Imipramine and alprazolam effects on stress test reactivity in panic disorder

Ambulatory measurement of the ECG T-wave amplitude

Ambulatory recording of the preejection period (PEP) can be used to measure changes in cardiac sympathetic nervous system (SNS) activity under naturalistic conditions. Here, we test the ECG T-wave amplitude (TWA) as an alternative measure, using 24-h ambulatory monitoring of PEP and TWA in a sample of 564 healthy adults. The TWA showed a decrease in response to mental stress and a monotonic decrease from nighttime sleep to daytime sitting and more physically active behaviors. Within-participant changes in TWA were correlated with changes in the PEP across the standardized stressors (r = .42) and the unstandardized naturalistic conditions (mean r = .35). Partialling out changes in heart rate and vagal effects attenuated these correlations, but they remained significant. Ambulatory TWA cannot replace PEP, but simultaneous recording of TWA and PEP provides a more comprehensive picture of changes in cardiac SNS activity in real-life settings.

Differential effects of anxiety and depression on interoceptive accuracy

BACKGROUND

Feedback from the body is assumed to be altered in depression. Nevertheless, empirical studies investigating this assumed relationship remain sparse. This study aimed to examine interrelations between the ability to perceive heartbeats accurately (interoceptive awareness), depressive symptoms, and anxiety in healthy participants.

METHODS

A well-validated heartbeat perception task to measure interoceptive awareness together with two questionnaires indexing anxiety and depression were administered to 119 participants.

RESULTS

As main results we observed a negative correlation between heartbeat perception and depression. Only when focussing on high anxiety levels this negative correlation coefficient between depression and interoception remained significant.

CONCLUSIONS

Our results highlight the possible relationship between depressive symptoms and interoceptive awareness and may have further implications for theoretical models of anxiety disorders and their treatment. Further research is required to examine the potential consequences of altering interoceptive awareness in healthy subjects in relation to depression and anxiety.

Interoceptive awareness mediates the relationship between anxiety and the intensity of unpleasant feelings

This study examined the relationship between interoceptive awareness, anxiety, and the intensity of unpleasant feelings. The perception of visceral signals (interoceptive awareness) plays an important role in the pathophysiology of anxiety disorders. Nevertheless, studies simultaneously investigating relationships between emotion processing, anxiety, and interoceptive awareness remain sparse. The present study was designed to elucidate the interrelations between these variables. Trait anxiety and interoceptive awareness were assessed in 102 healthy participants. Following this, neutral and unpleasant pictures were presented and subjects were asked to rate perceived emotional pleasantness and arousal. We found that both interoceptive awareness and trait anxiety were significantly positively correlated with mean arousal scores for unpleasant pictures. A positive relationship between interoceptive awareness and trait anxiety was also found. Subsequent regression analyses showed that the relationship between emotional arousal and trait anxiety was mediated by differences in interoceptive awareness. Our results highlight the possible role of interoceptive awareness in the development of trait anxiety and may have further implications for theoretical models of anxiety disorders and their treatment.

Neural systems connecting interoceptive awareness and feelings

In many theories of emotions the representations of bodily responses play an important role for subjective feelings. We tested the hypothesis that the perception of bodily states is positively related to the experienced intensity of feelings as well as to the activity of first-order and second-order brain structures involved in the processing of feelings. Using a heartbeat perception task, subjects were separated into groups with either high or poor interoceptive awareness. During emotional picture presentation we measured high-density EEG and used spatiotemporal current density reconstruction to identify regions involved in both interoceptive awareness and emotion processing. We observed a positive relation between interoceptive awareness and the experienced intensity of emotions. Furthermore, the P300 amplitudes to pleasant and unpleasant pictures were enhanced for subjects with high interoceptive awareness. The source reconstruction revealed that interoceptive awareness is related to an enhanced activation in both first-order structures (insula, somatosensory cortices) and second-order structures (anterior cingulate, prefrontal cortices). We conclude that the perception of bodily states is a crucial determinant for the processing and the subjective experience of feelings.

Brain structures involved in interoceptive awareness and cardioafferent signal processing: a dipole source localization study

Afferent signals from the body play an important role for emotional and motivational aspects of behavior. Nevertheless, little is known about the cortical and subcortical structures involved in interoceptive processes. Recently, a functional MRI study demonstrated that insula, somatomotor, and cingulated cortices are activated when subjects focus attention on their heartbeats. Aside from the use of imaging data, cardiac awareness has frequently been studied by using the heartbeat-evoked potential (HEP), a brain wave that appears contingent on the heartbeat. The present study aimed at localizing sources of the HEP. Multichannel EEG was recorded in 44 subjects while they performed a heartbeat perception task. This task was used to quantify interoceptive awareness and to subdivide the subjects into good and poor heartbeat perceivers. Analyses showed highest HEP amplitudes over frontal and frontocentral electrode locations in the time range of later than 200 ms after R-wave onset. By means of a BESA dipole-source-analysis, four sources of the HEP were identified which were located in the anterior cingulate, the right insula, the prefrontal cortex, and the left secondary somatosensory cortex. Good heartbeat perceivers showed both significantly higher HEP amplitudes and higher dipole strength than poor heartbeat perceivers in all four cortical sources. We conclude that the identified structures are involved in the processing of cardiac signals, whereby anterior cingulate and right insula seem to serve as interoceptive centers for cardioception.

