A double-blind crossover comparison of clomipramine and desipramine in the treatment of panic disorder

Pharmacotherapy for Anxiety Disorders: From First-Line Options to Treatment Resistance

In this review, the author examines the evidence for psychopharmacologic treatments among adults for generalized anxiety disorder, panic disorder, and social anxiety disorder derived from clinical trials. For each disorder, major categories of drugs are reviewed, and then the evidence-based medications in each category are discussed. The author reviews key safety and tolerability considerations for each of the medications or classes. Evidence-based dosing for most specific agents is displayed in a comprehensive reference table. Subsequently, the author synthesizes the available information to suggest a pragmatic stepwise approach to treatment that accounts for patient-specific factors. To inform the guidance, the author incorporates and refines perspectives from treatment guidelines already written by clinical professional organizations. The author also briefly reviews the relatively new quantitative systematic review methodology of network meta-analysis (NMA) and discusses how NMA may help guide pharmacologic treatment sequencing decisions in the future by way of ranking treatments according to effect size and the relative amount of study to which treatments have been subject. Caveats of NMA studies are briefly discussed, as are results of recent NMAs regarding the pharmacologic treatment of anxiety disorders.

Antidepressants and benzodiazepines for panic disorder in adults

BACKGROUND

A panic attack is a discrete period of fear or anxiety that has a rapid onset, reaches a peak within 10 minutes and in which at least four of 13 characteristic symptoms are experienced, including racing heart, chest pain, sweating, shaking, dizziness, flushing, stomach churning, faintness and breathlessness. Panic disorder is common in the general population with a lifetime prevalence of 1% to 4%. The treatment of panic disorder includes psychological and pharmacological interventions. Amongst pharmacological agents, antidepressants and benzodiazepines are the mainstay of treatment for panic disorder. Different classes of antidepressants have been compared; and the British Association for Psychopharmacology, and National Institute for Health and Care Excellence (NICE) consider antidepressants (mainly selective serotonin reuptake inhibitors (SSRIs)) as the first-line treatment for panic disorder, due to their more favourable adverse effect profile over monoamine oxidase inhibitors (MAOIs) and tricyclic antidepressants (TCAs). In addition to antidepressants, benzodiazepines are widely prescribed for the treatment of panic disorder.

OBJECTIVES

To assess the evidence for the effects of antidepressants and benzodiazepines for panic disorder in adults.

SEARCH METHODS

The Specialised Register of the Cochrane Common Mental Disorders Group (CCMDCTR) to 11 September 2015. This register includes relevant randomised controlled trials from the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE (1950-), Embase (1974-) and PsycINFO (1967-). Reference lists of relevant papers and previous systematic reviews were handsearched. We contacted experts in this field for supplemental data.

SELECTION CRITERIA

All double-blind randomised controlled trials allocating adult patients with panic disorder to antidepressants or benzodiazepines versus any other active treatment with antidepressants or benzodiazepines.

DATA COLLECTION AND ANALYSIS

Two review authors independently checked eligibility and extracted data using a standard form. Data were entered in RevMan 5.3 using a double-check procedure. Information extracted included study characteristics, participant characteristics, intervention details, settings and outcome measures in terms of efficacy, acceptability and tolerability.

MAIN RESULTS

Thirty-five studies, including 6785 participants overall (of which 5365 in the arms of interest (antidepressant and benzodiazepines as monotherapy)) were included in this review; however, since studies addressed many different comparisons, only a few trials provided data for primary outcomes. We found low-quality evidence suggesting no difference between antidepressants and benzodiazepines in terms of response rate (risk ratio (RR) 0.99, 95% confidence interval (CI) 0.67 to 1.47; participants = 215; studies = 2). Very low-quality evidence suggested a benefit for benzodiazepines compared to antidepressants in terms of dropouts due to any cause, even if confidence interval (CI) ranges from almost no difference to benefit with benzodiazepines (RR 1.64, 95% CI 1.03 to 2.63; participants = 1449; studies = 7). We found some evidence suggesting that serotonin reuptake inhibitors (SSRIs) are better tolerated than TCAs (when looking at the number of patients experiencing adverse effects). We failed to find clinically significant differences between individual benzodiazepines. The majority of studies did not report details on random sequence generation and allocation concealment; similarly, no details were provided about strategies to ensure blinding. The study protocol was not available for almost all studies so it is difficult to make a judgment on the possibility of outcome reporting bias. Information on adverse effects was very limited.

