The neurochemistry of anxiety: an update

Development and persistence of neuropathic pain through microglial activation and KCC2 decreasing after mouse tibial nerve injury

Gamma-amino butyric acid (GABA) is an inhibitory neurotransmitter in the mature brain, but is excitatory during development and after motor nerve injury. This difference in GABAergic action depends on the intracellular chloride ion concentration ([Cl-]i), primarily regulated by potassium chloride co-transporter 2 (KCC2). To reveal precise processes of the neuropathic pain through changes in GABAergic action, we prepared tibial nerve ligation and severance models using male mice, and examined temporal relationships amongst changes in (1) the mechanical withdrawal threshold in the sural nerve area, (2) localization of the molecules involved in GABAergic transmission and its upstream signaling in the dorsal horn, and (3) histology of the tibial nerve. In the ligation model, tibial nerve degeneration disappeared by day 56, but mechanical allodynia, reduced KCC2 localization, and increased microglia density remained until day 90. Microglia density was higher in the tibial zone than the sural zone before day 21, but this result was inverted after day 28. In contrast, in the severance model, all above changes were detected until day 28, but were simultaneously and significantly recovered by day 90. These results suggested that in male mice, allodynia may be caused by reduced GABAergic synaptic inhibition, resulting from elevated [Cl-]i after the reduction of KCC2 by activated microglia. Furthermore, our results suggested that factors from degenerating nerve terminals may diffuse into the sural zone, whereby they induced the development of allodynia in the sural nerve area, while other factors in the sural zone may mediate persistent allodynia through the same pathway.

Short- and long-term functional consequences of fluoxetine exposure during adolescence in male rats

BACKGROUND

Fluoxetine (FLX), a selective serotonin reuptake inhibitor, is prescribed for the treatment of major depressive disorder in young populations. Here, we explore the short- and long-term consequences of adolescent exposure to FLX on behavioral reactivity to emotion-eliciting stimuli.

METHODS

Adolescent male rats received FLX (10 mg/kg) twice daily for 15 consecutive days (postnatal days 35-49). The influence of FLX on behavioral reactivity to rewarding and aversive stimuli was assessed 24 hours (short-term) or 3 weeks after FLX treatment (long-term). A separate group of adult rats was also treated with FLX (postnatal days 65-79) and responsiveness to forced swimming was assessed at identical time intervals as with the adolescents.

RESULTS

Fluoxetine exposure during adolescence resulted in long-lasting decreases in behavioral reactivity to forced swimming stress and enhanced sensitivity to sucrose and to anxiety-eliciting situations in adulthood. The FLX-induced anxiety-like behavior was alleviated by re-exposure to FLX in adulthood. Fluoxetine treatment during adolescence also impaired sexual copulatory behaviors in adulthood. Fluoxetine-treated adult rats did not show changes in behavioral reactivity to forced swim stress as observed in those treated during adolescence and tested in adulthood.

CONCLUSIONS

Treating adolescent rats with FLX results in long-lived complex outputs regulated by the emotional valence of the stimulus, the environment in which it is experienced, and the brain circuitry likely being engaged by it. Our findings highlight the need for further research to improve our understanding of the alterations that psychotropic exposure may induce on the developing nervous system and the potential enduring effects resulting from such treatments.

Agoraphobia: a review of the diagnostic classificatory position and criteria

The status of agoraphobia (AG) as an independent diagnostic category is reviewed and preliminary options and recommendations for the fifth edition of The Diagnostic and Statistical Manual (DSM-V) are presented. The review concentrates on epidemiology, psychopathology, neurobiology, vulnerability and risk factors, clinical course and outcome, and correlates and consequences of AG since 1990. Differences and similarities across conventions and criteria of DSM and ICD-10 are considered. Three core questions are addressed. First, what is the evidence for AG as a diagnosis independent of panic disorder? Second, should AG be conceptualized as a subordinate form of panic disorder (PD) as currently stipulated in DSM-IV-TR? Third, is there evidence for modifying or changing the current diagnostic criteria? We come to the conclusion that AG should be conceptualized as an independent disorder with more specific criteria rather than a subordinate, residual form of PD as currently stipulated in DSM-IV-TR. Among other issues, this conclusion was based on psychometric evaluations of the construct, epidemiological investigations which show that AG can exist independently of panic disorder, and the impact of agoraphobic avoidance upon clinical course and outcome. However, evidence from basic and clinic validation studies remains incomplete and partly contradictory. The apparent advantages of a more straightforward, simpler classification without implicit hierarchies and insufficiently supported differential diagnostic considerations, plus the option for improved further research, led to favoring the separate diagnostic criteria for AG as a diagnosis independent of panic disorder.