Effects of anxiety sensitivity on anxiety and pain during a cold pressor challenge in patients with panic disorder

Fear of anxiety symptoms, or anxiety sensitivity (AS), has been extensively studied in anxiety disorders and more recently has been linked to other psychopathological conditions including pain. Asmundson and colleagues have suggested that AS may act as a risk factor for chronic pain and several studies have demonstrated an association between AS, avoidance behaviors and pain. The present study assessed whether AS levels would be predictive of pain and anxiety during a brief pain induction task. Clinical participants meeting DSM-IV criteria for panic disorder (n = 22) were age and sex matched with nonclinical controls (n = 22) and exposed to a 2-min cold pressor challenge. Diagnostic status and AS were significantly predictive of pain and anxiety during the cold pressor task. Moreover, AS appears to mediate the relationship between diagnostic status and pain. However, AS appears to be only indirectly associated with pain through its contribution to anxiety.

Pharmacologic effect of imipramine, paroxetine, and sertraline on 35% carbon dioxide hypersensitivity in panic patients: a double-blind, random, placebo-controlled study

The effects of short treatment (7 days) with the tricyclic antidepressant imipramine and the two selective serotonin reuptake inhibitors paroxetine and sertraline on the reactivity to inhalation of 35% CO2/65% O2 were compared in 70 panic patients who had positive responses to 35% CO2 inhalations. A double-blind, random, placebo-controlled design was applied. Each patient was given the 35% CO2 challenge on days 0 (before starting the treatment), 3, and 7. In the placebo group, there were no significant changes in the reactivity to 35% CO2 in the three sessions whereas there were significant similar reductions of reactivity to 35% CO2 in all three drug-treated groups. These results confirm the good reproducibility of 35% CO2 reactivity and the negligible effects of placebo on reactivity to CO2 and suggest that short treatments with imipramine, paroxetine, and sertraline decrease reactivity to 35% CO2, possibly as an expression of their antipanic properties.

Lack of effect of laboratory-provoked anxiety on plasma homovanillic acid concentration in normal subjects

The present study was undertaken to investigate if acute anxiety can affect plasma concentrations of homovanillic acid (pHVA). Since elevated pHVA levels have been associated with severity of schizophrenic symptoms, the results of this study will help determine if the pHVA elevations are directly related to psychosis or if anxiety is also a contributory factor. Anxiety was provoked in 10 young normal subjects by a combined paradigm of mental arithmetic task and threat of electrical shock. A significant increase in self-ratings of anxiety, blood pressure, and plasma levels of norepinephrine, 3-methoxy-4-hydroxyphenylethyleneglycol and growth hormone indicated that the paradigm used was effective in provoking anxiety; however, anxiety did not affect pHVA concentrations. The results may support the notion that increased pHVA levels in severely ill schizophrenic patients are related to the schizophrenic pathophysiology rather than to anxiety.

Predator-elicited flight responses in Swiss-Webster mice: an experimental model of panic attacks

1. The nosological status of panic disorder is still a matter of debate. Nevertheless, evidence is emerging that panic attacks have a different pattern of drug responsiveness from other forms of anxiety. 2. Several experimental animal models of panic attacks have been developed. These vary in the extent to which they meet criteria for face validity, predictive validity and construct validity, normally applied to such models. 3. In the present review, the authors examine the possibility that predator-elicited flight responses in Swiss-Webster mice might serve as an experimental model for the screening of panic-modulating drugs. 4. Drug effects on flight responses clearly indicate that this model has good predictive validity as panic-promoting agents increase flight reactions, while panicolytic drug challenge induces opposite effects. In addition, drugs devoid of any effect on panic attack, also do not alter flight behavior. 5. These findings strongly suggest that the model of predator-elicited flight responses in Swiss-Webster mice is useful for the investigation of panic-modulating drugs.

Lactate-induced anxiety after imipramine and diazepam treatment

To examine the effect of treatment on lactate-induced anxiety in a controlled study, we infused 44 panic disorder patients with lactate and placebo before and after eight weeks of double-blind treatment with imipramine, diazepam, or placebo. During treatment, both imipramine and diazepam groups improved more than the placebo group. After treatment, patients in both the imipramine and diazepam groups had significantly less anxiety than the placebo patients when reinfused with lactate. In addition, imipramine decreased posttreatment panic attack frequency and diazepam decreased the perceived severity of posttreatment lactate-induced panic attacks. This study demonstrates that diazepam, like imipramine, is an effective treatment for panic disorder, and that both imipramine and diazepam blunt lactate-induced anxiety in a placebo controlled study.