjugated catecholamines in plasma and cerebrospinal fluid in cerebral and meningeal disease

The concentration of free and conjugated norepinephrine (NE), epinephrine (E) and dopamine (DA) were measured by a modified radio-enzymatic assay in the plasma and in the cerebrospinal fluid (CSF) of 45 patients with normal and in 21 patients with disturbed blood-CSF barriers. In patients with an undisturbed blood-CSF barrier the free NE and E in CSF were 128 +/- 45 ng/l and 27 +/- 20 ng/l (mean values +/- S.E.), respectively, and represented about 50% of the average plasma values. Mean DA was not different in plasma (47 +/- 22 ng/l) and in CSF (41 +/- 19 ng/l). Both in plasma and in CSF, considerable higher free catecholamine (CA) levels were measured in patients with dysfunction of the blood-CSF barrier. In one patient with bacterial meningitis twofold higher concentrations of free NE and DA in CSF as compared with plasma were detectable. Sulfate conjugates of catecholamines are predominant in plasma and CSF. The contribution of conjugated CA to total CA in plasma from patients with normal blood-CSF barrier averaged 69.7%, 63.1% and 98.1% for NE, E and DA, respectively and was significantly lower in the CSF (p less than 0.001). In patients with disturbed blood-CSF barrier, the increases of conjugated CA were more pronounced in CSF than in plasma. Further, the contribution of conjugated NE and E to total NE and E in CSF was not only increased in patients with bacterial meningitis, but also in patients with renal insufficiency compared to the "control" patients (p less than 0.02 and p less than 0.001 resp.). Free and conjugated NE, E and DA in the plasma and CSF were related significantly (p less than 0.01 resp.) with stronger correlation for conjugated CA (p less than 0.001 resp.). These results together with findings in the literature, suggest that there is little or no rostral-caudal gradient in CSF CA conjugate concentrations and that even in patients with intact blood-CSF barrier plasma conjugated CA concentrations influence those in CSF. Thus only free CA levels in CSF may reflect the central adrenergic activity.

Free and conjugated amines in human lumbar cerebrospinal fluid

Significant amounts of acid-hydrolyzable conjugates of 3,4-dihydroxyphenylethylamine, norepinephrine, and 5-hydroxytryptamine were detected in lumbar CSF from 22 awake unpremedicated healthy individuals. In the CSF samples, the amounts of conjugated amines almost always exceeded the amounts of free amines, but were less than the amounts of the acid metabolites 3,4-dihydroxyphenylacetic acid, homovanillic acid, and 5-hydroxyindoleacetic acid.

Effects of alcohol on cerebrospinal fluid norepinephrine in rhesus monkeys

Alcohol (1-3 g/kg) significantly increased the concentration of cerebrospinal fluid (CSF) norepinephrine (NE) in rhesus monkeys. This effect is consistent with the previously demonstrated activational and possible antidepressant effect of low doses of alcohol. The greatest increase was observed in subjects with low baseline levels of CSF NE. Individual differences in activation or euphoria could be related to differential increases in CSF NE following alcohol consumption.

Clonidine reduces elevated cerebrospinal fluid catecholamine levels in patients with essential hypertension

Cerebrospinal fluid (CSF) catecholamines were measured in normotensive patients and in patients with mild to moderate essential hypertension. CSF-norepinephrine (NE) concentrations were 50% lower in the normotensive individuals (127 +/- 28 vs. 240 +/- 23 pg/ml) (P less than 0.01). In hypertensive patients, CSF-NE was inversely related to age (r = -0.68; P less than 0.01) and directly related to plasma NE (r = 0.61; P less than 0.05). Clonidine (450 mcg/day for 2 weeks) significantly reduced CSF-NE (-40%) in hypertensive patients. In addition, it decreased blood pressure, plasma and urinary NE. Urinary VMA was not affected by clonidine. No correlation was observed between clonidine effects on BP and on plasma or CSF catecholamines. This study indicates that patients with essential hypertension have elevated levels of CSF-NE which are reduced after treatment with clonidine. The elevation of CSF-NE suggests that central (spinal?) noradrenergic activity may be increased in patients with mild to moderate essential hypertension, and that can be reduced by treatment with clonidine.

Cerebrospinal fluid measures of neurotransmitter changes associated with pharmacological alteration of the despair response to social separation in rhesus monkeys

Social separation is a risk factor for major depressions that can be modeled in nonhuman primates. Changes in central monoamine neurotransmission are also likely to be involved in major depression. This study examined the relationship between separation-induced depressive-like behavior and central monoamine neurotransmitter changes in rhesus monkeys. Measures of cerebrospinal fluid (CSF) norepinephrine (NE), 5-hydroxyindoleacetic acid (5HIAA), and homovanillic acid (HVA) were used to assess the neurobiological impact of social separation and drug treatments alone or in combination. alpha-Methyl-p-tyrosine exacerbated, and fusaric acid ameliorated, the depressive-like response to separation. Probenecid-induced accumulations of HVA and 5HIAA reflected changes in behavior, but were not consistently affected by drug treatment. In contrast, pretreatment CSF NE was comparatively stable across repeated sampling, and drug-induced changes in this measure were correlated with changes in behavior. Low CSF NE, whether drug-induced or naturally occurring, was associated with a more severe depressive-like response to separation.