Antidepressant treatment can normalize adult behavioral deficits induced by early-life exposure to methylphenidate

BACKGROUND

Methylphenidate (MPH) is prescribed for the treatment of attention-deficit/hyperactivity disorder. Exposure to MPH before adulthood causes behavioral deficits later in life, including anxiety- and depression-like behaviors and decreased responding to natural and drug rewards. We examined the ability of fluoxetine (FLX), a selective serotonin reuptake blocker, to normalize these MPH-induced behavioral deficits.

METHODS

Male rats received MPH (2.0 mg/kg) or saline (VEH) during preadolescence (postnatal day [PD] 20-35). When adults, rats were divided into groups receiving no treatment, acute or chronic FLX, and behavioral reactivity to several emotion-eliciting stimuli were assessed.

RESULTS

The MPH-treated rats were significantly less responsive to natural (i.e., sucrose) and drug (i.e., morphine) rewards and more sensitive to stress- and anxiety-eliciting situations. These MPH-induced deficits were reversed by exposure to FLX.

CONCLUSIONS

These results indicate that exposure to MPH during preadolescence leads to behavioral alterations that endure into adulthood and that these behavioral deficits can be normalized by antidepressant treatment. These results highlight the need for further research to better understand the effects of stimulants on the developing nervous system and the potential enduring effects resulting from early-life drug exposure.

The effect of alpha-2 adrenergic agonists on memory and cognitive flexibility

BACKGROUND

The noradrenergic system modulates cognitive flexibility for insight-based problem solving in studies using beta-adrenergic antagonists, which block noradrenergic neurotransmission postsynaptically. However, it is not known whether alpha2-adrenergic agonists, that decrease noradrenergic neurotransmission by presynaptic inhibition, have the same effect.

OBJECTIVES

Therefore, we wished to test whether alpha2-adrenergic agonists would have a similar effect on cognitive flexibility.

METHODS

Eighteen normal adults were tested on cognitive flexibility, problem solving, verbal and spatial memory tasks after receiving clonidine (0.1 mg), an alpha2-agonist, placebo, or ephedrine (25 mg), a noradrenergic stimulant.

RESULTS

Three-way analysis of variance revealed no significant drug effect on cognitive flexibility or problem solving. There was also no significant effect of clonidine on memory.

CONCLUSIONS

Therefore, alpha2-agonists do not influence cognitive flexibility in the same manner as beta-antagonists. Better performance on memory with clonidine might be expected based on primate studies demonstrating benefits in working memory using clonidine. This benefit was not observed for the commonly used clinical memory tasks in our study. This may have implications for why clonidine has not demonstrated efficacy for cognitive disorders such as Alzheimer disease, despite its known benefit for working memory in animal models.

Modulation of anxiety circuits by serotonergic systems

Anxiety is a complex emotional state associated with sustained heightened autonomic and behavioral arousal and an increase in avoidance behavior. Anxiety-related behavior is a form of risk assessment behavior that is associated with a level of uncertainty or unpredictability regarding the outcome of emotionally salient events, often when both rewarding and aversive outcomes are possible. In this review, we highlight recent advances in our understanding of the neural circuits regulating anxiety states and anxiety-related behavior with an emphasis on the role of brainstem serotonergic systems in modulating anxiety-related circuits. In particular, we explore the possibility that the regulation of anxiety states and anxiety-related behavior by serotonergic systems is dependent on a specific, topographically organized mesolimbocortical serotonergic system that originates in the mid-rostrocaudal and caudal parts of the dorsal raphe nucleus.

GABAergic signaling in the developing cerebellum

In the adult central nervous system (CNS), GABA is a predominant inhibitory neurotransmitter that regulates glutamatergic activity. Recent studies have revealed that GABA serves as an excitatory transmitter in the immature CNS and acts as a trophic factor for brain development. Furthermore, synaptic transmission by GABA is also involved in the expression of higher brain functions, such as memory, learning and anxiety. These results indicate that GABA plays various roles in the expression of brain functions and GABAergic roles change developmentally in accordance with alterations in GABAergic transmission and signaling. We have investigated morphologically the developmental changes in the GABAergic transmission system and the key factors important for the formation of GABAergic synapses and networks using the mouse cerebellum, which provides an ideal system for the investigation of brain development. Here, we focus on GABA and GABA(A) receptors in the developing cerebellum and address the processes of how GABA exerts its effect on developing neurons and the mechanisms underlying the formation of functional GABAergic synapses.

