Cerebrospinal Fluid Corticotropin-releasing Hormone Research Articles

Early life adversity in primates: Behavioral, endocrine, and neural effects

BackgroundEvidence suggests that early life adversity is associated with maladaptive behaviors and is commonly an antecedent of stress-related psychopathology. This is particularly relevant to rearing in primate species as infant primates depend on prolonged, nurturant rearing by caregivers for normal development. To further understand the consequences of early life rearing adversity, and the relation among alterations in behavior, physiology and brain function, we assessed young monkeys that had experienced maternal separation followed by peer rearing with behavioral, endocrine and multimodal neuroimaging measures. Methods50 young rhesus monkeys were studied, half of which were rejected by their mothers and peer reared, and the other half were reared by their mothers. Assessments were performed at approximately 1.8 years of age and included: threat related behavioral and cortisol responses, cerebrospinal fluid (CSF) measurements of oxytocin and corticotropin releasing hormone (CRH), and multimodal neuroimaging measures (anatomical scans, resting functional connectivity, diffusion tensor imaging, and threat-related regional glucose metabolism). ResultsThe results demonstrated alterations across behavioral, endocrine, and neuroimaging measures in young monkeys that were reared without their mothers. At a behavioral level in response to a potential threat, peer reared animals engaged in significantly less freezing behavior (p = 0.022) along with increased self-directed behaviors (p < 0.012). Levels of oxytocin in the CSF, but not plasma, were significantly reduced in the peer reared animals (p = 0.019). No differences in plasma cortisol or CSF CRH were observed. Diffusion tensor imaging revealed significantly decreased white matter density across the brain. Exploratory correlational and permutation analyses suggest that the impact of peer rearing on behavior, endocrine and brain structural alterations are mediated by separate parallel mechanisms. ConclusionsTaken together, these results demonstrate in NHPs the importance of maternal rearing on the development of brain, behavior and hormonal systems that are linked to social functioning and adaptive responses. The findings suggest that the effects of maternal deprivation are mediated via multiple independent pathways which may account for the heterogeneity in behavioral and biological alterations observed in individuals that have experienced this early life adversity.

Lower cerebrospinal fluid CRH concentration in chronic schizophrenia with negative symptoms

Some patients with schizophrenia have impaired hypothalamic-pituitary-adrenal axis function. However, there is a dearth of studies focusing on corticotropin-releasing hormone (CRH) levels in the brains of schizophrenia patients, which motivated us to examine whether cerebrospinal fluid (CSF) CRH concentrations are altered in these patients. We also examined the possible correlation of CSF CRH level with clinical variables such as schizophrenia symptoms and antipsychotic medication. The study population comprised 20 patients with a diagnosis of schizophrenia according to DSM-5 criteria and 25 healthy controls, who underwent lumbar puncture. Most of the patients were treated with antipsychotic drugs and their doses were converted to chlorpromazine (CP) equivalent values. CSF CRH concentrations were measured by an enzyme immunoassay. Symptom severity was assessed using the Positive and Negative Syndrome Scale (PANSS). There was a significantly lower CSF CRH concentration in the patients than in the controls (Mann-Whitney U test: p = 0.014). A significantly negative correlation of CSF CRH levels with PANSS negative scores was found in the patients (Spearman's: ρ = −0.58, p = 0.007). However, CSF CRH concentrations were not significantly correlated with the PANSS total (ρ = −0.035, p = 0.89), positive (ρ = 0.25, p = 0.30), or general psychopathology (ρ = 0.13, p = 0.59) scores. No significant correlation was found with CP equivalent values (ρ = 0.00, p = 1.00). In conclusion, we found that the patients with schizophrenia had lower CSF CRH concentrations compared to the controls and that the lower CSF CRH was associated with negative symptoms of the illness. Further studies in a larger sample and in drug-free patients are warranted.