AUTHORS' CONCLUSIONS

The identified studies are not sufficient to comprehensively address the objectives of the present review. The majority of studies enrolled a small number of participants and did not provide data for all the outcomes specified in the protocol. For these reasons most of the analyses were underpowered and this limits the overall completeness of evidence. In general, based on the results of the current review, the possible role of antidepressants and benzodiazepines should be assessed by the clinician on an individual basis. The choice of which antidepressant and/or benzodiazepine is prescribed can not be made on the basis of this review only, and should be based on evidence of antidepressants and benzodiazepines efficacy and tolerability, including data from placebo-controlled studies, as a whole. Data on long-term tolerability issues associated with antidepressants and benzodiazepines exposure should also be carefully considered.The present review highlights the need for further higher-quality studies comparing antidepressants with benzodiazepines, which should be conducted with high-methodological standards and including pragmatic outcome measures to provide clinicians with useful and practical data. Data from the present review will be included in a network meta-analysis of psychopharmacological treatment in panic disorder, which will hopefully provide further useful information on this issue.

The noradrenergic paradox: implications in the management of depression and anxiety

Both major depressive disorder and the anxiety disorders are major causes of disability and markedly contribute to a significant global burden of the disease worldwide. In part because of the significant socioeconomic burden associated with these disorders, theories have been developed to specifically build clinical treatment approaches. One such theory, the monoaminergic hypothesis, has led to the development of several generations of selective and nonselective inhibitors of transporters of serotonin and norepinephrine, with the goal of augmenting monoaminergic transmission. These efforts have led to considerable success in the development of antidepressant therapeutics. However, there is a strong correlation between enhanced noradrenergic activity and fear and anxiety. Consequently, some physicians have expressed concerns that the same enhanced noradrenergic activity that alleviates depression could also promote anxiety. The fact that the serotonergic and noradrenergic reuptake inhibitors are successfully used in the treatment of anxiety and panic disorders seems paradoxical. This review was undertaken to determine if any clinical evidence exists to show that serotonergic and noradrenergic reuptake inhibitors can cause anxiety. The PubMed, EMBASE, and Cochrane Library databases were searched, and the results limited to randomized, double-blind, placebo-controlled studies performed in nongeriatric adults and with clear outcome measures were reported. Based on these criteria, a total of 52 studies were examined. Patients in these studies suffered from depression or anxiety disorders (generalized and social anxiety disorders, panic disorder, and posttraumatic stress disorder). The large majority of these studies employed venlafaxine or duloxetine, and the remainder used tri-cyclic antidepressants, atomoxetine, or reboxetine. All the studies reported clinically significant alleviation of depressive and/or anxious symptoms by these therapeutics. In none of these studies was anxiety a treatment-emergent adverse effect. This review argues against the impression that enhanced generalized noradrenergic activity promotes the emergence of anxiety.

BDNF-TRKB signaling system of the dorsal periaqueductal gray matter is implicated in the panicolytic-like effect of antidepressant drugs

A wealth of evidence implicates the BDNF-TRKB system in the therapeutic effects of antidepressant drugs (ADs) on mood disorders. However, little is known about the involvement of this system in the panicolytic property also exerted by these compounds. In the present study we evaluated the participation of the BDNF-TRKB system of the dorsal periaqueductal gray matter (DPAG), a core structure involved in the pathophysiology of panic disorder, in AD-induced panicolytic-like effects in rats. The results showed that short- (3 days) or long-term (21 days) systemic treatment with the tricyclic ADs imipramine, clomipramine or desipramine increased BDNF levels in the DPAG. Only longterm treatment with the selective serotonin reuptake inhibitor fluoxetine was able to increase BDNF levels in this structure. After 21-day treatment, fluoxetine and the three tricyclic ADs used also increased BDNF concentration in the hippocampus, a key area implicated in their mood-related actions. Neither in the DPAG nor hippocampus did long-term treatment with the standard anxiolytics diazepam, clonazepam or buspirone affect BDNF levels. Imipramine, both after short and long-term administration, and fluoxetine under the latter regimen, raised the levels of phosphorylated TRKB in the DPAG. Short-term treatment with imipramine or BDNF microinjection inhibited escape expression in rats exposed to the elevated T maze, considered as a panicolytic-like effect. This anti-escape effect was attenuated by the intra-DPAG administration of the TRK receptor antagonist k252a. Altogether, our data suggests that facilitation of the BDNF-TRKB system in the DPAG is implicated in the panicolytic effect of ADs.

