Search for pathophysiology of panic disorder

Single-Nucleus Transcriptome Profiling from the Hippocampus of a PTSD Mouse Model and CBD-Treated Cohorts

Post-traumatic stress disorder (PTSD) is the most common psychiatric disorder after a catastrophic event; however, the efficacious treatment options remain insufficient. Increasing evidence suggests that cannabidiol (CBD) exhibits optimal therapeutic effects for treating PTSD. To elucidate the cell-type-specific transcriptomic pathology of PTSD and the mechanisms of CBD against this disease, we conducted single-nucleus RNA sequencing (snRNA-seq) in the hippocampus of PTSD-modeled mice and CBD-treated cohorts. We constructed a mouse model by adding electric foot shocks following exposure to single prolonged stress (SPS+S) and tested the freezing time, anxiety-like behavior, and cognitive behavior. CBD was administrated before every behavioral test. The PTSD-modeled mice displayed behaviors resembling those of PTSD in all behavioral tests, and CBD treatment alleviated all of these PTSD-like behaviors (n = 8/group). Three mice with representative behavioral phenotypes were selected from each group for snRNA-seq 15 days after the SPS+S. We primarily focused on the excitatory neurons (ExNs) and inhibitory neurons (InNs), which accounted for 68.4% of the total cell annotations. A total of 88 differentially upregulated genes and 305 differentially downregulated genes were found in the PTSD mice, which were found to exhibit significant alterations in pathways and biological processes associated with fear response, synaptic communication, protein synthesis, oxidative phosphorylation, and oxidative stress response. A total of 63 overlapping genes in InNs were identified as key genes for CBD in the treatment of PTSD. Subsequent Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses revealed that the anti-PTSD effect of CBD was related to the regulation of protein synthesis, oxidative phosphorylation, oxidative stress response, and fear response. Furthermore, gene set enrichment analysis (GSEA) revealed that CBD also enhanced retrograde endocannabinoid signaling in ExNs, which was found to be suppressed in the PTSD group. Our research may provide a potential explanation for the pathogenesis of PTSD and facilitate the discovery of novel therapeutic targets for drug development. Moreover, it may shed light on the therapeutic mechanisms of CBD.

On Understanding the Being of Panic Disorder Patients

Four different hypothetical phases of the “understanding” that panic disorder (PD) patients seem to go through are presented. The understanding here consists of both “to understand” and “to be understood.” The four phases are divided along with the general course of PD and experiences of the patients in general: (a) naming: diagnosis, (b) knowing: agreeing on the explanation of the mechanism, (c) objectifying: confrontation and control, and (d) surviving: holding the subjective experience of living with “pain” with or without meaning/understanding. The goal of this article is to offer clinical insights helpful in understanding PD by shedding light on different dimensions of the “being” of PD patients.

Olfactory Hallucinations without Clinical Motor Activity: A Comparison of Unirhinal with Birhinal Phantosmia

Olfactory hallucinations without subsequent myoclonic activity have not been well characterized or understood. Herein we describe, in a retrospective study, two major forms of olfactory hallucinations labeled phantosmias: one, unirhinal, the other, birhinal. To describe these disorders we performed several procedures to elucidate similarities and differences between these processes. From 1272, patients evaluated for taste and smell dysfunction at The Taste and Smell Clinic, Washington, DC with clinical history, neurological and otolaryngological examinations, evaluations of taste and smell function, EEG and neuroradiological studies 40 exhibited cyclic unirhinal phantosmia (CUP) usually without hyposmia whereas 88 exhibited non-cyclic birhinal phantosmia with associated symptomology (BPAS) with hyposmia. Patients with CUP developed phantosmia spontaneously or after laughing, coughing or shouting initially with spontaneous inhibition and subsequently with Valsalva maneuvers, sleep or nasal water inhalation; they had frequent EEG changes usually ipsilateral sharp waves. Patients with BPAS developed phantosmia secondary to several clinical events usually after hyposmia onset with few EEG changes; their phantosmia could not be initiated or inhibited by any physiological maneuver. CUP is uncommonly encountered and represents a newly defined clinical syndrome. BPAS is commonly encountered, has been observed previously but has not been clearly defined. Mechanisms responsible for phantosmia in each group were related to decreased gamma-aminobutyric acid (GABA) activity in specific brain regions. Treatment which activated brain GABA inhibited phantosmia in both groups.

Predictors of response among patients with panic disorder treated with medications in a naturalistic follow-up: the role of adult separation anxiety

BACKGROUND

Efficacy of treatments for panic disorder is well established, but not all patients respond. Adult separation anxiety has been found to predict poorer response to CBT, but its effect on response to medication has not been previously explored.