Temporal changes in the cerebrospinal fluid allopregnanolone concentration and hypothalamic-pituitary-adrenal axis activity in sheep during pregnancy and early lactation

Research on pregnant mice and rats indicated that a neurosteroid allopregnanolone (AP) might have a stress-protective effect, decreasing the activity of the hypothalamic-pituitary-adrenal (HPA) axis. Using a sheep model in the present research, we tested a hypothesis that the cerebrospinal fluid (CSF) AP concentration changes during pregnancy and early lactation, keeping in check the secretory activity of the HPA axis. Four-hour-long CSF collections (20 μL/min, from 10:00 to 14:00) from the third brain ventricle were conducted in 8 sheep, every 4 weeks, starting from the 28th day of pregnancy until the 28th day after delivery, to determine AP and corticotropin-releasing hormone (CRH) concentrations. A maximum of 8 samples (every 30 min) were gathered from individual sheep. Each series of CSF collections was accompanied by blood sampling every 10 min, to examine the distribution of mean plasma adrenocorticotropin (ACTH) and cortisol concentrations. Six luteal-phase sheep were used as a control during the period corresponding to the first month of pregnancy. The highest AP concentration was noted in the 5th month of pregnancy compared to these in the 1st and 2nd months (P < 0.01–P < 0.001). A decrease in the CSF AP level occurred in the 1st month of lactation compared to the concentration noted before delivery (P < 0.05). The CSF CRH concentration reached the highest level in the 4th month of pregnancy compared to these in the 1st and 2nd months (P < 0.001). A decrease in the CRH concentration was observed in the 5th month (P < 0.001, vs 4th month) and then in the 1st month of lactation (P < 0.01–P < 0.001, vs other months of pregnancy). A correlation between the CSF AP and CRH concentrations during four months of pregnancy indicated a very strong relationship (r = =0.9946), but it weakened in the 5th month (r = =0.7079). Both plasma ACTH and cortisol concentrations increased from the 1st to the 4th month of pregnancy (P < 0.01–P < 0.001) and then decreased in the 5th month (P < 0.001). The concentrations of these two hormones remained at lowered levels during early lactation. The CSF CRH, as well as plasma ACTH and cortisol levels in control non-pregnant sheep were generally lower (P < 0.001) than the ones noted in mid-pregnancy. In conclusion, the increasing secretory activity of the HPA axis in pregnant sheep is accompanied by an increase in the CSF AP concentration. The protective effect of AP from excess glucocorticoids may be seen during late pregnancy and early lactation.

Corticotropin-releasing hormone and copeptin as acute stress markers in serial cerebrospinal fluid – first evidence for non-response during insulin hypoglycemia test

Background: During stress, arginine vasopressin (AVP) and corticotropin-releasing hormone (CRH) can act as potent hypothalamic stimulators of the hypothalamic pituitary adrenocortical (HPA) axis. Recently, plasma CT-proAVP, also termed copeptin, was found to be a stable and sensitive surrogate marker for AVP release. A valid assessment of both CRH and copeptin in cerebrospinal fluid (CSF) might directly quantify an individual’s current stress level. Here we investigated how concentrations of CRH and copeptin in CSF alter during insulin-induced hypoglycemia test (IHT) - which has been shown to activate both hypothalamic AVP and CRH - and hypothesized an increase of both.Methods: Five healthy young men were studied from 08:00 until 14:00 after over-night fasting. They received an i.v. injection of human insulin (0.1 IE/kg body weight) at 11:02. CSF samples were drawn from a subarachnoidal catheter every 20 minutes from 10:40 to 14:00 for the measurement of CSF CRH and CSF copeptin. Plasma adrenocorticotropic hormone (ACTH) and cortisol were analyzed in parallel.Results: Data could be assessed in three of five subjects, of which two responded to IHT by showing glucose levels of < 40 mg/dl and clinical symptoms (sweating). Despite a 17-fold, respectively 11-fold increase of plasma ACTH, neither our hypothesized increase of CSF CRH nor of CSF copeptin was seen in these two responders.Conclusions: This is the first study investigating CSF CRH and CSF copeptin in man during acute stress. Copeptin had not been measured in CSF before. Our results support recent speculations that CSF CRH is not a measure of hypothalamic but rather extrahypothalamic CRH (non-HPA CRH). Further research on copeptin in CSF is needed.

