Startle reflex studies in rodents indicate that female are more reactive than rats in experimental models of sustained anxiety but not in models of phasic fear (Toufexis, 2007). This study examined evidence for a similar effect in humans. Participants were exposed to three conditions, (1) predictable aversive shocks signaled by a cue, (2) unpredictable shocks, and (3) no shocks. Acoustic startle stimuli were delivered regularly across conditions. Phasic startle potential to the threat cue in the predictable condition was not affected by sex. In contrast, and consistent with basic research, the sustained increase in startle in the predictable and unpredictable conditions was greater in women compared to men. Animal studies suggest that such an effect may be mediated by the effects of sexual dimorphism in limbic structures, including the bed nucleus of the stria terminalis. However, psychosocial factors may also contribute to this effect.
fear; anxiety; sex difference; startle; unpredictability
Fearful faces readily activate the amygdala. Yet, whether fearful faces evoke fear is unclear. Startle studies show no potentiation of startle by fearful faces, suggesting that such stimuli do not activate defense mechanisms. However, the response to biologically relevant stimuli may be sensitized by anxiety. The present study tested the hypothesis that startle would not be potentiated by fearful faces in a safe context, but that startle would be larger during fearful faces compared to neutral faces in a threat-of-shock context. Subjects viewed fearful and neutral faces in alternating periods of safety and threat of shock. Acoustic startle stimuli were presented in the presence and absence of the faces. Startle was transiently potentiated by fearful faces compared to neutral faces in the threat periods. This suggests that although fearful faces do not prompt behavioral mobilization in an innocuous context, they can do so in an anxiogenic one.
Fear; Anxiety; Startle reflex; Fearful face
Fear-potentiated startle is defined as an increase in the magnitude of the startle reflex in the presence of a stimulus that was previously paired with an aversive event. It has been proposed that a subject’s awareness of the contingencies in the experiment may affect fear-potentiated startle. The authors adapted a conditional discrimination procedure (AX+/BX−), previously validated in animals, to a human fear-potentiated startle paradigm in 50 healthy volunteers. This paradigm allows for an assessment of fear-potentiated startle during threat conditions as well as inhibition of fear-potentiated startle during safety conditions. A response keypad was used to assess contingency awareness on a trial-by-trial basis. Both aware and unaware subjects showed fear-potentiated startle. However, awareness was related to stimulus discrimination and fear inhibition.
human startle response; contingency awareness; discrimination learning; fear inhibition
Fear conditioning methodologies have often been employed as testable models for assessing learned fear responses in individuals with anxiety disorders such as post-traumatic stress disorder (PTSD) and specific phobia. One frequently used paradigm is measurement of the acoustic startle reflex under conditions that mimic anxiogenic and fear-related conditions. For example, fear-potentiated startle is the relative increase in the frequency or magnitude of the acoustic startle reflex in the presence of a previously neutral cue (e.g., colored shape; termed the conditioned stimulus or CS+) that has been repeatedly paired with an aversive unconditioned stimulus (e.g., airblast to the larynx). Our group has recently used fear-potentiated startle paradigms to demonstrate impaired fear extinction in civilian and combat populations with PTSD. In the current study, we examined the use of either auditory or visual CSs in a fear extinction protocol that we have validated and applied to human clinical conditions. This represents an important translational bridge in that numerous animal studies of fear extinction, upon which much of the human work is based, have employed the use of auditory CSs as opposed to visual CSs. Participants in both the auditory and visual groups displayed robust fear-potentiated startle to the CS+, clear discrimination between the reinforced CS+ and non-reinforced CS−, significant extinction to the previously reinforced CS+, and marked spontaneous recovery. We discuss the current results as they relate to future investigations of PTSD-related impairments in fear processing in populations with diverse medical and psychiatric histories.
fear conditioning; acoustic startle; auditory; extinction; discrimination; human
Abnormalities in both cortisol and dehydroepiandrosterone (DHEA) have been reported in psychiatric disorders. Analysis of saliva, urine and blood cortisol and DHEA levels provides an index of hormone levels over a short time period. Unlike such conventional measures, fingernails incorporate endogenous hormones that passively diffuse to the nail matrix from capillaries during keratinization. This study piloted the measurement of cortisol and DHEA levels in fingernails as a potential measure of their accumulated secretion of steroid hormones over a prolonged time period.
