Sensory circumventricular organs: central roles in integrated autonomic regulation

Circumventricular organs (CVO) play a critical role as transducers of information between the blood, neurons and the cerebral spinal fluid (CSF). They permit both the release and sensing of hormones without disrupting the blood-brain barrier (BBB) and as a consequence of such abilities the CVOs are now well established to have essential regulatory actions in diverse physiological functions. The sensory CVOs are essential signal transducers located at the blood-brain interface regulating autonomic function. They have a proven role in the control of cardiovascular function and body fluid regulation, and have significant involvement in central immune response, feeding behavior and reproduction, the extent of which is still to be determined. This review will attempt to summarize the research on these topics to date. The complexities associated with sensory CVO exploration are intense, but should continue to result in valuable contributions to our understanding of brain function.

Neuroendocrinology of cerebrospinal fluid: peptides, steroids, and other hormones

Cerebrospinal fluid (CSF) has been implicated as a conduit in neuroendocrine integration. Evidence suggests that the ventricular CSF may promote the central distribution, enable the dilutional inactivation (sink effect), and facilitate the peripheral delivery of neurally secreted hormones. This discussion of the sites of origin and concentration gradients of CSF hormones and of both physiological and pharmacological variations in the hormonal content of the CSF provides insight into the putative role of CSF in neuroendocrine regulation. Normal or control concentrations of peptides, steroids, and other hormones present in human lumbar CSF are listed to provide a physiological base line to which the CSF hormonal profile of patients may be compared. The individual, somatotopic, chronological, endocrinological, pharmacological, and possible artifactual variations in CSF hormonal composition are presented to facilitate the formulation of clinical protocols and to eliminate possible sources of error.

Neurochemical effects of vagus nerve stimulation in humans

An implanted stimulating device chronically stimulated the left cervical vagus nerve in epileptic patients. Cerebrospinal fluid concentrations of free and total gamma-aminobutyric acid, homovanillic acid, 5-hydroxyindoleacetic acid, aspartate, glutamate, asparagine, serine, glutamine, glycine, phosphoethanolamine, taurine, alanine, tyrosine, ethanolamine, valine, phenylalanine, isoleucine, vasoactive intestinal peptide, beta-endorphin, and somatostatin were measured before and after 2 months of chronic stimulation in six patients. Significant increases were seen in homovanillic acid and 5-hydroxyindoleacetic acid in three patients, and significant decreases in aspartate were seen in five patients. These changes were associated with a decrease in seizure frequency.

Steroid hormones and steroid hormone binding globulins in cerebrospinal fluid studied in individuals with intact and with disturbed blood-cerebrospinal fluid barrier

We measured in simultaneously withdrawn cerebrospinal fluid (CSF) and serum samples from 56 endocrinologically grossly normal patients the concentrations of several lipophilic unconjugated steroids [i.e. dehydroepiandrosterone (DHEA), androstenedione, cortisol, progesterone, testosterone] and their hydrophilic counterparts, i.e. DHEA-sulfate, or hydrophilic binding proteins, i.e. albumin, sex hormone-binding globulin (SHBG) and corticosterone-binding globulin (CBG). CSF levels of total (i.e. free plus protein-bound) DHEA, androstenedione, cortisol, progesterone, and testosterone were found to be in the 0.02-2 nM range and only cortisol reached levels approximately 20 nM. These values were of the same order of magnitude as the reported and calculated free serum levels of these steroids. In patients with disturbed (abnormally leaky) blood-CSF barrier (BCB) function, CSF levels of these steroids were not different from those with intact BCB, in contrast to DHEA-sulfate, CBG and SHBG whose CSF levels were significantly elevated, that is similar (i.e. 2-5) fold as those of albumin. In vitro demonstrated low affinity (micromolar) interactions of steroids with neuronal membrane-bound neurotransmitter receptors should be considered in perspective to the here reported finding that steroids occur in vivo at best in nanomolar concentrations in the CSF. Whether in other extracellular fluid compartments of the brain higher levels of steroids than in CSF can accumulate is as yet not clear. Very probably, pathological production or excessive dosage of steroids that are negligibly bound to SHBG or CBG will produce CSF and brain levels in the near micromolar range.