STUDY AIM

The aim of this study is to investigate if panic-agoraphobic spectrum factors, including 'separation anxiety' factor predict treatment outcome in patients with panic disorder.

STUDY SAMPLE

Participants who met criteria for PD (n=57) completed baseline assessment and 12 months follow-up. Patients were administered the Panic Agoraphobic Spectrum Self-Report (PAS-SR, Lifetime and Last-Month Versions), and the Panic Disorder Severity Scale (PDSS). We examined patients who met the following criteria at baseline: 1) PDSS total score>7; 2) no current Axis I comorbidity with major depression; 3) no lifetime or current bipolar disorder. All patients were treated with evidence-based psychopharmacological treatment for panic disorder during the 12-month observation period.

RESULTS

Twenty eight patients (48.1%) achieved remission during the follow-up period. In a logistic regression model, controlling for baseline severity, gender and age, only the last-month PAS-SR 'separation anxiety' factor was associated with a lower likelihood of remission.

CONCLUSIONS

Signs and symptoms of separation anxiety in adulthood, as assessed with the PAS-SR Last Month version, are predictors of poor treatment outcome in patients with PD. We submit that the assessment of panic-agoraphobic spectrum features, including adult separation anxiety, should become routine of clinical assessment of patients with PD. It is likely that a better psychopathological characterization of patients may inform treatment selection, and result in better treatment outcome.

Region specific gene expression profile in mouse brain after chronic corticotropin releasing factor receptor 1 activation: the novel role for diazepam binding inhibitor in contextual fear conditioning

We have previously reported that repeated central administration of sub-anxiogenic doses of the corticotropin releasing factor 1 (CRF(1)) agonist Cortagine, termed "priming," elicits a phenotype of increased anxiety-like behaviors in the elevated plus maze (EPM) and open-field test, and enhanced retention of contextual conditioned fear in C57BL/6J mice. Observed behavioral changes were functionally coupled to CRF(1)-mediated elevated central cholecystokinin (CCK) tone in discrete brain regions. However, the changes in gene expression that mediated "priming"-induced behavioral and concurrent molecular changes in specific brain regions remained unknown. In the present study, a complementary DNA microarray analysis was used to investigate gene expression profiles in the hippocampus and prefrontal cortex (PFC) of C57BL/6J mice following the "priming" procedure. Here, we report that chronic stimulation of CRF(1), by i.c.v. administration of 10 ng Cortagine for five days, brought about alterations in the expression of a wide range of hippocampal (31 genes) and PFC (18 genes) genes, implicated in anxiety and aversive memory formation. These expression changes involved genes associated with signal transduction, neurotransmitter secretion, synaptic transmission, myelination, and others involved in the transport, biosynthesis, and binding of proteins. In particular, several genes of the protein kinase A (PKA) and protein kinase C (PKC) signaling cascades, known to be involved in synaptic plasticity, such as neurogranin, calmodulin 3, and the PKA regulatory subunit 1 b were found to be upregulated in the PFC and hippocampus of CRF(1) agonist "primed" mice. Moreover, we show pharmacologically that one of the newly implicated memory regulatory elements, diazepam-binding inhibitor (DBI) is functionally involved in hippocampus-dependent enhancement of contextual fear, a cardinal phenotypic feature of the "primed" mice. Finally, an interaction network mapping of the altered genes and their known interacting partners identified additional molecular candidates responsible for CRF(1)-mediated hypersensitive fear circuitry.

A twin study of the common vulnerability between heightened sensitivity to hypercapnia and panic disorder

For unknown reasons the inhalation of CO(2)-enriched air mixtures evokes acute panic-like symptoms in people with panic disorder and in their unaffected relatives. This study was set to determine whether, and to what extent, CO(2)-induced acute anxiety and panic disorder share the same genetic and environmental determinants. Cholesky structural equation models were used to decompose into genetic and environmental elements the correlation between self-assessed anxiety post-35%CO(2)-65%O(2) inhalation and interview-based DSM-IV lifetime diagnoses of panic disorder in 346 young adult twin pairs of the Norwegian Institute of Health Panel, 12% of whom had been invited to take part into the CO(2) study on the basis of self-reported symptoms of anxiety gathered 4-7 years before the provocation challenge. A full model corrected for the partially selective ascertainment showed that the phenotypic correlation between post-CO(2) anxiety and DSM-IV panic was largely due to additive genetic influences, while shared and unique environmental agents concurred to explain a relatively minor proportion of the correlation between these two traits. According to the best-fitting model the genetic correlation between post-CO(2) anxiety and panic was 0.81 (0.50-0.98); a common genetic factor was sufficient to explain the traits' covariation and a further, specific genetic factor was necessary to account for the residual phenotypic variance. The genetic determinants that lead to overreact to a hypercapnic stimulus coincide at a considerable extent with those that influence liability to naturally occurring panic. Environmental factors provide a modest--or no--contribution to the covariation of CO(2)-provoked anxiety with naturally occurring panic.