No acute suppression of cerebrospinal fluid corticotropin-releasing hormone in man by cortisol administration

Corticotropin-releasing hormone (CRH) in cerebrospinal fluid (CSF) is regarded as index of brain endocrine and behavioral functioning. We investigated the acute effects of intravenous cortisol (100mg) vs. placebo on serial CSF CRH in ten healthy men. CSF CRH concentrations were not significantly suppressed by cortisol within 3h. The origin and regulation of CSF CRH need further research.

Quetiapine affects neuropeptide Y and corticotropin-releasing hormone in cerebrospinal fluid from schizophrenia patients: relationship to depression and anxiety symptoms and to treatment response

Cumulative evidence indicates that neuropeptides play a role in the pathophysiology of schizophrenia. Early data showed increased neuropeptide Y (NPY) in cerebrospinal fluid (CSF) from schizophrenia patients and data from rodents show that antipsychotic drugs modulate NPY levels in and release from selected rat brain regions. In view of these findings we investigated whether the atypical antipsychotic quetiapine, originally used as an antipsychotic but subsequently shown to be efficient also in major depressive disorder and in both poles of bipolar disorder, would affect NPY-like immunoreactivity (-LI), and corticotropin-releasing hormone (CRH)-LI levels in CSF of schizophrenia patients. NPY-LI and CRH-LI in CSF were determined in 22 patients with schizophrenia. Lumbar puncture was performed at baseline and again after 4 wk of quetiapine treatment (600 mg/d). Patients were assessed with the Positive and Negative Syndrome Scale (PANSS) at baseline and at weekly intervals. Quetiapine treatment was associated with a significant increase in NPY-LI (p<0.001) and decrease in CRH-LI (p<0.01). Stepwise multiple regression analysis revealed that ΔNPY-LI and ΔCRH-LI levels predicted 63% (p<0.001) of the variability of the ΔPANSS total score, ΔNPY-LI 42% (p<0.05) of the ΔPANSS anxiety items (G2) and ΔCRH-LI 40% (p=0.05) of the ΔPANSS depression items (G6). These results suggest that while quetiapine's effects on monoamines are probably related to its antipsychotic properties, the modulation of NPY and CRH accounts for its antidepressant and anxiolytic effects and can be markers of response.

The effect of treatment with ketoconazole on central CRH systems of depressed patients

Steroid-synthesis inhibitors are reported to reduce psychopathology in treatment-resistant depressed patients. We studied the effect of a 3-week treatment with ketoconazole on the evening plasma concentrations of cortisol, corticosteroid-binding globulin (CBG), dehydroepiandrosterone-sulfate (DHEA-S) and adrenocorticotrope hormone (ACTH) as well as morning cerebrospinal fluid (CSF) concentrations of cortisol, corticotropin-releasing hormone (CRH) and arginine-vasopressin (AVP) in six elderly treatment-resistant depressed patients. While we found plasma cortisol concentrations to be unchanged, a decline in plasma DHEA-S concentrations indicated effective steroid-synthesis inhibition. In morning CSF we found CRH concentrations that did not change. Our preliminary observations indicate that the treatment of depressed patients with the steroid-synthesis inhibitor ketoconazole does not lead to a major increase in CSF CRH secretion.

Effects of trauma-related audiovisual stimulation on cerebrospinal fluid norepinephrine and corticotropin-releasing hormone concentrations in post-traumatic stress disorder