Stress hormones in blood and cerebrospinal fluid of conscious sheep: effect of hemorrhage

Acute moderate hemorrhage (15 ml/kg withdrawn over 10 min) was used to study stress hormone changes in blood and cerebrospinal fluid (CSF) of conscious sheep with chronic indwelling intracerebroventricular catheters. Mean plasma arginine vasopressin (AVP) and ACTH rose 150- and 14-fold, respectively, above basal values to peak levels at 20 min after onset of hemorrhage. A smaller (4- to 5-fold) rise occurred in plasma angiotensin II (AII) to peak levels at 10 min. The corticosteroid response (cortisol and aldosterone) occurred later (peak at 45 min) and was consistent with the dependence of these steroids on plasma ACTH and AII changes. Increases in plasma epinephrine and norepinephrine were small and transient. Compared to changes in plasma, changes in CSF hormone levels after hemorrhage were small and independent of plasma concentrations. Mean CSF AVP increased to peak levels at 15 min whereas rises in CSF ACTH, AII-like immunoreactivity, and cortisol were slower and delayed in comparison with the patterns observed in plasma. Despite evidence of increased sympathetic activity, and rise in plasma catecholamines, CSF epinephrine fell after hemorrhage and CSF norepinephrine did not change. These results show that in conscious sheep rapid and major increases in plasma AVP, ACTH, and AII follow acute moderate hemorrhage. Concomitant changes in CSF hormone levels are small and delayed. With the possible exception of AVP it appears unlikely that the acute systemic hormone response to hemorrhage is determined by hormone changes in CSF.

The CSF and arterial to internal jugular venous hormonal differences during exercise in humans

Strenuous exercise increases the cerebral uptake of carbohydrate out of proportion to that of oxygen, but it is unknown whether such enhanced carbohydrate uptake is influenced by the marked endocrine response to exercise. During exhaustive exercise this study evaluated the a-v differences across the brain (a-v diff) of hormones that could influence its carbohydrate uptake (n= 9). In addition, neuroendocrine activity and a potential uptake of hormones via the cerebrospinal fluid (CSF) were assessed by lumbar puncture postexercise and at rest (n= 6). Exercise increased the arterial concentration of noradrenaline and adrenaline, but there was no cerebral uptake. However, following exercise CSF noradrenaline was 1.4 (0.73-5.5) nmol l(-1), and higher than at rest, 0.3 (0.19-1.84) nmol l(-1) (P < 0.05), whereas adrenaline could not be detected. Exercise increased both the arterial concentration of NH(4)(+) and its a-v diff, which increased from 1 (-12 to 5) to 17 (5-41) micromol l(-1) (P < 0.05), while the CSF NH(4)(+) was reduced to 7 (0-10) versus 11 (7-16) micromol l(-1) (P < 0.05). There was no release from, or accumulation in the brain of interleukin (IL)-6, tumour necrosis factor (TNF-alpha), heatshock protein (HSP72), insulin, or insulin-like growth factor (IGF)-I. The findings indicate that for maximal exercise, the concentration of noradrenaline is increased within the brain, whereas blood borne hormones and cytokines are seemingly unimportant. The results support the notion that the exercise-induced changes in brain metabolism are controlled by factors intrinsic to the brain.

Effects of insulin-induced hypoglycemia on plasma and cerebrospinal fluid levels of ir-beta-endorphins, ACTH, cortisol, norepinephrine, insulin and glucose in the conscious dog

This study was designed to assess effects of insulin-induced hypoglycemia on plasma and cerebrospinal fluid (CSF) levels of immunoreactive (ir) beta-endorphins, adrenocorticotropin (ACTH), cortisol, norepinephrine, insulin, and glucose in the conscious, overnight fasted dog. Dogs received either an intravenous infusion of saline or insulin (5 mU/kg/min) for 3 h. Infusion of saline alone in conjunction with acute sampling of CSF caused no measurable perturbations of glucose homeostasis. Insulin infusion caused a 60% drop in both plasma and CSF glucose. Plasma levels of ir-beta-endorphins, ACTH and cortisol rose markedly. CSF levels of ir-beta-endorphins and ACTH also increased. While the magnitude of the increase was smaller than that in the plasma, it was greater than would be expected if crossover of the peptides from the plasma were the sole source of the increase. Hypoglycemia also induced elevations in CSF cortisol and insulin. In addition, there was a 45% decrease in CSF norepinephrine in spite of large elevations of norepinephrine in the plasma. We conclude that hypoglycemia is associated with marked changes in central as well as peripheral levels of neuroendocrine factors. The importance of these changes in mediating acute and long-term responses to hypoglycemia remains to be established.