Anxiety sensitivity and modulation of the serotonergic system in patients with PD

Anxiety sensitivity, i.e., the fear of anxiety-related bodily sensations, is one of the most studied cognitive variables in panic disorder (PD). However, the effects of selective serotonergic antipanic agents on this variable have not yet been investigated. The present study examines the effects of 6 weeks of treatment with citalopram on anxiety sensitivity in patients with PD. Twenty patients entered the study. On day 0, before starting drug treatment, after 1 week and after 6 weeks of treatment, each patient was evaluated with the Anxiety Sensitivity Index (ASI); the severity of clinical symptomatology was assessed with standardized psychometric scales. Results showed a significant reduction of anxiety sensitivity after 6 weeks of treatment. There was a significant correlation between decrease of anxiety sensitivity and anticipatory anxiety, while no correlations were found between panic attacks and agoraphobic avoidance. These results suggest that antipanic drug treatment decreases anxiety sensitivity.

Sympathetic reactivity in agoraphobic patients with and without personality disorders

OBJECTIVE

To compare sympathetic activity in agoraphobic patients with and without personality disorders before and after 11 weeks inpatient treatment.

METHODS

Agoraphobic patients (n=38), 84% with panic disorder and 47% with personality disorders underwent cold pressure test (CPT), mental stress test (MST), and a specific anxiety test (SAT). Psychological assessments were done by the Bodily Sensations Questionnaire (BSQ), the Agoraphobic Cognitions Questionnaire (ACQ), Spielberger STAI-1 and -2, and a Stress Test Anxiety (STA) questionnaire. Sympathetic activity was measured by blood pressure, heart rate, epinephrine, and norepinephrine.

RESULTS

The sympathetic activity did not differ significantly between patient groups, and the reactivity to stress was very low. The sympathetic reactivity remained unchanged after treatment, whereas psychiatric symptoms decreased. Correlations between sympathetic activity and psychological distress were not significant.

CONCLUSION

Interpretation of bodily signals seems to be more important than the actual sympathetic activity in agoraphobic patients.

Beyond the usual suspects: a cholinergic route for panic attacks

For unknown reasons and through poorly understood mechanisms, people at risk of panic attacks are hypersensitive to suffocative stimuli and experience hyperventilation and anxiety after exposure to heightened concentrations of carbon dioxide. Similarly to the physiological reflex response to hypercapnia in animals and man, the anxious response to carbon dioxide in people with panic disorder is at least partially controlled by the central muscarinic receptors. It is suggested here that some modifications of the cholinergic functions could underlie human individual differences in carbon dioxide sensitivity and proneness to experience panic attacks. The hypothesis is based upon experimental evidence that stressful and potentially harmful stimuli prime relatively long-lasting changes in cholinergic genes expression and cholinergic receptors' regulation. The adaptive sequels of these modifications include protection of the brain from overstimulation, and, at the level of the corticolimbic circuitries, promotion of passive avoidance and learning after stress. The extension of the same modifications to the cholinergic receptors involved in chemoception, however, could lower the threshold for reaction to suffocative stimuli, including carbon dioxide. The exaggerated sensitivity to carbon dioxide observed in humans suffering from panic attacks could then be thought of as an evolutionary cost of the involvement of the cholinergic system in shaping otherwise adaptive responses to stress and threatening stimuli.

Differentiating primary pathophysiologic from secondary adaptational processes

The following manuscript is mainly conceptual in nature. It should be read with reservation since the relevance of its suggestions have yet to be proven. Basically it proposes two rules for the differentiation between primary illness-related pathophysiological vs. secondary adaptational processes. These rules may guide hypotheses generation for further research that is aimed at understanding psychiatric disorders and their shared and unshared mechanisms. For example, in the case of anxiety disorders and depression, it may be of interest to learn if their shared properties are of primary pathophysiological or secondary adaptational significance. We first present some historical observations on the development of the concept of "secondary adaptational processes." We assume such adaptational processes are generated by the organism in order to compensate for primary pathophysiological malfunction or impairment. Next, we propose rules that may enable the dissection of secondary adaptational from primary pathophysiological processes. We also discuss the possible implications of designing studies to sort out these processes, suggesting that the understanding of adaptational processes, may explain the effects of "placebo treatment." Finally we illustrate the application of these rules by two examples: a) amygdala activation, a biological alteration shared by anxiety disorders and major depression and b) elevated plasma soluble interleukin 2 receptor, an unshared property by anxiety disorders and major depression. Also, the first example relates to a biological perturbation associated with a primary pathophysiological mechanism, while the second represents a biological alteration associated with secondary adaptational processes.