Basing psychiatric classification on scientific foundation: problems and prospects

To examine whether and how the classification of mental disorders can be based on research, we evaluate the relevance of psychiatric science to the major questions in classification. We conclude that most studies cannot inform the validity of diagnostic categories because they are constrained by the classification through a top-down diagnostic approach. Analyses of relationships between diagnostic categories suggest that most interdiagnostic boundaries in current classifications lack validity. Likewise, genetic studies show that the susceptibility to mental illness is at most partly disorder-specific. Neuroimaging research is uninformative due to unsystematic single-diagnosis studies, use of super-healthy controls, and publication bias. Treatment research suggests moderate specificity in several areas of psychopathology (e.g. lithium for bipolar disorder), but lack of specificity is the rule (e.g. the broad indications of serotonin-reuptake inhibitors). In summary, evidence from multiple lines of research converges to indicate that current classifications contain excessively large numbers of categories of limited validity. Dimensional classification will not solve the problem because the number of dimensions is as uncertain as the number of categories. Psychiatric research should discard the assumption that current classification is valid. Instead of diagnosis-specific investigations, studies of unselected groups assessed with bottom-up approaches are needed to advance psychiatry.

Diagnosis and treatment of agoraphobia with panic disorder

Agoraphobia with panic disorder is a phobic-anxious syndrome where patients avoid situations or places in which they fear being embarrassed, or being unable to escape or get help if a panic attack occurs. During the last half-century, agoraphobia has been thought of as being closely linked to the recurring panic attack syndrome, so much so that in most cases it appears to be the typical development or complication of panic disorder. Despite the high prevalence of agoraphobia with panic disorder in patients in primary-care settings, the condition is frequently under-recognised and under-treated by medical providers. Antidepressants have been demonstrated to be effective in preventing panic attacks, and in improving anticipatory anxiety and avoidance behaviour. These drugs are also effective in the treatment of the frequently coexisting depressive symptomatology. Among antidepressant agents, SSRIs are generally well tolerated and effective for both anxious and depressive symptomatology, and these compounds should be considered the first choice for short-, medium- and long-term pharmacological treatment of agoraphobia with panic disorder. The few comparative studies conducted to date with various SSRIs reported no significant differences in terms of efficacy; however, the SSRIs that are less liable to produce withdrawal symptoms after abrupt discontinuation should be considered the treatments of first choice for long-term prophylaxis. Venlafaxine is not sufficiently studied in the long-term treatment of panic disorder, while TCAs may be considered as a second choice of treatment when patients do not seem to respond to or tolerate SSRIs. High-potency benzodiazepines have been shown to display a rapid onset of anti-anxiety effect, having beneficial effects during the first few days of treatment, and are therefore useful options for short-term treatment; however, these drugs are not first-choice medications in the medium and long term because of the frequent development of tolerance and dependence phenomena. Cognitive-behavioural therapy is the best studied non-pharmacological approach and can be applied to many patients, depending on its availability.

A randomized controlled trial of venlafaxine ER and paroxetine in the treatment of outpatients with panic disorder

RATIONALE

Few randomized, placebo-controlled trials have evaluated the comparative efficacy and tolerability of more than one pharmacological agent for panic disorder.

OBJECTIVES

The primary objective of this study was to compare the efficacy and tolerability of venlafaxine extended release (ER) with placebo in treating panic disorder. Secondary objectives included comparing paroxetine with venlafaxine ER and placebo.

