Fear and the brain: where have we been, and where are we going?

Sex differences in brain maturation in maltreatment-related pediatric posttraumatic stress disorder

BACKGROUND

Recent investigations suggested that pediatric posttraumatic stress disorder (PTSD) is associated with adverse brain development. However, sex differences are poorly understood.

METHODS

In this study, 61 medically healthy children and adolescents (31 males and 30 females) with chronic PTSD secondary to abuse, who had similar trauma and mental health histories, and 122 healthy controls (62 males and 60 females) underwent comprehensive psychiatric assessments and an anatomical MRI brain scan.

RESULTS

When gender groups were analyzed separately, findings of larger prefrontal lobe CSF volumes and smaller midsagittal area of the corpus callosum subregion 7 (splenium) were seen in both boys and girls with maltreatment-related PTSD compared to their gender-matched comparison subjects. Subjects with PTSD did not show the normal age related increases in the area of the total corpus callosum and its region 7 (splenium) compared to non-maltreated subjects; however, this finding was more prominent in males with PTSD. Significant sex by group effects demonstrated smaller cerebral volumes and corpus callosum regions 1 (rostrum) and 6 (isthmus) in PTSD males and greater lateral ventricular volume increases in maltreated males with PTSD than maltreated females with PTSD.

CONCLUSIONS

These data suggest that there are sex differences in the brain maturation of boys and girls with maltreatment-related PTSD. Longitudinal MRI brain investigations of childhood PTSD and the relationship of gender to psychosocial outcomes are warranted.

The human amygdala and the emotional evaluation of sensory stimuli

A wealth of animal data implicates the amygdala in aspects of emotional processing. In recent years, functional neuroimaging and neuropsychological studies have begun to refine our understanding of the functions of the amygdala in humans. This literature offers insights into the types of stimuli that engage the amygdala and the functional consequences that result from this engagement. Specific conclusions and hypotheses include: (1) the amygdala activates during exposure to aversive stimuli from multiple sensory modalities; (2) the amygdala responds to positively valenced stimuli, but these responses are less consistent than those induced by aversive stimuli; (3) amygdala responses are modulated by the arousal level, hedonic strength or current motivational value of stimuli; (4) amygdala responses are subject to rapid habituation; (5) the temporal characteristics of amygdala responses vary across stimulus categories and subject populations; (6) emotionally valenced stimuli need not reach conscious awareness to engage amygdala processing; (7) conscious hedonic appraisals do not require amygdala activation; (8) activation of the amygdala is associated with modulation of motor readiness, autonomic functions, and cognitive processes including attention and memory; (9) amygdala activations do not conform to traditional models of the lateralization of emotion; and (10) the extent and laterality of amygdala activations are related to factors including psychiatric status, gender and personality. The strengths and weakness of these hypotheses and conclusions are discussed with reference to the animal literature.

Human models as tools in the development of psychotropic drugs

Despite the growing means devoted to research and development (R α D) and refinements in the preclinical stages, the efficiency of central nervous system (CMS) drug development is disappointing. Many drugs reach patient studies with an erroneous therapeutic indication andlor in incorrect doses. Apart from the first clinical studies, which are conducted in healthy volunteers and focus only on safety, iolerability, and pharmacokinetics, drug development mostly relies on patient studies. Psychiatric disorders are characterized by heterogeneity and a high rate of comorbidity. It is becoming increasingly difficult to recruit patients for clinical trials and there are many confounding factors in this population, for example, those related to treatments. In order to keep patient exposure and financial expenditure to a minimum, it is important to avoid ill-designed and inconclusive studies. This risk could be minimized by gathering pharmacodynamic data earlier in development and considering that the goal of a phase 1 plan is to reach patient studies with clear ideas about the compound's pharmacodynamic profile, its efficacy in the putative indication (proof of concept), and pharmacokinetic/pharmacodynamic relationships, in addition to safety, tolerability, and pharmacokinetics. Human models in healthy volunteers may be useful tools for this purpose, but their use necessitates a global adaptation of the phase scheme, favoring pharmacodynamic assessments without neglecting safety. We are engaged in an R α D program aimed to adapt existing models and develop new paradigms suitable for early proof of concept substantiation.

Brain structures in pediatric maltreatment-related posttraumatic stress disorder: a sociodemographically matched study

BACKGROUND

Previous investigations suggest that maltreated children evidence alterations of chemical mediators of stress and adverse brain development. Previous anatomical magnetic resonance imaging (MRI) brain studies have not controlled for socioeconomic status.

METHODS

In this study, 28 psychotropic naïve children and adolescents with maltreatment-related posttraumatic stress disorder (PTSD) and 66 sociodemographically similar healthy control subjects underwent comprehensive clinical assessments and anatomical MRI brain scans.

RESULTS

Compared with control subjects, subjects with PTSD had smaller intracranial, cerebral, and prefrontal cortex, prefrontal cortical white matter, and right temporal lobe volumes and areas of the corpus callosum and its subregions (2, 4, 5, 6, and 7), and larger frontal lobe cerebrospinal fluid (CSF) volumes than control subjects. The total midsagittal area of corpus callosum and middle and posterior regions remained smaller in subjects with PTSD, whereas right, left, and total lateral ventricles and frontal lobe CSF were proportionally larger than in control subjects, after adjustment for cerebral volume. Brain volumes positively correlated with age of onset of PTSD trauma and negatively correlated with duration of abuse. Significant gender x group effect demonstrated greater lateral ventricular volume increases in maltreated male subjects with PTSD than maltreated female subjects with PTSD. No hippocampal differences were seen.

CONCLUSIONS

These data provide further evidence to suggest that maltreatment-related PTSD is associated with adverse brain development. These data also suggest that male children may be more vulnerable to these effects.