Thirty-three university students (18–24 years) provided fingernail samples on two occasions over a school semester. The visits were scheduled so nail cortisol and DHEA levels were collected from periods when students might be under different levels of stress.
During the putatively stressful period, the nail samples showed a significant increase in the cortisol: DHEA ratio (P = 0.0002) due to a significant decrease in the DHEA levels (P = 0.004) and a numerical but not statistically significant increase in the cortisol levels (P = 0.256).
This pilot study showed that nails can be used to measure cortisol and DHEA, a measure which may reflect environmental stress. More work is required to further validate this technique which may prove useful in studies of both healthy individuals and patient groups.
stress; nails; cortisol; DHEA
Tuberculosis (TB) remains the most frequent cause of illness and death from an infectious agent, and its interaction with HIV has devastating effects. We determined plasma levels of dehydroepiandrosterone (DHEA), its circulating form DHEA-suphate (DHEA-s) and cortisol in different stages of M. tuberculosis infection, and explored their role on the Th1 and Treg populations during different scenarios of HIV-TB coinfection, including the immune reconstitution inflammatory syndrome (IRIS), a condition related to antiretroviral treatment. DHEA levels were diminished in HIV-TB and HIV-TB IRIS patients compared to healthy donors (HD), HIV+ individuals and HIV+ individuals with latent TB (HIV-LTB), whereas dehydroepiandrosterone sulfate (DHEA-s) levels were markedly diminished in HIV-TB IRIS individuals. HIV-TB and IRIS patients presented a cortisol/DHEA ratio significantly higher than HIV+, HIV-LTB and HD individuals. A positive correlation was observed between DHEA-s and CD4 count among HIV-TB individuals. Conversely, cortisol plasma level inversely correlated with CD4 count within HIV-TB individuals. M. tuberculosis-specific Th1 lymphocyte count was increased after culturing PBMC from HIV-TB individuals in presence of DHEA. We observed an inverse correlation between DHEA-s plasma level and Treg frequency in co-infected individuals, and CD4+FoxP3+ Treg frequency was increased in HIV-TB and IRIS patients compared to other groups. Strikingly, we observed a prominent CD4+CD25-FoxP3+ population across HIV-TB and HIV-TB IRIS patients, which frequency correlated with DHEA plasma level. Finally, DHEA treatment negatively regulated FoxP3 expression without altering Treg frequency in co-infected patients. These data suggest an enhancing role for DHEA in the immune response against M. tuberculosis during HIV-TB coinfection and IRIS.
DHEA and DHEAS are steroids synthesized in human adrenals, but their function is unclear. In addition to adrenal synthesis, evidence also indicates that DHEA and DHEAS are synthesized in the brain, further suggesting a role of these hormones in brain function and development. Despite intensifying research into the biology of DHEA and DHEAS, many questions concerning their mechanisms of action and their potential involvement in neuropsychiatric illnesses remain unanswered. We review and distill the preclinical and clinical data on DHEA and DHEAS, focusing on (i) biological actions and putative mechanisms of action, (ii) differences in endogenous circulating concentrations in normal subjects and patients with neuropsychiatric diseases, and (iii) the therapeutic potential of DHEA in treating these conditions. Biological actions of DHEA and DHEAS include neuroprotection, neurite growth, and antagonistic effects on oxidants and glucocorticoids. Accumulating data suggest abnormal DHEA and/or DHEAS concentrations in several neuropsychiatric conditions. The evidence that DHEA and DHEAS may be fruitful targets for pharmacotherapy in some conditions is reviewed.