Corticotropin-releasing factor and acute stress prolongs serotonergic regulation of GABA transmission in prefrontal cortical pyramidal neurons

The stress-related neuropeptide corticotropin-releasing factor (CRF) and the serotonin system are both critically involved in the pathophysiology of mental disorders, including anxiety and depression. To understand the potential link between them, we investigated the impact of CRF on 5-HT functions in pyramidal neurons of the prefrontal cortex (PFC), a brain region that is crucial for the control of emotion and cognition. One prominent function of serotonin in PFC is to regulate GABAergic inhibitory transmission, as indicated by a 5-HT-induced large, desensitizing (approximately 4 min) enhancement of the amplitude and frequency of spontaneous IPSCs (sIPSCs). In PFC slices exposed to CRF treatment, the regulation of sIPSCs by 5-HT was significantly prolonged (8-10 min), and this effect of CRF was blocked by treatment with the competitive CRF receptor antagonist alpha-helical CRF9-41 and with the CRF-R1-specific antagonist astressin. Inhibiting phospholipase C or protein kinase C (PKC) abolished the prolongation by CRF of the effects of 5-HT on sIPSCs. In PFC slices prepared from animals previously exposed to acute stress (forced swim or elevated platform), the regulation of sIPSCs by 5-HT was significantly prolonged, mimicking the effect of CRF treatment. The stress-induced prolongation of the effects of 5-HT on sIPSCs was diminished by alpha-helical CRF9-41 treatment, mimicked by direct activation of PKC, and reversed by short-term treatment with drugs that have anxiolytic efficacy. These results show that in response to stressful stimuli, CRF alters the serotonergic regulation of GABA transmission through a mechanism that is dependent on PKC. The interaction between CRF and 5-HT may play an important role in psychiatric disorders, in which both are highly implicated.

Normal formation of the postsynaptic elements of GABAergic synapses in the reeler cerebellum

Synaptic transmission mediated by gamma-amino butyric acid (GABA) plays an important role in inhibition of glutamatergic excitatory transmission and expression of higher brain functions, such as memory, learning and anxiety. To elucidate mechanisms underlying formation of the postsynaptic elements for GABAergic transmission, we employed the reeler mutant mice in this study. In the reeler cerebellum, abnormal cytoarchitecture and an aberrant environment affect the formation of neural networks and maturation of neurons. We examined the expression and localization of GABA(A) receptor alpha subunits in the reeler cerebellum and determined whether various abnormalities in the reeler mice affected formation of the postsynaptic elements. In situ hybridization analysis revealed that the specific expression of alpha subunit mRNAs in each neuronal type was preserved. Abnormal expression of alpha subunits was not detected, although GABAergic networks were altered and neuronal maturation was severely disturbed. Immunohistochemistry for the alpha1 and alpha6 subunits, which were expressed abundantly in the reeler cerebellum, revealed that both subunit proteins accumulated at positions adjacent to GABAergic terminals. These results, taken together, suggested that expression of the GABA(A) receptor subunits in postsynaptic neurons might be genetically determined, but trafficking and accumulation of the subunit proteins at the GABAergic synapse may be induced by GABAergic innervation.

The false organic-psychogenic distinction and related problems in the classification of erectile dysfunction

The traditional distinction between organic and psychogenic erectile dysfunction (ED) was maintained in the recent report of the Nomenclature Committee of the International Society for Sexual and Impotence Research. Among the major problems with this distinction are that it is based on an obsolete view of mind-body distinctions, does not take into account knowledge of the neurobiology of 'psychological' disorders, disregards the fundamental meaning of 'psychosomatic,' is too often diagnosed by exclusion, and may imply to the patient that his ED is 'all in the mind.' As a result, the distinction has become counterproductive in the diagnosis, classification, and treatment of ED, and in research into the causes of ED. An alternative taxonomy, based on that proposed by the Nomenclature Committee, reclassifies as organic several of the causes of ED now considered to be psychogenic, and considers others as situational ED, a class reserved for episodic occurrences of ED clearly due to particular attributes of sexual encounters.