METHODS

Outpatients aged > or =18 years (placebo, n = 157; venlafaxine ER 75 mg, n = 156; venlafaxine ER 225 mg, n = 160; paroxetine, n = 151), with a primary diagnosis of panic disorder (+/-agoraphobia) based on the Diagnostic and Statistical Manual of Mental Disorders (Fourth Edition) criteria for > or =3 months were randomly assigned to receive venlafaxine ER (titrated to 75 mg/day or 225 mg/day), paroxetine (titrated to 40 mg/day), or placebo for 12 weeks. The primary efficacy measure was the percentage of patients free of full-symptom panic attacks (> or = four symptoms) at endpoint. Key secondary outcomes included the Panic Disorder Severity Scale (PDSS) mean score change and response.

RESULTS

At endpoint, all active treatment groups showed a significantly (P < 0.01) greater proportion of patients free of full-symptom panic attacks, compared with placebo, and were superior (P < 0.05) on most secondary measures. The venlafaxine ER 225 mg group had significantly (P < 0.05) greater mean PDSS score improvement than the paroxetine group (-12.58 vs -11.87) and a significantly higher proportion of patients free of full symptom panic attacks (70.0 vs 58.3%). Both drugs were generally well tolerated.

CONCLUSION

Venlafaxine ER 75 mg/days and 225 mg/days and paroxetine 40 mg/day were both well tolerated and effective for short-term treatment of panic disorder.

The efficacy of milnacipran in panic disorder: an open trial

The aim of this study is to evaluate the efficacy of milnacipran in the acute treatment of patients with panic disorder. Thirty-one patients who met Diagnostic and statistical manual of mental disorders-IV criteria for panic disorder with or without agoraphobia were included in the study. Patients were initially treated with milnacipran 25 mg twice daily and then 50 mg twice daily until the 10th week. The treatment outcome and panic disorder severity were determined by the Panic Disorder Severity Scale, Panic Inventory, Clinical Global Impression and Hamilton Anxiety Scale, all of which were applied during every evaluation interview. Quality of life (WHOQOL-bref) was evaluated at baseline and at the end of the study. Missing data were handled by using the last observation carried forward for all participants who had taken at least one dose of study medication. Intention-to-treat was used in the analyses. Pharmacological treatment resulted in a clinically and statistically significant mean reduction in all severity measures. Remission (Clinical Global Impression < or = 2) was obtained in 58.1% of the sample. Regarding WHOQOL, we found a significant improvement (P<0.05) across treatment in all the domains studied. Although results may be influenced by the open design of this pilot study and by the small sample size, our findings suggest that milnacipran may be effective for the treatment of panic disorder and justify further research.

Noradrenergic facilitation of shock-probe defensive burying in lateral septum of rats, and modulation by chronic treatment with desipramine

We have previously shown that acute stress-induced release of norepinephrine (NE) facilitates anxiety-like behavioral responses to stress, such as reduction in open-arm exploration on the elevated-plus maze and in social behavior on the social interaction test. Since these responses represent inhibition of ongoing behavior, it is important to also address whether NE facilitates a response that represents an activation of behavior. Correspondingly, it is unknown how a chronic elevation in tonic steady-state noradrenergic (NA) neurotransmission induced by NE reuptake blockade might alter this acute modulatory function, a regulatory process that may be pertinent to the anxiolytic effects of NE reuptake blockers such as desipramine (DMI). Therefore, in this study, we investigated noradrenergic modulation of the shock-probe defensive burying response in the lateral septum (LS). In experiment 1, shock-probe exposure induced an acute 3-fold increase in NE levels measured in LS of male Sprague-Dawley rats by microdialysis. Shock-probe exposure also induced a modest rise in plasma ACTH, taken as an indicator of perceived stress, that returned to baseline more rapidly in rats that were allowed to bury the probe compared to rats prevented from burying by providing them with minimal bedding, indicating that the active defensive burying behavior is an effective coping strategy that reduces the impact of acute shock probe-induced stress. In experiment 2, blockade of either alpha(1)- or beta-adrenergic receptors in LS by local antagonist microinjection immediately before testing reduced defensive burying and increased immobility. In the next experiment, chronic DMI treatment increased basal extracellular NE levels in LS, and attenuated the acute shock probe-induced increase in NE release in LS relative to baseline. Chronic DMI treatment decreased shock-probe defensive burying behavior in a time-dependent manner, apparent only after 2 weeks or more of drug treatment. Moreover, rats treated chronically with DMI showed no significant rise of plasma ACTH in response to shock-probe exposure. Thus, acute stress-induced release of NE in LS facilitated defensive burying, an active, adaptive behavioral coping response. Chronic treatment with the NE reuptake blocker and antidepressant drug DMI attenuated acute noradrenergic facilitation of the active burying response, and also attenuated the level of perceived stress driving that response. These results suggest that long-term regulation of the acute modulatory function of NE by chronic treatment with reuptake blockers may contribute to the mechanisms by which such drugs exert their anxiolytic effects in the treatment of stress-related psychiatric conditions, including depression and anxiety.