Dehydroepiandrosterone; DHEA; DHEAS; neuroprotection; neurogenesis; apoptosis; depression; schizophrenia; dementia; cortisol
The amplitude of the acoustic startle response is increased when elicited in the presence of brief cues that predict shock (fear-potentiated startle) and also when elicited during sustained exposure to bright light (light-enhanced startle). Although both effects are thought to reflect fear or anxiety, their neuroanatomical substrates differ. Whereas fear-potentiated startle is disrupted by reversible inactivation of the central nucleus of the amygdala (CeA) but not the closely related bed nucleus of the stria terminalis (BNST), light-enhanced startle is disrupted by BNST inactivation but not by CeA inactivation. Intra-ventricular infusions of corticotropin releasing factor (CRF) also increase startle (CRF-enhanced startle) and this effect is mediated by CRF receptors within the BNST, with no involvement of the CeA. Together, these observations suggest that CeA- and BNST-dependent fear and anxiety may be differentially sensitive to CRF receptor blockade. We tested this by orally administering the novel, potent, and selective CRF-R1 antagonist GSK876008 to rats prior to CRF-enhanced, light-enhanced, or fear-potentiated startle testing. GSK876008 disrupted CRF-enhanced startle with a linear dose-response curve, and light-enhanced startle with a U-shaped dose-response curve, but did not disrupt fear-potentiated startle to a visual stimulus at any dose tested, and even augmented the response in some animals. GSK876008 also disrupted shock-related ‘baseline’ startles increases, which may have reflected context conditioning (shown elsewhere to also be BNST-dependent). Overall, these results suggest that short-duration CeA-dependent threat responses can be pharmacologically dissociated from longer-duration BNST-dependent responses in terms of their sensitivity to CRF1 receptor antagonists.
fear; anxiety; startle; amygdala; bed nucleus of the stria terminalis; corticotropin releasing factor
Oxytocin is known to have anti-anxiety and anti-stress effects. Using a fear-potentiated startle paradigm in rats, we previously demonstrated that subcutaneously administered oxytocin suppressed acoustic startle following fear conditioning compared with startle before fear conditioning (termed background anxiety), but did not have an effect on cue-specific fear-potentiated startle. The findings suggest oxytocin reduces background anxiety, an anxious state not directly related to cue-specific fear, but sustained beyond the immediate threat. The goal of the present study was to compare the effects of centrally and peripherally administered oxytocin on background anxiety and cue-specific fear. Male rats were given oxytocin either subcutaneously (SC) or intracerebroventricularly (ICV) into the lateral ventricles before fear-potentiated startle testing. Oxytocin doses of 0.01 and 0.1 μg/kg SC reduced background anxiety. ICV administration of oxytocin at doses from 0.002 to 20 μg oxytocin had no effect on background anxiety or cue-specific fear-potentiated startle. The 20 μg ICV dose of oxytocin did reduce acoustic startle in non-fear conditioned rats. These studies indicate that oxytocin is potent and effective in reducing background anxiety when delivered peripherally, but not when delivered into the cerebroventricular system. Oxytocin given systemically may have anti-anxiety properties that are particularly germane to the hypervigilance and exaggerated startle typically seen in many anxiety and mental health disorder patients.
oxytocin; anxiety; fear; startle; PTSD; mood/anxiety/stress disorders; neuropeptides; learning & memory; animal models; oxytocin; fear; startle; PTSD
Posttraumatic stress disorder (PTSD) patients show heightened fear responses to trauma reminders and an inability to inhibit fear in the presence of safety reminders. Brain imaging studies suggest that this is in part due to amygdala over-reactivity as well as deficient top-down cortical inhibition of the amygdala. Consistent with these findings, previous studies, using fear-potentiated startle (FPS), have shown exaggerated startle and deficits in fear inhibition in PTSD participants. However, many PTSD studies using the skin conductance response (SCR) report no group differences in fear acquisition.