Central nervous system catecholamine metabolism in Korsakoff's psychosis

We attempted to replicate previous reports of impaired central noradrenergic activity in patients with Korsakoff's psychosis. No differences were demonstrated in lumbar cerebrospinal fluid concentrations of norepinephrine or its major metabolite, 3-methoxy-4-hydroxyphenyl glycol (MHPG), or in the contribution of plasma to cerebrospinal fluid free MHPG in 6 patients with clinically well characterized Korsakoff's psychosis and 8 age-matched healthy, normal volunteers. Likewise, cerebrospinal fluid concentrations of the major metabolites of dopamine (homovanillic acid) and serotonin (5-hydroxyindoleacetic acid) were the same in patients and controls.

Measurement of the GH and other responses to clonidine at different times of the day in normal subjects

The growth hormone response to clonidine may be impaired in some patients with endogenous depression. To determine whether or not this change is due to a circadian variation in the GH response to clonidine, this measure has been studied in normal subjects at 0900, 1800 and 2100 hr. Similar responses were obtained at 0900 and 1800 hr. The responses at 2100 hr could not be interpreted, as the baseline plasma GH was raised. At no time of day were there impaired GH responses similar to those found in endogenous depression. The effects of clonidine upon blood pressure and alertness were similar at the three times studied, providing no support for any circadian rhythm in the function of the alpha 2-adrenoceptors that mediate these effects of clonidine.

Light and propranolol suppress the nocturnal elevation of serotonin in the cerebrospinal fluid of rhesus monkeys

Markedly elevated nighttime concentrations of serotonin in rhesus monkey cerebrospinal fluid were reduced to daytime levels by exposing the monkeys to continuous light or to the beta-adrenergic antagonist propranolol. Nighttime elevations of melatonin in cerebrospinal fluid were also suppressed by propranolol and light. Serotonin released in large quantities at night appears to be regulated like melatonin, and may act as a cerebroventricular hormone to influence brain and pituitary function at night.

Increased cerebrospinal fluid norepinephrine in essential hypertension

Studies in man and animals suggest increased central noradrenergic activity in hypertension. We can now measure norepinephrine (NE) in cerebrospinal fluid (CSF) accurately and this should provide an index of central noradrenergic activity. NE in CSF is very labile and altered by anxiety, stress, drugs, sodium balance and other factors. When these factors are controlled, NE in CSF appears elevated in essential hypertensives, particularly among young patients. Neurologic diseases that alter NE in CSF cause parallel alterations in blood pressure. Increased central noradrenergic activity is reflected in CSF NE levels and may cause some forms of hypertension.

Essential hypertension: central and peripheral norepinephrine

The concentration of norepinephrine in cerebrospinal fluid from patients with essential hypertension is higher than that from healthy normal volunteers, but the concentrations of norepinephrine in plasma from these groups are similar. This finding indicates that central nervous system noradrenergic hyperactivity occurs in essential hypertension but apparently is not reflected in abnormal function of the peripheral sympathetic nervous system in these patients.

Circadian rhythm in rat brain opiate receptor

To investigate diurnal variations in opiate receptor binding, the amount of specifically bound [3H]naloxone was measured at 4-h intervals across a 24-h period in the forebrains of rats that had been housed under a controlled light--dark cycle (lights on from 07.00 to 19.00 h) for 3 weeks. A significant rhythm with a peak at 22.00 h was found, the amplitude was 46--78%. In the absence of time cues, this circadian rhythm persisted with a peak at 02.00--06.00 h and an amplitude of 88%. Scatchard analysis indicated that the differences in binding throughout the day were due not to changes in affinity, but to changes in the number of binding sites.

Physiological factors in childhood epilepsy

The identification and correction of adverse physiological changes that lead to seizures in children can improve the effectiveness of current therapeutic practices in epilepsy. It is proposed that various circadian rhythms (respiration, hormones, water balance, electrolytes, intracranial pressure, blood pressure), meteorological phenomena (barometric presure, ambient environmental temperature, relative humidity), and developmental processes can profoundly influence the precipitation or prevention of seizures through their physiological effects.

Age effect on dopamine and serotonin metabolite levels in cerebrospinal fluid

Homovanillic acid (HVA), 5-hydroxyindoleacetic acid (5-HIAA), and 3-methoxy-4-hydroxyphenylethylene glycol (MHPG) were measured in lumbar cerebrospinal fluid from a group of patients ranging in age from 1 week to 45 years. Quantitation of these biogenic amine metabolites was achieved using a gas chromatographic/mass spectrometric technique. The subjects had various specific disorders of the nervous system, though patients with movement disorders and biochemical defects known to affect the neurotransmitter systems examined in this study were specifically avoided. The results indicated a strong inverse correlation in children between CSF HVA and 5-HIAA concentrations and age. The decline in these metabolites with age appeared to be exponential. No significant age effect was observed for MHPG. The results indicate the importance of comparing CSF metabolite levels in children with values in age-matched controls.