Antidepressant-like effects of the vasopressin V1b receptor antagonist SSR149415 in the Flinders Sensitive Line rat

There is an increased interest in the potential of vasopressin receptor antagonists as antidepressants because of the involvement of vasopressin in stress-related behavioral changes. The present study sought to provide confirmatory evidence for the antidepressant-like effects of the selective vasopressin V1b receptor antagonist SSR149415, which had been previously demonstrated in a variety of animal models. The Flinders Sensitive Line (FSL) rat, a selectively bred animal model of depression, was chronically treated for 14 days with SSR149415 (1, 10, and 30 mg/kg), vehicle, or desipramine (5 mg/kg) as a positive control. Approximately 22-24 h after the last treatment, the rats were exposed to a single 5-min session in a cylinder containing 25 degrees C water and immobility was recorded. A control group of Flinders Resistant Line (FRL) rats was included as a reference group as well as one treated with 10 mg/kg SSR149415. Vehicle-treated FSL rats exhibited much more immobility than the FRL rats, and desipramine-treated FSL rats had much lower scores, as expected. Treatment with SSR149415 reduced immobility in the FSL rats at all doses, but only the higher doses reduced it such that they were no longer different from the FRL rats. In contrast, SSR149415 did not alter the lower immobility of the FRL rats. The social interaction test of anxiety was also examined in the FSL rats, at 20-22 h after the last of the 14 injections. Results showed that the 10 and 30 mg/kg doses of SSR149415 increased the time spent in social interaction in the FSL rats, suggesting anxiolytic effects. These findings confirm the antidepressant-like potential of SSR149415 and suggest that it may also have anxiolytic effects. It is likely that the strategy of testing selective vasopressin V1b receptor antagonists will be fruitful.

Contrasting Fos expression induced by acute reboxetine and fluoxetine in the rat forebrain: neuroanatomical substrates for the antidepressant effect

RATIONALE

Antidepressants preferentially facilitating serotonin seem to be particularly effective for treating the anxiety and aggressive component of the depressive syndrome, whereas those with a noradrenergic profile seem to be more effective in reducing psychomotor retardation, although their overall antidepressant effects are about the same. However, the mechanism of this difference remains unknown.

OBJECTIVES

To investigate the neural substrate for the different therapeutic efficacies of fluoxetine and reboxetine, we examined the regional Fos immunoreactivity (Fos-ir) induced by the two agents.

METHODS

Male Wistar rats (290-330 g) were given a subcutaneous injection of fluoxetine (5 or 10 mg/kg), reboxetine (5 or 10 mg/kg) or saline. Two hours later, rats were perfused through the ascending aorta and their brains were processed for Fos immunohistochemistry. Fos-ir was quantified by counting the number of Fos-ir-positive nuclei in six areas of the forebrain.

RESULTS

The shell of the nucleus accumbens was the only region in which both fluoxetine and reboxetine equally increased Fos-ir expression. Fluoxetine particularly induced Fos-ir in the central nucleus of the amygdala. In contrast, reboxetine induced Fos-ir in the cingulate cortex area 3 and the lateral orbital cortex.

CONCLUSIONS

These results suggest that the shell region may be one possible target for the antidepressant effects of fluoxetine and reboxetine. Furthermore, the difference in their clinical effects may depend on their different target sites of action.