The study included 41 participants with PTSD and 70 without PTSD. The fear conditioning session included a reinforced conditioned stimulus (CS+, danger cue) paired with an aversive airblast, and a nonreinforced CS (CS−, safety cue). Acoustic startle responses and SCR were acquired during the presentation of each CS.
The results showed that fear conditioned responses were captured in both the FPS and SCR measures. Furthermore, PTSD participants had higher FPS to the danger cue and safety cue compared to trauma controls. However, SCR did not differ between groups. Finally, we found that FPS to the danger cue predicted re-experiencing symptoms, whereas FPS to the safety cue predicted hyper-arousal symptoms. However, SCR did not contribute to PTSD symptom variance.
Replicating earlier studies, we showed increased FPS in PTSD participants. However, although SCR was a good measure of differential conditioning, it did not differentiate between PTSD groups. These data suggest that FPS may be a useful tool for translational research.
Fear-potentiated startle; skin conductance response; trauma; posttraumatic stress disorders; psychophysiology
Preclinical data indicates that threat stimuli elicit two classes of defensive behaviors, those that are associated with imminent danger and are characterized by avoidance or fight (fear), and those that are associated with temporally uncertain danger and are characterized by sustained apprehension and hypervigilance (anxiety).
To 1) review evidence for a distinction between fear and anxiety in animal and human experimental models using the startle reflex as an operational measure of aversive states, 2) describe experimental models of anxiety, as opposed to fear, in humans, 3) examine the relevance of these models to clinical anxiety.
The distinction between phasic fear to imminent threat and sustained anxiety to temporally uncertain danger is suggested by psychopharmacological and behavioral evidence from ethological studies and can be traced back to distinct neuroanatomical systems, the amygdala and the bed nucleus of the stria terminalis. Experimental models of anxiety, not fear, are relevant to non-phobic anxiety disorders.
Progress in our understanding of normal and abnormal anxiety is critically dependent on our ability to model sustained aversive states to temporally uncertain threat.
Startle; fear-potentiated startle; fear; anxiety; experimental models; anxiety disorders
The ability to identify predictors of aversive events allows organisms to appropriately respond to these events, and failure to acquire these fear contingencies can lead to maladaptive contextual anxiety. Recently, preclinical studies demonstrated that the corticotropin-releasing factor and serotonin systems are interactively involved in adaptive fear acquisition. Here, 150 healthy medication-free human subjects completed a cue and context fear conditioning procedure in a virtual reality environment. Fear potentiation of the eyeblink startle reflex (FPS) was measured to assess both uninstructed fear acquisition and instructed fear expression. All participants were genotyped for polymorphisms located within regulatory regions of the corticotropin releasing hormone receptor 1 (CRHR1 - rs878886) and the serotonin transporter (5HTTLPR). These polymorphisms have previously been linked to panic disorder and anxious symptomology and personality, respectively. G-allele carriers of CRHR1 (rs878886) showed no acquisition of fear conditioned responses (FPS) to the threat cue in the uninstructed phase, whereas fear acquisition was present in C/C homozygotes. Moreover, carrying the risk alleles of both rs878886 (G-allele) and 5HTTLPR (short allele) was associated with increased FPS to the threat context during this phase. After explicit instructions regarding the threat contingency were given, the cue FPS and context FPS normalized in all genotype groups. The present results indicate that genetic variability in the corticotropin-releasing hormone receptor 1, especially in interaction with the 5HTTLPR, is involved in the acquisition of fear in humans. This translates prior animal findings to the human realm.