Balance control and posture differences in the anxious BALB/cByJ mice compared to the non anxious C57BL/6J mice

A relation between anxiety disorders and balance control dysfunctions has been observed in many studies in humans. A mismatch in the integration of sensory inputs could trigger these disturbances. Very few experimental animal procedures have been designed to study the functional link between anxiety and balance control. A task was therefore developed, challenging the visual, vestibular and somesthesic sensory systems in mice. The test, called the 'rotating beam', gave an accurate assessment of balance control and the posture, using sensitive measures (number of falls and imbalances, position of tail and trunk). Striking differences were observed between the two inbred strains of mice known to have radically different anxiety-related behaviour. The highly anxious strain, BALB/cByJ, performed poorly compared to the non anxious strain, C57BL/6J. Balance control and postural abilities of anxious mice were improved by acute anxiolytic diazepam treatment. Lower behavioural performance level was registered in non anxious mice given anxiogenic beta-CCM treatment. The findings account for a strong relationship between anxiety and balance control in mice. Finally, the highly sensitive procedure proved to be well suited to the study of functional links between anxiety and sensorimotor processes.

The psychobiology of anxiolytic drugs. Part 1: Basic neurobiology

The authors provide an overview of the current state of knowledge with regards to the neurobiological mechanisms involved in normal and pathological anxiety. A brief review of the classification and cognitive psychology of anxiety is followed by a more in-depth look at the neuroanatomical and neurochemical processes and their relevance to our understanding of the modes of action of anxiolytic drugs. The serotonergic, noradrenergic, and gamma-aminobutyric acidergic systems are reviewed. The numerous physiological and pharmacological methods of anxiety provocation and the increasing importance of functional neuroimaging are also examined. The review provides an overview of the biology and basic pharmacology of anxiolytic drugs, and compliments the more clinically oriented companion review.

Season of birth in panic disorder

Several studies have investigated the seasonal distribution of the birth dates of patients with psychiatric diseases. Our purpose was to verify if there is a specific distribution (by month) of birth dates in subjects with panic disorder (PD). The birth dates of 843 outpatients with a diagnosis of PD were compared with those of 1,181 subjects with other mental diseases. The birth dates of psychiatric patients were compared to those of the general Tuscane and Italian populations. The monthly distribution of birth in patients with PD (with and without comorbidity) peaked in September to December, while no relevant deviation in birth rate was observed in other mental diseases. Our results suggest a pathogenic role of birth seasonality in the development of PD.

[3H]Paroxetine binding to human peripheral lymphocyte membranes of patients with major depression before and after treatment with fluoxetine

Serotonin has been involved in major depression and is also related to central and peripheral mechanisms of neuroimmunomodulation. Recently, the uptake of [3H]serotonin into human peripheral blood lymphocytes has been reported. We determined the density of serotonin uptake sites by the binding of [3H]paroxetine to blood peripheral lymphocyte membrane preparations of controls and of patients with major depression before and after treatment with fluoxetine for six weeks. The severity of depression was assessed by the use of Hamilton Rating Scale for Depression and of Beck Depression Inventory. There was a reduction in the number of sites for [3H]paroxetine in patients before administration of the antidepressant respecting controls, and a recovery after the treatment. Affinity was unchanged. No correlation was obtained between the severity of symptoms determined by Hamilton Rating Scale for Depression or by Beck Depression Inventory, and the number of binding sites for [3H]paroxetine. The levels of the plasma serotonin metabolite, 5-hydroxyindoleacetic acid, did not differ between the three groups of subjects, but serotonin was lower in patients after treatment respecting controls and in patients before treatment. The significant correlation between specific binding of [3H]paroxetine and plasma serotonin levels in controls was not present in the patients. Lymphocyte serotonin transporter is decreased in major depressed patients and is modulated by antidepressant treatment. In addition of counting with a peripheral marker in depression, the study of serotonin system in lymphocytes might contribute to understand the bi-directional interaction between the nervous and the immune systems.