Modulation of hyperreactivity to 35% CO2 after one week of treatment with paroxetine and reboxetine: a double-blind, randomized study

The effects of short treatments (7 days) with paroxetine and with reboxetine on the reactivity to inhalations of 35% carbon dioxide (CO2)/65% oxygen (O2) were compared in 28 patients with Panic Disorder who had positive responses to 35% CO2 inhalations. A double-blind, randomized design was applied. Each patient was given the 35% CO2 challenge on days 0 (before starting the treatment) and 7. Anxiety reactivity to CO2 decreased significantly with both drugs but the decrease was significantly stronger in the group treated with paroxetine. The rate of patients whose reactivity has reduced of at least 50% after 7 days was significantly higher in the group treated with paroxetine (10/14, 71.5%) than in the one treated with reboxetine (3/14, 21.5%). These results indicate that the modulation of the serotonergic system is more relevant for CO2 hyperreactivity than the modulation of the noradrenergic one.

Antidepressant effects of citalopram and CRF receptor antagonist CP-154,526 in a rat model of depression

Due to the interest in the antidepressant potential of nonpeptide corticotropin-releasing factor (CRF)(1) receptor antagonists, the present investigation examined the antidepressant-like effects of the CRF(1) receptor antagonist CP-154,526 on the exaggerated swim test immobility in the Flinders Sensitive Line (FSL) rat, a genetic animal model of depression. Chronic treatment with CP-154,526 (10 mg/kg; 2x day) for 14 days increased swimming in the Flinders Sensitive Line rats. Citalopram (5 and 10 mg/kg; 2x day) and desipramine (5 mg/kg; 1x day) also significantly increased swimming in the Flinders Sensitive Line rats, as expected. However, neither CP-154,526 nor citalopram (10 mg/kg) altered swimming times in the control Flinders Resistant Line (FRL) rats. Citalopram (10 mg/kg) and CP-154,526 also increased the abnormally low level of social interaction behavior in the Flinders Sensitive Line rats. These findings indicate that citalopram and CP154,526, a CRF(1) receptor antagonist, have both antidepressant and anxiolytic effects that can be detected in an experimental model of depression only and not in "normal" control animals.

Paroxetine influences respiration in rats: implications for the treatment of panic disorder

Since hyperventilation and shortness of breath are characteristic features of panic attacks, and since the attacks can be elicited by CO(2) inhalation, an involvement of central or peripheral chemoreceptors in the pathophysiology of panic disorder has been suggested. Prompted by clinical reports suggesting that the susceptibility to spontaneous as well as CO(2)-induced anxiety and hyperventilation is attenuated by serotonin reuptake inhibitors (SRIs), we undertook the present study in order to explore the possible effect of an SRI, paroxetine, on baseline respiration and CO(2)-induced hyperventilation in freely moving Wistar rats. A significant increase in baseline respiratory rate was seen both after 5 and 15 weeks of treatment with paroxetine. CO(2) exposure induced a dose-dependent increase in respiratory rate, but not tidal volume, in both paroxetine-treated rats and controls; this response was reduced after 15 weeks of paroxetine treatment, but not after 5 weeks of treatment. We suggest that an influence on the regulation of respiration may be of importance for the anti-panic effect of SRIs.

Reboxetine and citalopram in panic disorder: a single-blind, cross-over, flexible-dose pilot study

Both noradrenergic and serotonergic systems have been implicated in the pathophysiology of panic disorder. The advent of selective serotonin (5-HT) reuptake inhibitors (SSRIs) (e.g. citalopram) and, more recently, selective noradrenergic (NA) reuptake inhibitors (NRIs) (e.g. reboxetine) has provided potentially important avenues of treatment for the disorder. To date, the comparative efficacy of selective NA and 5-HT reuptake inhibitors for panic disorder remains unresolved. Nineteen patients with panic disorder were randomized in a single-blind, cross-over design to either citalopram or reboxetine for 8 weeks and after a 2-week washout were switched to the other study drug. At week 18, seven of 13 patients (54%) in the intent-to-treat sample responded to reboxetine and nine of 11 patients responded to citalopram (82%). Both citalopram and reboxetine led to significant improvements in panic attack severity with no apparent between-drug differences in efficacy. However, citalopram demonstrated superior efficacy in treating depressive symptoms. One non-responder to citalopram responded to reboxetine and three non-responders to reboxetine responded to citalopram. Although SSRIs are viewed as a first-line treatment for panic disorder, these results suggest that a NA agent such as reboxetine may also have a role. These data also suggest an advantage for citalopram in treating comorbid depressive symptoms, although some patients may respond preferentially to an SSRI and other patients to an NRI.