This study examined the effects of oral administration of 20 mg hydrocortisone on baseline and fear-potentiated startle in 63 male veterans with or without PTSD. The procedure was based on a two-session, within-subject design in which acoustic startle eyeblink responses were recorded during intervals of threat or no threat of electric shock. Results showed that the magnitude of the difference between startle responses recorded during anticipation of imminent shock compared to “safe” periods was reduced after hydrocortisone administration relative to placebo. This effect did not vary as a function of PTSD group nor were there were any significant group differences in other indices startle amplitude. Findings suggest that the acute elevations in systemic cortisol produced by hydrocortisone administration may have fear-inhibiting effects. This finding may have implications for understanding the role of hypothalamic-pituitary-adrenal (HPA)-axis function in vulnerability and resilience to traumatic stress.
Alterations in hormone concentrations, including adrenocorticotropin, corticotropin releasing hormone, and cortisol have been reported in patients with obsessive compulsive disorder (OCD). Dehydroepiandrosterone (DHEA) and its sulfated metabolite, DHEA-S, have not been assessed in patients with OCD. We report 24-hour serum DHEA, DHEA-S, and cortisol concentrations in a young man with OCD and 15 healthy young men. Circadian patterns of DHEA and cortisol were markedly different in the subject with OCD than in the control subjects. DHEA and DHEA-S concentrations were substantially higher in the OCD subject than in the control subjects. In contrast, cortisol concentrations were similar in the OCD subject and the control subjects. Future clinical studies are needed to evaluate the significance of DHEA and DHEA-S in OCD.
Fear of pain and its relationship to dental fear was investigated by measuring autonomic reactions (skin conductance and heart rate) in individuals reporting high and low dental fear when in the presence of a cue that threatened the presentation of electric shock ("threat') or not ("safe"). Acoustic startle probes were also presented during both threat and safe periods, and the reflexive eye blink, the skin conductance response, and cardiac changes to the startle probe measured. All participants reacted with greater defensive reactivity, including potentiated startle blinks, heightened skin conductance, and cardiac deceleration in the context of threat, compared to safe, cues. Individuals reporting high dental fear were significantly more reactive during threat periods, compared to low fear individuals, showing larger blink reflexes and heightened electrodermal activity, as well as heightened autonomic responses to the startle probe itself. Individual differences in defensive reactivity persisted even after participants received a single mild shock halfway through the experiment. The data indicate that threat of shock elicits heightened defensive reactivity in those reporting high dental fear, consistent with the hypothesis that fear of potentially painful events may be a potent mediator of the anxiety involved in anticipated medical and dental treatment.
To provide insight into individual differences in fear learning, we examined the emotional and cognitive expressions of discriminative fear conditioning in direct relation to its neural substrates. Contrary to previous behavioral–neural (fMRI) research on fear learning—in which the emotional expression of fear was generally indexed by skin conductance—we used fear-potentiated startle, a more reliable and specific index of fear. While we obtained concurrent fear-potentiated startle, neuroimaging (fMRI), and US-expectancy data, healthy participants underwent a fear-conditioning paradigm in which one of two conditioned stimuli (CS+ but not CS–) was paired with a shock (unconditioned stimulus [US]). Fear learning was evident from the differential expressions of fear (CS+ > CS–) at both the behavioral level (startle potentiation and US expectancy) and the neural level (in amygdala, anterior cingulate cortex, hippocampus, and insula). We examined individual differences in discriminative fear conditioning by classifying participants (as conditionable vs. unconditionable) according to whether they showed successful differential startle potentiation. This revealed that the individual differences in the emotional expression of discriminative fear learning (startle potentiation) were reflected in differential amygdala activation, regardless of the cognitive expression of fear learning (CS–US contingency or hippocampal activation). Our study provides the first evidence for the potential of examining startle potentiation in concurrent fMRI research on fear learning.