Structure and subunit composition of GABA(A) receptors

GABA(A) receptors are the major inhibitory neurotransmitter receptors in the brain and are the site of action of many clinically important drugs. These receptors are composed of five subunits that can belong to eight different subunit classes. If all GABA(A) receptor subunits could randomly combine with each other, an extremely large number of GABA(A) receptor subtypes with distinct subunit composition and arrangement would be formed. Depending on their subunit composition, these receptors would exhibit distinct pharmacological and electrophysiological properties. Recent evidence, however, indicates that not all subunits can assemble efficiently with each other and form functional homo- or hetero-oligomeric receptors. In addition, the efficiency of formation of hetero-oligomeric assembly intermediates determines the subunit stoichiometry and subunit arrangement for each receptor and thus further reduces the possible heterogeneity of GABA(A) receptors in the brain. Studies investigating the subunit composition of native GABA(A) receptors support this conclusion, but also indicate that receptors composed of one, two, three, four, or five different subunits might exist in the brain. Using a recently established immunodepletion technique, the subunit composition and quantitative importance of native GABA(A) receptor subtypes can be determined. This information, together with studies on the regional, cellular and subcellular distribution of these receptor subtypes, will be the basis for a rational development of drugs that specifically affect the GABAergic system.

Serotonin and externalizing behavior in young children

Considerable evidence suggests that there is a relationship between pathologic aggressive behavior and low cerebrospinal fluid (CSF) concentrations of the serotonin metabolite 5-hydroxyindoleacetic acid (5-HIAA) in both humans and non-human primates. The purpose of this investigation is to examine the relationship between CSF concentrations of human newborn 5-HIAA and subsequent aggressive behavior observed at 30 months of age. Leftover portions of culture negative CSF drawn from febrile infants (age, birth to 3 months) were assayed for 5-HIAA. Family environment and child behavior were assessed at 30 months by parent report. Subjects with 5-HIAA levels below the median of the distribution had higher externalizing behavior scores at 30 months than did subjects whose 5-HIAA levels fell above the median (P = 0.02). While it is likely that serotonin mediates one component of genetic liability to antisocial outcome, the magnitude of that component may be less than what has been inferred from previously published reports.

Pain. A prelude

Although pain is a common fear to most, our overall ability to recognize pain, and assess and intervene with appropriate therapies is mediocre at best. However, if made a priority, substantial gains can be made in improving patient satisfaction with pain control and in rectifying deficits in the knowledge of health-care professionals. This goal is not easily obtained and generally requires time, patience, and a multidisciplinary team approach. Pain can induce numerous metabolic and neuroendocrine responses. While seemingly homeostatic, these changes can have significant physiologic and sometimes adverse consequences. Anesthesia and analgesia, especially by way of neural blockade, can alleviate some of the changes and sometimes improve unwanted consequences. While at times these techniques have not significantly altered outcome, at other times significant benefits have been observed. More sophisticated techniques and pharmacotherapies are being developed and introduced with increased frequency, but alone they will probably have only minimal impact on overall morbidity and mortality. The integration of a multimodal approach seems logical in the critical care setting, with analgesia as the cornerstone.

125I-iomazenil binding shows stress- and/or diazepam-induced reductions in mouse brain: supporting data for 123I-iomazenil SPECT study of anxiety disorders

Effects of repeated swim stress on the binding of 125I-iomazenil were examined in the brains of diazepam-treated and non-treated mice. The mice were orally administered diazepam or vehicle (0.5% ethylene glycol) and subjected to daily swim stress (at 20 degrees C for 10 min) for seven consecutive days. The distribution and the amount of 125I-iomazenil binding were analyzed autoradiographically after in vivo and in vitro binding experiments. Repeated swim stress decreased the in vivo binding in the hippocampus (p < 0.05) and cerebral cortex (p < 0.05) of vehicle-treated mice but caused no significant changes in diazepam-treated mice. Subchronic treatment with diazepam decreased the in vivo binding approximately 50% in all brain regions examined (p < 0.01). The in vitro experiment, however, revealed no significant changes except in the hippocampus, where a small but significant decrease in the binding was observed after subchronic treatment with diazepam (p < 0.01). The stress- or diazepam-induced reductions seem to represent alterations in the in vivo environment related to 125I-iomazenil binding. These results suggest that we can investigate the pathophysiology of stress and anxiety with 123I-iomazenil SPECT. Care must be taken concerning the effects of benzodiazepines.