The neurobiology and control of anxious states

Fear is an adaptive component of the acute "stress" response to potentially-dangerous (external and internal) stimuli which threaten to perturb homeostasis. However, when disproportional in intensity, chronic and/or irreversible, or not associated with any genuine risk, it may be symptomatic of a debilitating anxious state: for example, social phobia, panic attacks or generalized anxiety disorder. In view of the importance of guaranteeing an appropriate emotional response to aversive events, it is not surprising that a diversity of mechanisms are involved in the induction and inhibition of anxious states. Apart from conventional neurotransmitters, such as monoamines, gamma-amino-butyric acid (GABA) and glutamate, many other modulators have been implicated, including: adenosine, cannabinoids, numerous neuropeptides, hormones, neurotrophins, cytokines and several cellular mediators. Accordingly, though benzodiazepines (which reinforce transmission at GABA(A) receptors), serotonin (5-HT)(1A) receptor agonists and 5-HT reuptake inhibitors are currently the principle drugs employed in the management of anxiety disorders, there is considerable scope for the development of alternative therapies. In addition to cellular, anatomical and neurochemical strategies, behavioral models are indispensable for the characterization of anxious states and their modulation. Amongst diverse paradigms, conflict procedures--in which subjects experience opposing impulses of desire and fear--are of especial conceptual and therapeutic pertinence. For example, in the Vogel Conflict Test (VCT), the ability of drugs to release punishment-suppressed drinking behavior is evaluated. In reviewing the neurobiology of anxious states, the present article focuses in particular upon: the multifarious and complex roles of individual modulators, often as a function of the specific receptor type and neuronal substrate involved in their actions; novel targets for the management of anxiety disorders; the influence of neurotransmitters and other agents upon performance in the VCT; data acquired from complementary pharmacological and genetic strategies and, finally, several open questions likely to orientate future experimental- and clinical-research. In view of the recent proliferation of mechanisms implicated in the pathogenesis, modulation and, potentially, treatment of anxiety disorders, this is an opportune moment to survey their functional and pathophysiological significance, and to assess their influence upon performance in the VCT and other models of potential anxiolytic properties.

Association between estrus cycle-related changes in respiration and estrus cycle-related aggression in outbred female Wistar rats

Premenstrual dysphoric disorder is characterized by irritability surfacing during the luteal phase of the menstrual cycle, and disappearing shortly after the onset of menstruation. Although the cardinal symptoms of premenstrual dysphoria are different from those of panic disorder, the two conditions share a number of traits indicating that they both may be associated with abnormalities in the regulation of respiration. Both subjects with panic disorder and subjects with premenstrual dysphoria are hence reported to display enhanced respiratory variability, and to experience anxiety when exposed to CO(2). In the present study, the possible influence of the estrus cycle on respiratory parameters in outbred female rats of the Wistar strain was investigated. Before being tested with respect to respiration, the rats were subdivided into two groups: those displaying estrus cycle-related variation in aggression, as evaluated using the resident intruder paradigm, and those not showing aggression throughout the cycle. Whereas the former group was found to display higher respiratory rate during the diestrus phase than during the proestrus/estrus phase, no cycle-related variation in respiration was observed in animals not showing cycle-related variation in aggression. The results support previous studies indicating that the estrus cycle exerts an influence on respiration, and suggest that rats prone to cycle-related aggression are more sensitive also to the influence of hormonal cyclicity on respiration. The possible bearing of these findings for the aberration in respiration displayed by subjects with premenstrual dysphoria is discussed.