Discriminative fear learning; Fear-potentiated startle; fMRI; Amygdala; Hippocampus; Deconvolution; Individual differences; Anxiety
The present study examined the effects of sustained anticipatory anxiety on the affective modulation of the eyeblink startle reflex. Towards this end, pleasant, neutral and unpleasant pictures were presented as a continuous stream during alternating threat-of-shock and safety periods, which were cued by colored picture frames. Orbicularis-EMG to auditory startle probes and electrodermal activity were recorded. Previous findings regarding affective picture valence and threat-of-shock modulation were replicated. Of main interest, anticipating aversive events and viewing affective pictures additively modulated defensive activation. Specifically, despite overall potentiated startle blink magnitude in threat-of-shock conditions, the startle reflex remained sensitive to hedonic picture valence. Finally, skin conductance level revealed sustained sympathetic activation throughout the entire experiment during threat- compared to safety-periods. Overall, defensive activation by physical threat appears to operate independently from reflex modulation by picture media. The present data confirms the importance of simultaneously manipulating phasic-fear and sustained-anxiety in studying both normal and abnormal anxiety.
Mental fatigue, cognitive disorders, and sleep disturbances seen in chronic fatigue syndrome (CFS) may be attributed to cholinergic deficit. A functional deficiency of cholinergic neurotransmission may cause the hypothalamic-pituitary-adrenal axis hypoactivity seen in CFS. Therefore, we investigated the alterations in stress hormones such as cortisol and dehydroepiandrosterone sulfate (DHEAS) in CFS patients before and after 4-week administration of galantamine hydrobromide, a selective acetylcholinesterase inhibitor, and aimed to investigate whether there are any relationships between the probable hormonal changes and cholinergic treatment.
Basal levels of cortisol and DHEAS were measured in 29 untreated CFS patients who were diagnosed according to Centers for Disease Control (CDC) criteria and in 20 healthy controls. In the patient group, four weeks after 8 mg/d galantamine hydrobromide treatment, cortisol and DHEAS levels were measured again. After the treatment 22 patients who stayed in study were divided into two subgroups as responders and nonresponders according to the reduction in their Newcastle Research Group ME/CFS Score Card (NRG) scores.
Important findings of this study are lower pre-and post-treatment cortisol levels and in all CFS patients compared to controls (F=4.129, p=0.049; F=4.803, p=0.035, respectively); higher basal DHEAS values and higher DHEAS/cortisol molar ratios which were normalized following four weeks' treatment with 8 mg/d galantamine hydrobromide in the treatment-respondent group (F=5.382, p=0.029; F=5.722, p=0.025, respectively).
The findings of the decrease in basal DHEAS levels and DHEAS/cortisol molar ratios normalizing with galantamine treatment may give some support to the cholinergic deficit hypothesis in CFS.
Chronic fatigue syndrome; Cortisol; Dehydroepiandrosterone sulfate; Galantamine hydrobromide
Research has highlighted the need for new methods to assess emotions in children on multiple levels in order to gain better insight into the complex processes of emotional development. The startle reflex is a unique translational tool that has been utilized to study physiological processes during fear and anxiety in rodents and in human subjects. However, it has been challenging to implement developmentally-appropriate startle experiments in children. This paper describes a procedure that uses predictable and unpredictable aversive events to distinguish between phasic fear and sustained anxiety in children and adolescents. We investigated anxious responses, as measured with the startle reflex, in youth (N = 36, mean age[range] = 12.63 [7–17]) across three conditions: no aversive events (N), predictable aversive events (P), and unpredictable aversive events (U). Short-duration cues were presented several times in each condition. Aversive events were signaled by the cues in P, but were presented randomly in U. Participants showed fear-potentiated startle to the threat cue in P. Startle responses were also elevated between cues in U compared to N, suggesting that unpredictable aversive events can evoke a sustained state of anxiety in youth. This latter effect was influenced by sex, being greater in girls compared to boys. These findings indicate the feasibility of this experimental induction of the startle reflex in response to predictable and unpredictable events in children and adolescents, enabling future research on inter-individual differences in fear and anxiety and their development in youth.