Physiological and therapeutic effects of high frequency electrical pulses

The results of stimulating human subjects with the LISS Cranial Stimulator (LCS) and the LISS Body Stimulator (LBS) include an increase or decrease in the activities of certain neurotransmitters and neurohormones and the reduction of associated pain, insomnia, depression, and spasticity. The effects were documented in human subjects with measurements of the serum concentration of the various agents and assessments of the symptoms being performed before and after stimulation. The stimulators had a carrier frequency of 15,000 hz, which utilizes the bulk capacitance of the body, and a 15 hz modulating bioactive frequency. The second modulating frequency presently used, 500 hz, reduces the energy input to the patient by half. Significant increases in levels of CSF serotonin and beta endorphin were recorded post stimulation. There were also elevations in the levels of plasma serotonin, beta endorphin, GABA and DHEA together with diminished levels of cortisol and tryptophan. Concomitant with these changes were significant improvements in the symptoms of pain, insomnia, spasticity, depression, and headache.

Cerebrospinal fluid estrone in pseudotumor cerebri: a change in cerebral steroid hormone metabolism?

Estrogen and androgen hormones were studied in the plasma and cerebrospinal fluid (CSF) of five patients affected by pseudotumor cerebri (PTC). Six men and six women without cerebral or endocrine diseases were selected as controls. Androstenedione (A), testosterone (T), 17-hydroxyprogesterone (17OH-P), E1 and E2 were measured in plasma and CSF in baseline conditions and following 1 month prednisone therapy (2 mg/die, per os) using RIA following chromatographic separation on celite microcolumns. Men and women affected by PTC show increased CSF E1 levels and marked decreased CSF A levels, with respect to controls. In plasma, on the contrary, normal values of these parameters were observed in PTC. In normal subjects A/E1 ratio shows the same values in plasma and CSF, suggesting for the two hormones analogous feasibility to cross the blood brain barrier. In PTC patients A/E1 ratio is comparable to controls in plasma, but lower in CSF as a result of decreased A and increased E1 contents. The CSF imbalance between A and E1 attenuates but does not disappear after treatment. No correlation is found between pressure levels and steroid pattern both in baseline condition or after one month of treatment. In conclusion, our results demonstrate that PTC is not only associated with increased CSF E1 levels, as previously suggested, but, above all, with decreased CSF A levels and this hormonal impairement seems to be confined to the CSF compartment and not observed in plasma. These data do not lead to any definitive conclusion about the role of altered CSF estrogen and androgen levels in PTC pathogenesis.(ABSTRACT TRUNCATED AT 250 WORDS)

Changes with aging of steroidal levels in the cerebrospinal fluid of women

OBJECTIVE

Age-related changes of steroid levels in the central nervous system (CNS) are not well understood. To investigate whether steroidal conditions in the CNS of women change with aging and menopause, steroid levels have been measured in serum and cerebrospinal fluid (CSF), and examined correlations with aging.

METHODS

Serum and CSF concentrations of estradiol (E2), cortisol, dehydroepiandrosterone (DHEA), DHEA sulfate (DHEAS) and albumin were measured in 80 female patients who underwent operations for benign gynecological diseases. They had no endocrinological or neurological disorders and were aged 17-71 years; 62 patients were in premenopause and 18 were in postmenopause.

RESULTS

Serum levels of E2 decreased markedly after menopause, while levels of DHEA and DHEAS decreased gradually with age. There was no significant change with age of serum cortisol levels. The CSF concentrations of E2 (0.2-3 pg/ml) decreased with age [correlation coefficient (r)= 0.31, P < 0.01]. The CSF DHEA levels (0.1-0.8 ng/ml) did not change with age although not significantly, but CSF cortisol levels (0.1-0.6 microg/dl) increased with age (r = 0.35, P < 0.01). The CSF DHEAS concentrations were below the sensitivity of the radioimmunoassay (RIA) (1 ng/ml). The CSF/serum ratios of cortisol increased with age (r = 0.30, P < 0.01), as did those of DHEA (r = 0.55, P < 0.01). Although serum albumin levels did not change throughout life, CSF albumin levels and CSF/serum albumin ratios increased gradually with age (r = 0.28, P = 0.052; r = 0.23, P = 0.114, respectively), but there was no significance. There were marked decreases of serum E2 and DHEA levels and CSF E2 levels in postmenopausal women (P < 0.05), but CSF cortisol levels increased (P < 0.05) and DHEA levels in CSF were maintained after menopause.

CONCLUSION

These results indicate that steroids in CSF become cortisol dominated and deficient in estrogens with aging, especially after menopause.