Although elevated concentrations of both corticotropin-releasing hormone (CRH) and norepinephrine are present in the cerebrospinal fluid (CSF) of patients with post-traumatic stress disorder (PTSD), the effects of exposure to traumatic stimuli on these stress-related hormones in CSF are unknown. A randomized, within-subject, controlled, cross-over design was used, in which patients with war-related PTSD underwent 6-h continuous lumbar CSF withdrawal on two occasions per patient (6-9 weeks apart). During one session the patients watched a 1-h film containing combat footage (traumatic film) and in the other a 1-h film on how to oil paint (neutral film). At 10-min intervals, we quantified CRH and norepinephrine in CSF, and ACTH and cortisol in plasma, before, during, and after symptom provocation. Subjective anxiety and mood were monitored using 100-mm visual analog scales. Blood pressure and heart rate were obtained every 10min from a left leg monitor. Eight of 10 patients completed two CSF withdrawal procedures each. A major drop in mood and increases in anxiety and blood pressure occurred during the traumatic relative to the neutral videotape. CSF norepinephrine rose during the traumatic film relative to the neutral videotape; this rise directly correlated with magnitude of mood drop. In contrast, CSF CRH concentrations declined during the trauma-related audiovisual stimulus, both absolutely and relative to the neutral stimulus; the magnitude of CRH decline correlated with degree of subjective worsening of anxiety level and mood. Plasma cortisol concentrations were lower and ACTH levels similar during the stress compared with the neutral videotape. CSF concentrations of the stress hormones norepinephrine and CRH differentially change after exposure to 1h of trauma-related audiovisual stimulation in chronic, combat-related PTSD. While the CSF norepinephrine increase was postulated, the decline in CSF CRH levels is surprising and could be due to audiovisual stress-induced increased uptake of CSF CRH into brain tissue, increased CRH utilization, increased CRH degradation, or to an acute stress-related inhibition or suppression of CRH secretion.

The stress system in the human brain in depression and neurodegeneration

The stress system in the human brain in depression and neurodegeneration

Higher Levels of Basal Serial CSF Cortisol in Combat Veterans With Posttraumatic Stress Disorder

Results of basal peripheral cortisol measures in posttraumatic stress disorder (PTSD) have been variable. The authors' goal was to measure CSF cortisol concentrations, which more accurately reflect brain glucocorticoid exposure, in subjects with or without PTSD. CSF was withdrawn from a subarachnoid catheter and plasma from a venous catheter, both indwelling, over a 6-hour interval to determine hourly plasma ACTH and cortisol concentrations and hourly CSF cortisol levels in eight well-characterized combat veterans with PTSD and eight matched healthy volunteers. Mean CSF cortisol concentrations were significantly higher in the subjects with PTSD (3.18 ng/ml, SD=0.33) than in the normal volunteers (2.33 ng/ml, SD=0.50), largely due to higher CSF cortisol concentration nadirs. No group differences were observed in either plasma ACTH or peripheral (plasma or urinary free) cortisol. CSF corticotropin-releasing hormone and CSF cortisol concentrations were positively and significantly correlated. Despite normal peripheral cortisol indexes in the veterans with PTSD, their CNS exposure to cortisol was greater than that of normal comparison subjects.

CSF hypocretin-1 levels in schizophrenics and controls: relationship to sleep architecture

Hypocretins/orexins are newly identified peptides of hypothalamic origin. Hypocretin deficiency is involved in the sleep disorder narcolepsy, suggesting the importance of hypocretin neurotransmission for the regulation of sleep. Hypocretin is known to excite midbrain dopaminergic neurons and to induce hyperactivity and stereotypy in animals. Altered hypocretin neurotransmission might therefore be involved in schizophrenia, since an involvement of dopaminergic mechanisms and an association with sleep disturbance are well demonstrated in patients with schizophrenia. Hypocretin is also known to affect the hypothalamic–pituitary–adrenal axis by stimulating the release of corticotropin releasing hormone (CRH). In the current study, we measured CSF hypocretin levels in 12 controls and 13 patients with chronic schizophrenia associated with moderate sleep disturbance, such as longer sleep onset latency, decreased total sleep time and decreased sleep efficacy. No difference in CSF hypocretin levels between schizophrenia and control subjects was found. CSF hypocretin levels were positively correlated with CSF CRH levels in the patient, control and combined subject populations, but the correlation did not reach statistical significance in any population. The hypocretin levels in schizophrenic patients were, however, positively and significantly correlated with sleep latency, one of the most consistent sleep abnormalities seen in schizophrenia. This correlation was not significant in controls, and no other significant correlation between CSF hypocretin levels and any measure of sleep architecture in either patients or controls was observed. Further studies of whether CNS hypocretin neurotransmission is involved in sleep and neuroendocrine abnormalities seen in patients with schizophrenia and other psychiatric conditions are warranted.