Depression as a spreading adjustment disorder of monoaminergic neurons: a case for primary implication of the locus coeruleus

A model for the pathophysiology of depression is discussed in the context of other existing theories. The classic monoamine theory of depression suggests that a deficit in monoamine neurotransmitters in the synaptic cleft is the primary cause of depression. More recent elaborations of the classic theory also implicitly include this postulate, other theories of depression frequently prefer to depart from the monoamine-based model altogether. We suggest that the primary defect emerges in the regulation of firing rates in brainstem monoaminergic neurons, which brings about a decrease in the tonic release of neurotransmitters in their projection areas, an increase in postsynaptic sensitivity, and concomitantly, exaggerated responses to acute increases in the presynaptic firing rate and transmitter release. It is proposed that the initial defect involves, in particular, the noradrenergic innervation from the locus coeruleus (LC). Dysregulation of the LC projection activities may lead in turn to dysregulation of serotonergic and dopaminergic neurotransmission. Failure of the LC function could explain the basic impairments in the processing of novel information, intensive processing of irrational beliefs, and anxiety. Concomitant impairments in the serotonergic neurotransmission may contribute to the mood changes and reduction in the mesotelencephalic dopaminergic activity to loss of motivation, and anhedonia. Dysregulation of CRF and other neuropeptides such as neuropeptide Y, galanin and substance P may reinforce the LC dysfunction and thus further weaken the adaptivity to stressful stimuli.

Exposure to violence and its relationship to psychopathology in adolescents

OBJECTIVES

This study aimed to establish prevalence of adolescents' exposure to violence and related symptoms in the South African context and to explore relationships between exposure and symptoms.

SETTING

Four high schools in Cape Town, South Africa.

METHODS

Self report questionnaires were administered to 104 students. Types of violence explored included: witnessing or being a victim of violence perpetrated by someone known to the child or in the home and witnessing or being a victim of violence perpetrated by a stranger. The Harvard Trauma Scale, Beck Depression Inventory, and Zung Self-Rating Anxiety Scale were used to assess potentially related symptoms.

RESULTS

The majority of children had been exposed to at least one type of violence, and exposure to the one type of violence was related to the other type. Symptoms of post-traumatic stress disorder and depression appear to be related to most types of exposure to violence, but anxiety symptoms only to exposure to violence perpetrated by someone known to the child or in the home.

CONCLUSIONS

Rates of exposure to violence, and related symptoms, were unacceptably high. Symptoms were associated with exposure to violence.

Panic disorder

In this article, the authors review the most recent advances in the pharmacotherapy, psychotherapy, and combined therapy for panic disorder. The authors focus on peer-reviewed data and on pragmatic clinical approaches that may help patients suffering from panic disorder.

Effects of the CRF(1) receptor antagonist, CP 154,526, in the separation-induced vocalization anxiolytic test in rat pups

CRF(1) receptor antagonists have been proposed as novel pharmacological treatments for depression, anxiety and stress disorders. The primary goal of the present study was to evaluate the effects of the CRF(1) receptor antagonist, CP 154,526, in the separation-induced vocalization (SIV) model of anxiety. Nine- to 11-day-old rat pups were separated from their litter and the effects of intraperitoneally administered test compounds on the elicited ultrasonic vocalizations were measured. Side-effect potential was assessed using a modified inclined plane test ('time on an inclined plane', or TIP), and using negative geotaxis. SIV was reduced by CP 154,526 at doses that did not affect TIP or negative geotaxis, a profile like that of the 5-HT(1A) partial agonist buspirone. The benzodiazepine anxiolytic, diazepam, decreased SIV but also produced significant side effects at one to three-fold higher doses. Additional pharmacological characterization of SIV demonstrated anxiolytic-like effects of the atypical antipsychotic, clozapine, but not the typical antipsychotic, haloperidol, and of the serotonin reuptake inhibitor, zimelidine, but not the norepinephrine reuptake inhibitor, desipramine. In summary, the data support the conclusion that selective CRF(1) receptor antagonists may have utility in anxiety and stress disorders. The data further support the use of separation-induced vocalizations for identifying mechanistically diverse compounds with anxiolytic actions in man.