Auditory event-related potentials in panic disorder

To investigate the psychophysiological features of panic disorder (PD), we recorded auditory event-related potentials (ERPs) in 12 patients with PD meeting the DSM-IV criteria and in 12 age-matched normal controls. The ERPs were recorded during a standard two-tone discrimination task (oddball task). The probabilities of the rare target (1200 Hz) and frequent non-target tones (1000 Hz) were 15 and 85%, respectively. The subjects were required to press a button in response to the rare target tones. Scalp electroencephalograms were recorded from Fz, Cz, Pz, C3, and C4. The State-Trait Anxiety Inventory and Manifest Anxiety Scale scores were assessed for clinical evaluation. Analysis of variance revealed that the N1 and N2 amplitudes for target tones and the N1 amplitude for non-target tones were significantly larger in the PD patients than those in the controls. The two groups did not differ significantly in P3 latency and amplitude. The larger N1 and N2 amplitudes in the PD patients are suggestive of alteration of early information processing in PD.

Enlarged frontal P300 to stimulus change in panic disorder

This study investigated event-related potential (ERP) indices of information processing in sufferers of panic disorder (PD). ERPs were recorded from 14 PD patients and 15 controls during an auditory target detection task. The task required subjects to discriminate infrequent target tones (p = .14; 2000 Hz) from frequent (p = .72; 1000 Hz) and infrequent (p = .14; 500 Hz) distractor tones. A frontal P300 (P3a) identified in the PD group was characteristic of activity that would be expected to novel, task-irrelevant stimuli and is consistent with junctional pathology involving the prefrontal-limbic pathways. This study provides psychophysiological evidence of an abnormality in PD of the brain's processing of physical changes in the stimulus field that occurs even under conditions of low stimulus load. It may assist in helping to understand the breakdown in information processing that occurs in PD under high load conditions such as crowds and supermarkets.

Serotonin turnover rate, [3H]paroxetine binding sites, and 5-HT1A receptors in the hippocampus of rats subchronically treated with clonazepam

Selective central benzodiazepine agonists, such as clonazepam, are known to modify serotonin and 5-hydroxyindoleacetic content in the brain. In order to further study the effect of this benzodiazepine on serotonin turnover rate, rats received clonazepam, 10 mg/kg for 10 days, and the concentrations of serotonin and 5-hydroxyindoleacetic acid were determined in the hippocampus after inhibition of monoamineoxidase with pargyline. The results indicate a reduction in the turnover rate of the monoamine. In addition, the systemic administration of clonazepam produced a decrease in the Bmax of [3H]DPAT binding to 5-HT1A sites in the hippocampus. By contrast, this effect was not observed if clonazepam was delivered into the dorsal raphe nucleus by osmotic minipumps. The binding of [3H]paroxetine to 5-HT reuptake sites was increased by the treatment with clonazepam. The present observations indicate that clonazepam produces a reduction of serotonin turnover rate in the hippocampus of the rat concomitant with a down-regulation of 5-HT1A binding sites, probably by an effect at the forebrain projections. There is also an up-regulation of the serotonin transporter, which might contribute to a reduction in the synaptic availability of serotonin during clonazepam treatment.

Growth hormone response to apomorphine in panic disorder: comparison with major depression and normal controls

Several lines of evidence suggest that dopamine might be involved in anxiety states. In the present study we assessed the growth hormone (GH) response to 0.5 mg apomorphine (a dopaminergic agonist) in 10 male drug-free inpatients meeting Research Diagnostic Criteria for panic disorder who were compared with 10 male major depressive inpatients and 10 male normal controls. The three groups differed significantly in the GH peak response (mean +/- SD): 27.8 +/- 12.5 ng/ml in panics, 5.4 +/- 4.0 ng/ml in major depressives, and 25.8 +/- 11.3 ng/ml in normal controls (F(2,27) = 15.3; P = 0.00003). Although there were significant differences between panics and major depressives (P = 0.00004), and between major depressives and controls (P = 0.00004), panics did not significantly differ from controls. These results do not support the hypothesis of an overlap between panic and affective disorders, and suggest that the hypothalamo-GH-somatomedin axis could be intact in panic disorder.

Decreased benzodiazepine receptor binding in panic disorder measured by IOMAZENIL-SPECT. A preliminary report

Single photon emission tomography (SPECT) imaging of the central benzodiazepine receptor (BZr) became possible with the newly developed ligand 123I-IOMAZENIL. The BZr binding was investigated in ten patients with panic disorder (PP) compared to ten epileptic patients (EP). Panic patients had lower IOMAZENIL uptake rates in the frontal, occipital and temporal cortex than EP indicating the involvement of the BZr complex in panic disorder.