fear; anxiety; unpredictability; psychophysiology; startle reflex; sex differences
Background: Posttraumatic stress disorder (PTSD) patients show heightened fear responses to trauma reminders and an inability to inhibit fear in the presence of safety reminders. Brain imaging studies suggest that this is in part due to amygdala over-reactivity as well as deficient top-down cortical inhibition of the amygdala. Consistent with these findings, previous studies, using fear-potentiated startle (FPS), have shown exaggerated startle and deficits in fear inhibition in PTSD participants. However, many PTSD studies using the skin conductance response (SCR) report no group differences in fear acquisition. Method: The study included 41 participants with PTSD and 70 without PTSD. The fear conditioning session included a reinforced conditioned stimulus (CS+, danger cue) paired with an aversive airblast, and a nonreinforced conditioned stimulus (CS−, safety cue). Acoustic startle responses and SCR were acquired during the presentation of each CS. Results: The results showed that fear conditioned responses were captured in both the FPS and SCR measures. Furthermore, PTSD participants had higher FPS to the danger cue and safety cue compared to trauma controls. However, SCR did not differ between groups. Finally, we found that FPS to the danger cue predicted re-experiencing symptoms, whereas FPS to the safety cue predicted hyper-arousal symptoms. However, SCR did not contribute to PTSD symptom variance. Conclusions: Replicating earlier studies, we showed increased FPS in PTSD participants. However, although SCR was a good measure of differential conditioning, it did not differentiate between PTSD groups. These data suggest that FPS may be a useful tool for translational research. Depression and Anxiety, 2011. © 2011 Wiley Periodicals, Inc.
fear-potentiated startle; skin conductance response; trauma; posttraumatic stress disorders; psychophysiology
Diurnal variation of baseline startle amplitude was examined in 14 normal inpatients on a research unit where behavioral activity and environmental stimuli were highly controlled. We tested a hypothesized association between diurnal variations of salivary cortisol and reflex amplitude by recording acoustic startle eyeblinks shortly before bedtime, when cortisol was near its lowest daily level, and just after awakening, when cortisol was at its peak. Results showed that startle eyeblinks were greater during evening than morning sessions, whereas the opposite was true for cortisol levels. Skin conductance levels and reaction time performance also increased from morning to evening. These findings are consistent with accumulating evidence suggesting a possible link between startle reactivity and hypothalamic-pituitary-adrenal axis activity, and an association between diurnal variations in endogenous arousal and startle amplitude.
Startle; Circadian rhythm; Diurnal; Cortisol
Dehydroepiandrosterone sulfate (DHEAS) is a steroid hornone that is synthesized, de novo, in the brain. Endogenous DHEAS levels correlate with the quality of mental and physical health, where the highest levels of DHEAS occur in healthy young adults and reduced levels of DHEAS are found with advanced age, disease, or extreme stress. DHEAS supplementation, therefore, may serve as a therapeutic agent against a broad range of maladies. This paper summarizes laboratory findings on dose-response relationships between DHEAS and cognitive and electrophysiological measures of hippocampal functioning. It was found that a low, but not a high, dose of DHEAS enhanced hippocampal primed burst potentiation (a physiological model of memory) as well as spatial (hippocampal-dependent) memory in rats. This complex dose-response function of DHEAS effects on the brain and memory may contribute toward the inconsistent findings that have been obtained by other investigators in studies on DHEAS administration in people.
neurosteroid; dehydroepiandrosterone; DHEA; hippocampus; long-term potentiation; memory
Background: In rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE), patients demonstrate low levels of adrenal hormones.
Objective: To investigate whether increased renal clearance and daily excretion contribute to this phenomenon.
Methods: Thirty patients with RA, 32 with SLE, and 54 healthy subjects (HS) participated. Serum and urinary levels of cortisol, cortisone, 17-hydroxyprogesterone (17OHP), androstenedione, dehydroepiandrosterone (DHEA), and DHEA sulphate (DHEAS) were measured.