The effect of feeding on cerebrospinal fluid corticotropin-releasing hormone levels in humans

Corticotropin-releasing hormone (CRH) is a neuropeptide thought to play a role in appetite regulation. In this report, we used a serial cerebrospinal fluid (CSF) sampling technique to examine the relationship between CSF CRH, plasma ACTH and cortisol and perceptions of hunger and satiety in fasting and sated volunteers. CSF was withdrawn continuously from 11:00 AM to 5:00 PM via an indwelling subarachnoid catheter. Blood was withdrawn every 10 min via an antecubital vein catheter. Fed subjects received a meal at 1:00 PM. Subjects who were fed had lower post-prandial ratings on hunger scales and higher ratings on satiety scales. Fed subjects also had slightly lower levels of CSF CRH after feeding. Furthermore, fed subjects had higher ACTH and cortisol concentrations in the first 3 h; by the fourth h the opposite was true. Our findings do not support the hypothesis that CNS CRH is a central satiety factor in the human. Instead our findings of slightly diminished CSF CRH levels after feeding may be accounted for by the rises in glucocorticoids and their associated negative feedback effects on CNS CRH. Alternatively, our findings could also reflect changes in CRH levels associated with feeding in multiple brain areas and in the spinal cord with the net effect being in the negative direction.

Corticotropin-releasing hormone in depression and post-traumatic stress disorder

Corticotropin-releasing hormone (CRH) has been implicated in the regulation of a wide range of behaviors including arousal, motor function, feeding, and reproduction. Because depressed patients are often hypercortisolemic and intracerebroventricular administration of CRH to experimental animals produces a syndrome reminiscent of depression, dysregulation of this compound has been suggested to be involved in the pathogenesis of depressive and anxiety disorders. Studies of cerebrospinal fluid CRH levels and clinical neuroendocrine tests in patients with anxiety and affective disorders have supported this hypothesis. This review discusses these neuroendocrine findings in melancholic and atypical depression as well as post-traumatic stress disorder (PTSD). Overall, the data suggest that melancholic depression is characterized by hyperactive central CRH systems with overactivity of the pituitary-adrenal (HPA) axis. On the other hand, atypical depression is characterized by hypoactive central CRH systems and accompanying underactivity of the hypothalamic-pituitary-adrenal axis. Furthermore, the neuroendocrinology of PTSD appears to be unique, in that patients have hyperactive central CRH systems with underactivity of the pituitary-adrenal axis.

Cerebrospinal Fluid Corticotropin-Releasing Hormone in Healthy Humans: Effects of Yohimbine and Naloxone

CRH neurons projecting from the paraventricular nucleus (PVN) of the hypothalamus to the median eminence control hypothalamic-pituitary-adrenal (HPA) axis activity. However, CRH neurons outside the PVN as well as PVN neurons projecting to sites other than the median eminence also contribute to the stress response and may play a role in mood and anxiety disorders. We have attempted to investigate possible noradrenergic and opioid regulation of these non-HPA CRH neurons. We hypothesized that yohimbine (anα 2-adrenergic antagonist) would have stimulatory action on non-HPA CRH neurons, whereas naloxone (a μ-opioid receptor antagonist) would not have this effect. Adult normal volunteers received iv yohimbine (n = 5; 0.4 μg/kg), naloxone (n = 4; 125 μg/kg), or placebo (n = 3; 0.9% saline). Cerebrospinal fluid (CSF) was collected continuously, and concentrations of CSF CRH, CSF norepinephrine (NE), and plasma cortisol were measured. Administration of either yohimbine or naloxone caused significant increases in p...

Oral administration of a corticotropin-releasing hormone receptor antagonist significantly attenuates behavioral, neuroendocrine, and autonomic responses to stress in primates.