Modulation of 5HT1A receptors in the hippocampus and the raphe area of rats treated with clonazepam

1. Clonazepam is one of the most potent benzodiazepines known to decrease the activity of the central serotonergic systems. The acute and subchronic administration of clonazepam reduced serotonin (5HT) turnover rate in the hippocampus of the rat, as determined by the ratio of the monoamine and its metabolite, 5-hydroxyindoleacetic acid. 2. The modulation of 5HT binding sites and 5HT1A receptors by the administration of clonazepam for various periods of time were studied in the hippocampus and the raphe area by experiments with radioligands. 3. The density of [3H]5HT recognition sites increased in the hippocampus of clonazepam-treated rats in a dose- and time-dependent manner. This increase was impaired by the simultaneous administration of the 5HT agonist 5-methoxy-N,N-dimethyltryptamine. The affinity of this binding did not significantly change. This observation might indicate an increase in some of the 5HT receptors or an increase of the uptake site. 4. The binding parameters for [3H]DPAT, Bmax and Kd, decreased in the hippocampus but not in the raphe area of clonazepam-treated rats. It seems that the presynaptic reduction in 5HT function, resulting in the decrease of its availability at the synaptic space, modifies the corresponding 5HT recognition sites. 5. These changes could be related to the anxyolitic activity or the withdrawal symptoms of benzodiazepines.

Dopaminergic function in panic disorder: comparison with major and minor depression

Several lines of evidence suggest that dopamine might be involved in anxiety states. In this study, we assessed the growth hormone (GH) response to apomorphine (a dopaminergic agonist) 0.5 mg SC in nine drug-free inpatients meeting Research Diagnostic Criteria (RDC) for panic disorder who were age-matched and gender-matched with nine major depressive, and nine minor depressive inpatients. The three groups differed significantly in their mean GH peak response: 5.29 +/- 2.75 ng/ml in major depressives, 26.27 +/- 12.71 ng/ml in minor depressives, and 37.28 +/- 10.58 ng/ml in panics, with a significantly higher response in panic than in either minor or major depressive patients. These results support dopaminergic overactivity in panic disorder as compared with major and minor depression.

Anxiety disorders in children and adolescents: clinical and related issues in pharmacological treatment

Anxiety disorders in children and adolescents are receiving more attention from clinicians and researchers. Psychopharmacological approaches to controlling symptoms of anxiety are possible as part of a multi-model treatment approach. This paper provides an overview of some recent findings in child and adolescent anxiety disorders that may influence treatment decisions. It also reviews studies of the use of benzodiazepines and tricyclic antidepressants in treating children and adolescents who suffer from anxiety disorders, and suggests methods of integrating pharmacological treatment with other modalities in these disorders.

Panic attacks. A neurochemical overview of models and mechanisms

The delineation of panic disorder as a distinct diagnostic entity has provided renewed impetus for research into panic. This review describes and examines the range of neurobiological theories of panic attacks. It illustrates the diversity of mechanisms that have been invoked to explain the production of panic attacks, and which have influenced much of the current thinking about the neurochemistry of anxiety.

Psychopharmacological properties of calcium channel inhibitors

The previous decade has witnessed a major expansion of knowledge of the role played by voltage-sensitive calcium channels in the function of the central nervous system. Significant progress in the field has been made possible with the broadening use of organic calcium channel inhibitors (CCIs, Ca2+ antagonists), until recently considered almost exclusively as peripherally active antianginal and antiarrhythmic drugs. CCIs, however, do penetrate the blood-brain barrier from the periphery. Autoradiographic studies have established a highly heterogeneous distribution of CCI recognition sites within the brain. The existing evidence suggests that CCIs have marked psychotropic properties. The profile of their central activity is unique and spans a wide range of effects. Nevertheless, question regarding potentially confounding potent peripheral effects of these drugs remain. This paper reviews the psychopharmacology of CCIs, concentrating on preclinical data, but including supportive clinical and biochemical evidence as well. It focuses on these drugs' antidepressant, antidopaminergic (neuroleptic-like), anxiolytic and anticonvulsant effects. CCIs may also modify the reinforcing properties of some addictive drugs.

The pharmacology of human anxiety

The human pharmacology of anxiety disorders, including panic disorder, is detailed. The major theories center around the role of benzodiazepine receptor, noradrenergic and serotonergic dysfunction. The contribution that challenge tests with lactate, hyper- and hypocapnia, beta- and alpha-2-adrenoceptor agonists, peptides, pentylenetetrazol, and caffeine make to our understanding of the biological basis of anxiety and these major theories are described and discussed.