Hormonal changes in cerebral infarction in the young and elderly

Fifty-one patients with CCT verified cerebral infarction were submitted to serum and CSF radioimmunoassay of FSH, LH, estradiol (E2), progesterone, testosterone, cortisol and T4. The results were compared to those of 82 matched controls. Our findings suggest that (1) high serum E2 is a risk factor of stroke in males; (2) low serum T4 is a risk factor in males; (3) serum testosterone is reduced in acute stroke in males confirming that it is stress sensitive; (4) serum LH was higher in hypertensive thrombotic males when compared to normotensive ones, and (5) FSH, LH, E2 and T4 are undetectable in CSF of patients and controls.

Physiological neuroendocrinology of peptides, steroids and other hormones in cerebrospinal fluid

Cerebrospinal fluid acts as a conduit in neuroendocrine regulation. Valid assessment of normal cerebrospinal fluid levels of peptides, steroids and other hormones requires clarification of reference concentrations in control patients and normal volunteers. Awareness of factors which may alter neuronal activity and, in turn, the relative composition of cerebrospinal fluid constituents is essential to the accurate sampling and hormonal analysis of cerebrospinal fluid.

Cerebrospinal Profiling of Proteins, Lipids, Small Molecules, and Elements: Application to the Study of Migraine Pathophysiology

BACKGROUND AND OBJECTIVES

The fundamental reason that the migraine phenotype is experienced by sufferers and not by the more fortunate populace is not known. We believe a common biochemical pathway is involved, and are attempting to reveal this by using an objective and broad survey of molecular composition, rather than the conventional hypothesis-driven approaches that are narrowly focused and subjective.

METHODS

This article discusses the application of CSF bioanalysis in a clinical sample and summarizes preliminary findings, which are described more fully in papers currently in press.

RESULTS

In migraineurs during a migraine attack, compared with a migraine-free period, changes have been documented in the concentrations of specific proteins, lipids, small molecules, and elements in the CSF The degree to which these changes are specific to migraine remains to be determined.

CONCLUSIONS

As the CSF profiles for proteins, lipids, small molecules, and elements become better delineated in both healthy individuals and in disease states such as migraine, measurement of changes in CSF composition will provide the potential for improving diagnosis, correlating molecular events with symptoms, developing new therapeutic strategies, and enhancing the ability to monitor the results of therapy.

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.

CSF and endocrine studies of premenstrual syndrome

Eight women with prospectively documented premenstrual syndrome (PMS) underwent multiple samplings for estradiol, progesterone, prolactin, cortisol, and plasma 3-methoxy-4-hydroxyphenylglycol (MHPG) during an asymptomatic midcycle (late follicular) and a symptomatic premenstrual (late luteal) phase of the menstrual cycle. Cerebrospinal fluid (CSF) was collected for analysis of MHPG, norepinephrine (NE), 5-hydroxyindoleacetic acid (5-HIAA), dihydroxyphenylacetic acid (DOPAC), gamma-aminobutyric acid (GABA), homovanillic acid (HVA), tyrosine, tryptophan, beta-endorphin, prostaglandins, adrenocorticotropic hormone (ACTH), and arginine vasopressin (AVP). In subsequent months, a dexamethasone suppression test (DST) and a thyrotropin-releasing hormone (TRH) stimulation test were performed during midcycle and premenstrual phases. Significant results included increased CSF concentrations of MHPG in the premenstrual, as compared with the midcycle, phase of the cycle, and increased plasma cortisol concentrations during the midcycle phase. The DST showed a 62% overall rate of nonsuppression, irrespective of menstrual cycle phase. Though there were no abnormalities of thyrotropin-stimulating hormone (TSH) after TRH stimulation, the mean delta maximum prolactin values after TRH stimulation were higher than reported normal values both at midcycle and premenstrually. These pilot data suggest hormonal axes that might be worthy of further systematic investigation in future studies of PMS.

Hormone pathways in cerebrospinal fluid

At present, it is difficult to reconcile the relative absence of clear, positive evidence for hormone pathways of the CSF and the ventricular route hypothesis, even when only very particular hormone systems (such as the LHRH system) are examined. One must consider several of the parameters described previously, such as possible entry of hormones into the CSF via the choroid plexus, CVOs and intraventricular nerve endings, or even the possibility that they may cross the blood-brain barrier. Of course, these considerations are important for whatever hormone system is being studied, and there probably may turn out to be several pathways for any particular hormone to access the CSF. In conclusion, despite the fact that there are many acceptable features of the ventricular route hypothesis, more investigation remains to be undertaken in order to fully appreciate the importance of the CSF as an integrator of neuronal and endocrine function.