We evaluated the effects of the lipophilic nonpeptide corticotropin-releasing hormone (CRH) type 1 receptor antagonist antalarmin on the behavioral, neuroendocrine, and autonomic components of the stress response in adult male rhesus macaques. After oral administration, significant antalarmin concentrations were detected in the systemic circulation and the cerebrospinal fluid by a mass spectrometry-gas chromatography assay developed specifically for this purpose. Pharmacokinetic and dose-response studies suggested that an oral dose of 20 mg/kg was optimal for behavioral and endocrine effects. We then administered this dose in a double-blind, placebo-controlled fashion to monkeys exposed to an intense social stressor: namely, placement of two unfamiliar males in adjacent cages separated only by a transparent Plexiglas screen. Antalarmin significantly inhibited a repertoire of behaviors associated with anxiety and fear such as body tremors, grimacing, teeth gnashing, urination, and defecation. In contrast, antalarmin increased exploratory and sexual behaviors that are normally suppressed during stress. Moreover, antalarmin significantly diminished the increases in cerebrospinal fluid CRH as well as the pituitary-adrenal, sympathetic, and adrenal medullary responses to stress. We conclude that CRH plays a broad role in the physiological responses to psychological stress in primates and that a CRH type 1 receptor antagonist may be of therapeutic value in human psychiatric, reproductive, and cardiovascular disorders associated with CRH system hyperactivity.

Cerebrospinal fluid levels of corticotropin-releasing hormone in women with functional hypothalamic amenorrhea

Objective: Women with functional hypothalamic amenorrhea are anovulatory because of reduced gonadotropin-releasing hormone drive. Several studies have documented hypercortisolemia, which suggests that functional hypothalamic amenorrhea is stress-induced. Further, with recovery (resumption of ovulation), cortisol decreased and gonadotropin-releasing hormone drive increased. Corticotropin-releasing hormone can increase cortisol and decrease gonadotropin-releasing hormone. To determine its role in functional hypothalamic amenorrhea, we measured corticotropin-releasing hormone in cerebrospinal fluid along with arginine vasopressin, another potent adrenocorticotropic hormone secretagog, and β-endorphin, which is released by corticotropin-releasing hormone and can inhibit gonadotropin-releasing hormone. Study Design: Corticotropin-releasing hormone, vasopressin, and β-endorphin levels were measured in cerebrospinal fluid from 14 women with eumenorrhea and 15 women with functional hypothalamic amenorrhea. Results: Levels of corticotropin-releasing hormone in cerebrospinal fluid and of vasopressin were comparable and β-endorphin levels were lower in women with functional hypothalamic amenorrhea. Conclusions: In women with established functional hypothalamic amenorrhea, increased cortisol and reduced gonadotropin-releasing hormone are not sustained by elevated cerebrospinal-fluid corticotropin-releasing hormone, vasopressin, or β-endorphin. These data do not exclude a role for these factors in the initiation of functional hypothalamic amenorrhea. (Am J Obstet Gynecol 2000;182:776-84.)

232. Effects of acute and chronic social stress on levels of CSF corticotropin-releasing hormone

Corticotropin releasing hormone (CRH) is an evolutionary primitive neuropeptide. In addition to driving the HPA axis, brain levels of CRF mediate both behavioral and autonomic responses to stress. Dysregulation of the CRH system has been implicated in the pathophysiology of depression, anxiety, post-traumatic stress disorder, alcoholism, and drug withdrawal. Moreover, exposure to stress, early in life has been linked to adulthood psychopathology. Here, we sought to evaluate the effects of acute social stress (Experiment 1) and chronic social stress (Experiment 2) on cerebrospinal fluid levels of CRH on monkeys reared in socially normative and socially impoverished environments.