Results: Clearance of DHEAS and DHEA was lower in patients than in HS, and clearance of androstenedione was somewhat higher in patients than in HS, but daily excretion of this latter hormone was low. Clearance of cortisol, cortisone, and 17OHP was similar between the groups. The total molar amount per hour of excreted DHEA, DHEAS, and androstenedione was lower in patients than HS (but similar for cortisol). Serum DHEAS levels correlated with urinary DHEAS levels in HS and patients, whereby HS excreted 5–10 times more of this hormone than excreted by patients. Low serum levels of adrenal androgens and cortisol in patients as compared with HS were confirmed, and proteinuria was not associated with changes of measured renal parameters.
Conclusions: This study in patients with RA and SLE demonstrates that low serum levels of adrenal androgens and cortisol are not due to increased renal clearance and daily loss of these hormones. Decreased adrenal production or increased conversion or conjugation to downstream hormones are the most likely causes of inadequately low serum levels of adrenal hormones in RA and SLE.
Predictability is a fundamental modulator of anxiety in that the ability to predict aversive events mitigates anxious responses. In panic disorder, persistent symptoms of anxiety are caused by anticipation of the next uncued (unpredictable) panic attack. The authors tested the hypothesis that elevated anxious reactivity, specifically toward unpredictable aversive events, is a psychophysiological correlate of panic disorder.
Participants were exposed to one condition in which predictable aversive stimuli were signaled by a cue, a second condition in which aversive stimuli were administered unpredictably, and a third condition in which no aversive stimuli were anticipated. Startle was used to assess anxious responses to cues and contexts.
Relative to healthy comparison subjects, patients with panic disorder displayed equivalent levels of fear-potentiated startle to the threat cue but elevated startle potentiation in the context of the unpredictable condition.
Patients with panic disorder are overly sensitive to unpredictable aversive events. This vulnerability could be either a premorbid trait marker of the disorder or an acquired condition caused by the experience of uncued panic attacks. As a premorbid trait, vulnerability to unpredictability could be etiologically related to panic disorder by sensitizing an individual to danger, ultimately leading to intense fear/alarm responses to mild threats. As an acquired characteristic, such vulnerability could contribute to the maintenance and worsening of panic disorder symptoms by increasing anticipatory anxiety.
Anxiety is a common symptom of nicotine withdrawal in humans, and may predict an inability to abstain from cigarette smoking. It is not clear if self-reports of anxiety during abstinence reflect increased baseline anxiety and/or increased responses to exogenous stressors. We hypothesized that nicotine withdrawal selectively exacerbates reactivity to aversive stimuli in rodents. Here, we investigated the effect of withdrawal from chronic nicotine administration (3.16 mg/kg per day base, delivered via subcutaneous osmotic minipumps) in the light-enhanced startle (LES) test in Wistar rats. In this procedure, baseline startle responding in the dark is compared to startle responding when the chamber is brightly lit. Bright illumination is aversive for rats and potentiates the startle response. Hence, this procedure allows comparisons of withdrawal effects on startle reactivity between relatively neutral and stressful contexts. We found that spontaneous nicotine withdrawal (24 h post-pump removal) did not influence baseline startle responding, but produced a selective increase in LES. Precipitated nicotine withdrawal through injections of one of two nicotinic acetylcholine receptor (nAChR) antagonists, dihydro-β-erythroidine hydrobromide (DHβE: 0, 1.5, 3, or 6 mg/kg) or mecamylamine (0, 1, 2, or 4 mg/kg), did not influence baseline startle responding or LES. These results suggest that spontaneous nicotine withdrawal selectively potentiates responses to anxiogenic stimuli, but does not by itself produce a strong anxiogenic effect. These findings support the hypothesis that nicotine withdrawal exacerbates stress responding, and indicate LES may be a useful model to examine withdrawal effects on anxiety.
nicotine; withdrawal; anxiety; startle; rat