Schizophrenia: elevated cerebrospinal fluid norepinephrine

Concentrations of norepinephrine in cerebrospinal fluid are higher in schizophrenic patients, particularly in those with paranoid features, than in normal volunteer subjects of the same age. This observation supports recent reports of elevated concentrations of norepinephrine in specific brain areas adjacent to the cerebral ventricles of paranoid schizophrenic patients. Overflow of the amine from periventricular regions into the cerebrospinal fluid may reflect abnormally high release or diminished enzymatic destruction of norepinephrine in patients with schizophrenia.

Relationship between cerebrospinal fluid norepinephrine and blood pressure in neurologic patients

In 126 patients hospitalized for various diseases norepinephrine in cerebrospinal fluid correlated with blood pressure (r = 0.41, p < 0.0001). Plasma and cerebrospinal fluid norepinephrine levels correlated with heart rate. Central noradrenergic nerves help control blood pressure and may be involved in human hypertension.

Norepinephrine elevations in cerebrospinal fluid after d- and l-amphetamine

We continuously collected cerebrospinal fluid (CSF) from the lateral ventricles of monkeys and gave them from 0.1 to 1.0 mg/kg d- or l-amphetamine intravenously. The norepinephrine (NE) content of their CSF had a small circadian rhythm and a large increase after amphetamine. 1.0 mg/kg amphetamine gave a four-fold rise in CSF-NE which remained elevated for 33 h, smaller doses gave proportionately lesser responses. Both d- and l-amphetamine caused similar NE elevations except for minor differences at the highest dose. If there are differences in behavioral effects of moderate doses of d- and l-amphetamine, they are probably not due to a general difference in central NE release from these stereoisomers.

Raised cerebrospinal fluid norepinephrine in some patients with primary hypertension

To test whether central neurogenic factors participate in blood pressure elevation in primary hypertension, we studied the concentrations of: norepinephrine, epinephrine and dopamine-beta-hydroxylase (DBH) in cerebrospinal fluid (CSF); and norepinephrine, epinephrine, DBH and plasma renin activity (PRA) in plasma of 22 subjects (seven with primary hypertension, 11 normotensive patients with non-systemic neurological disorders, and four with secondary hypertension). Plasma and CSF norepinephrine (NE) were increased in primary hypertensives compared to normotensives. Cerebrospinal fluid norepinephrine was related to diastolic blood pressure, and systolic blood pressure when normotensive and primary hypertensives were taken together. The CSF norepinephrine of primary hypertensive patients was correlated with natural log PRA. The CSF norepinephrine was correlated inversely with age in primary hypertensive patients but not in the normotensive subjects. The low CSF norepinephrine and epinephrine, despite markedly increased plasma NE and epinephrine, in two patients with pheochromocytoma, indicate a blood-brain barrier for these neurohormones. The observations support the view that the central sympathetic nervous system is involved in the pathogenesis of primary hypertension, particularly in younger patients.

Circadian variation of blood-pressure

Continuous intra-arterial blood-pressure and electrocardiogram recordings were obtained in twenty hypertensive and five normotensive ambulant patients. Blood-pressure was highest mid-morning and then fell progressively throughout the remainder of the day. Blood-pressure was lowest at 3 A.M. and began to rise again during the early hours of the morning before waking. These findings may have important consequences with regard to the therapeutic management of hypertension.

Hyperalgesia induced by naloxone follows diurnal rhythm in responsivity to painful stimuli

A diurnal rhythm was observed in the responsiveness of mice to nociceptive stimuli and in the hyperalgesic activity of endogenous opioid peptides and may partly account for previous controversy over the direct action of naloxone in opiate-naive animals.

Effect of chlorpromazine treatment on monoamine metabolite levels in cerebrospinal fluid of psychotic patients

Levels of HVA, MOPEG and 5-HIAA in cerebrospinal fluid (CSF) from psychotic men and women with a schizophrenic symptomatology were measured by mass fragmentography. Measurements were made before, 2 and 4 weeks after treatment with chlorpromazine (CPZ) which was given randomly in doses of 200, 400 or 600 mg per day. Before treatment there were positive correlations between the levels of HVA and 5-HIAA in both sexes. During CPZ treatment HVA was significantly elevated, whereas MOPEG and 5-HIAA were reduced. There was a tendency towards tolerance to CPZ's effect on HVA during treatment but a significant effect persisted after 4 weeks. No indication of tolerance to the effects on MOPEG or 5-hiaa was found. There were the same tendencies for the elevations of the HVA/MOPEG and HVA/5-HIAA ratios. The changes in HVA, MOPEG, 5-HIAA, HVA/MOPEG and HVA/5-HIAA were related to dose of CPZ in men but not in women. The bidirectional change of the different metabolites in CSF during CPZ treatment excluses a general and non-specific mechanism for the metabolite changes. The HVA elevation is in accordance with previous results in animals and man, and is presumably related to blockade of central dopamine receptors. Possible mechanisms for the effects on MOPEG and 5-HIAA are discussed.