Cerebrospinal fluid corticotropin-releasing hormone levels are elevated in monkeys with patterns of brain activity associated with fearful temperament

Background: Asymmetric patterns of frontal brain activity and brain corticotropin-releasing hormone (CRH) systems have both been separately implicated in the processing of normal and abnormal emotional responses. Previous studies in rhesus monkeys demonstrated that individuals with extreme right frontal asymmetric brain electrical activity have high levels of trait-like fearful behavior and increased plasma cortisol concentrations. Methods: In this study we assessed cerebrospinal fluid (CSF) CRH concentrations in monkeys with extreme left and extreme right frontal brain electrical activity. CSF was repeatedly collected at 4, 8, 14, 40, and 52 months of age. Results: Monkeys with extreme right frontal brain activity had increased CSF CRH concentrations at all ages measured. In addition, individual differences in CSF CRH concentrations were stable from 4 to 52 months of age. Conclusions: These findings suggest that, in primates, the fearful endophenotype is characterized by increased fearful behavior, a specific pattern of frontal electrical activity, increased pituitary–adrenal activity, and increased activity of brain CRH systems. Data from other preclinical studies suggests that the increased brain CRH activity may underlie the behavioral and physiological characteristics of fearful endophenotype.

Neurobiological correlates of suicidal behavior

Studies in postmortem brain tissue from suicide victims show a presynaptic serotonergic deficit resulting in compensatory upregulation of postsynaptic 5-HT2 receptors in the prefrontal cortex. Reduced levels of cerebrospinal fluid (CSF) 5-hydroxyindoleacetic acid, the major serotonin metabolite, are associated with violent suicide attempts independent of psychiatric diagnosis and predict future suicide attempts and suicide completion, consistent with the notion of a biochemical trait. Neuroendocrine challenge tests, platelet studies and a polymorphism in the gene for tryptophan hydroxylase, the rate-limiting enzyme in the biosynthesis of serotonin, suggest that serotonergic activity may be reduced. This serotonergic abnormality might be related to the vulnerability or diathesis for suicidal behaviour by predisposing individuals to impulsive and autoaggressive behaviour. The hypothesis of hyperactivity of the hypothalamic pituitary adrenal axis (HPA) is supported by the postmortem findings of increased CSF corticotropin releasing hormone (CRH) concentrations and reduced CRH receptor binding sites in the frontal cortex of suicide victims (interpreted as downregulation following CRH hypersecretion) and dexamethasone nonsuppression in suicide attempters. Animal studies and in vitro experiments indicate that the HPA system modulates serotonergic activity. It is hypothesized that the serotonergic alterations potentially result from dysregulation of the HPA system. Data from epidemiological and clinical studies demonstrate that low levels of cholesterol are associated with increased suicide risk. In neuronal membranes cholesterol modulates presynaptic and postsynaptic serotonergic neurotransmission. In monkeys dietary cholesterol lowering inhibits central serotonergic activity and predisposes the animals to impulsive and aggressive behaviour. It is speculated that dysregulation of the HPA system and disordered cholesterol metabolism could enhance the serotonergic deficit, thus contributing to a neurobiological vulnerability or diathesis for impulsive and autoaggressive behaviour.

Serial CSF Corticotropin-Releasing Hormone Levels and Adrenocortical Activity in Combat Veterans With Posttraumatic Stress Disorder

The authors sought to carefully test, by using a technique of continuous CSF sampling, the hypothesis that basal elevations in CSF corticotropin-releasing hormone (CRH) concentrations exist in patients with posttraumatic stress disorder (PTSD). They also sought to assess the relationship among PTSD symptoms, adrenocortical activity, and CSF CRH levels. CSF was withdrawn by means of a flexible, indwelling subarachnoid catheter over a 6-hour period, and hourly CSF concentrations of CRH were determined for 11 well-characterized combat veterans with PTSD and 12 matched normal volunteers. Twenty-four-hour urinary-free cortisol excretion was also determined. PTSD and depressive symptoms were correlated with the neuroendocrine data. Mean CSF CRH levels were significantly greater in PTSD patients than in normal subjects (55.2 [SD = 16.4] versus 42.3 pg/ml [SD = 15.6]). No correlation was found between CSF CRH concentrations and PTSD symptoms. While there was no significant difference between groups in 24-hour urinary-free cortisol excretion, the correlation between 24-hour urinary-free cortisol excretion and PTSD symptoms was negative and significant. By using a serial CSF sampling technique, the authors found high basal CSF CRH concentrations and normal 24-hour urinary-free cortisol excretion in combat veterans with PTSD, a combination that appears to be unique among psychiatric conditions studied to date.