Envolvimento dos receptores 5-HT2 da amígdala nos níveis de ansiedade induzidos pela exposição de ratos ao labirinto em cruz elevado

O efeito de microinjeções intra-amigdalóides do antagonista 5-HT2A/2C de receptores serotoninérgicos RP 62203 (1,0; 2,5; 5,0 mg) foi investigado em medidas tradicionais e etológicas (esquadrinhar, espreitar e explorações da extremidade) de ansiedade de ratos no labirinto em cruz elevado. A dose de 5,0 mg aumentou as porcentagens de entrada e de tempo nos braços abertos, sem alterar no número de entradas nos braços fechados. As categorias esquadrinhar, espreitar e explorações da extremidade também foram alteradas pela droga. As doses de 2,5 e 5,0 mg aumentaram o tempo gasto em esquadrinhar e diminuíram o tempo gasto em espreitar. O número de explorações da extremidade também foi aumentado pela injeção da droga na dose de 5,0 mg. Este padrão comportamental sugere um efeito ansiolítico do RP 62203. A participação dos receptores 5-HT2A/2C da amígdala na regulação desse efeito é discutida.

Molecular targets in the treatment of anxiety

Although the cathecholamine systems have long been the focus of drug therapy in anxiety and depression, the development of novel drugs specifically aimed at new targets within these traditional neurotransmitter systems and at targets outside of these systems is now propelling the field of drug development in anxiety. A greater understanding of regional brain networks implicated in stress, anxiety, and anxious behaviors has provided localized targets for anxiolytics. Within the serotonin and norepinephrine systems, increased understanding of postsynaptic receptor regulation with chronic treatment and cross-system effects of drug therapy have been critical in furthering our understanding of effective pharmacological interventions. Receptors within the glutamate, gamma-aminobutyric acid, and neuropeptide systems provide a rich diversity of drug targets, both in localization and function. While acknowledging significant clinical and biological differences between the various anxiety disorders, an important aspect of modern neurobiological research is to look for similarities among these disorders, given that they are highly comorbid with each other and often respond to the same spectrum of treatments. Here we review current views on both traditional and new molecular targets in the treatment of anxiety, realizing that the ultimate challenge in effective anxiolytic drug development may be achieving specificity in brain regions important in generating and sustaining anxiety.

Startle reactivity and anxiety disorders: aversive conditioning, context, and neurobiology

The aim of this article is to review studies on human anxiety using the startle reflex methodology and to apply the literature on context conditioning in rats to interpret the results. A distinction is made between cued fear (as in specific phobia), a phasic response to an explicit threat cue, and anxiety, a more sustained and future-oriented response not linked to a specific discrete cue. Experimentally, contextual fear, as opposed to cued fear, may best reflect the feeling of aversive expectation about potential future dangers that characterizes anxiety. Following a brief description of the neurobiology of cued fear and context conditioning, evidence is presented showing that anxious patients are overly sensitive to threatening contexts. It is then argued that the degree to which contextual fear is prompted by threat depends on whether the danger is predictable or unpredictable. Consistent with animal data, unpredictable shocks in humans result in greater context conditioning compared to predictable shocks. Because conditioning promotes predictability, it is proposed to use conditioning procedures to study the development of appropriate and inappropriate aversive expectations. Cued fear learning is seen as an adaptive process by which undifferentiated fear becomes cue-specific. Deficits in cued fear learning lead to the development of nonadaptive aversive expectancies and an attentional bias toward generalized threat. Lacking a cue for threat, the organism cannot identify periods of danger and safety and remains in a chronic state of anxiety. Factors that may affect conditioning are discussed.

Systemic administration of interleukin-1beta activates select populations of central amygdala afferents

The central nucleus of the amygdala (CeA) is activated robustly by an immune challenge such as the systemic administration of the proinflammatory cytokine interleukin-1beta (IL-1beta). Because IL-1beta is not believed to cross the blood-brain barrier in any significant amount, it is likely that IL-1beta elicits CeA cell recruitment by means of activation of afferents to the CeA. However, although many studies have investigated the origins of afferent inputs to the CeA, we do not know which of these also respond to IL-1beta. Therefore, to identify candidate neurons responsible for the recruitment of CeA cells by an immune challenge, we iontophoretically deposited a retrograde tracer, cholera toxin b-subunit (CTb), into the CeA of rats 7 days before systemic delivery of IL-1beta (1 microg/kg, i.a.). By using combined immunohistochemistry, we then quantified the number of Fos-positive CTb cells in six major regions known to innervate the CeA. These included the medial prefrontal cortex, paraventricular thalamus (PVT), ventral tegmental area, parabrachial nucleus (PB), nucleus tractus solitarius, and ventrolateral medulla. Our results show that after deposit of CTb into the CeA, the majority of double-labeled cells were located in the PB and the PVT, suggesting that CeA cell activation by systemic IL-1beta is likely to arise predominantly from cell bodies located in these regions. These findings may have significant implications in determining the central pathways involved in generating acute central responses to a systemic immune challenge.

Regulation of synaptic plasticity genes during consolidation of fear conditioning

In mammals, long-term memory induced by Pavlovian fear conditioning has been shown to be dependent on the amygdala during a protein and mRNA synthesis-dependent phase of memory consolidation. We have used genes identified in a kainic acid model of synaptic plasticity as in situ hybridization probes during the consolidation period after fear conditioning. We found that these genes were transcriptionally regulated in several brain areas only when stimuli were presented in a manner that supported behavioral learning and not after unpaired presentations or footshocks alone. Immediate early genes and neurofilament mRNA peaked approximately 30 min after conditioning, as expected. Interestingly, nurr-1, alpha-actinin, and 16c8 increased approximately 2-4 hr later, whereas neurogranin and gephyrin decreased during that time. Our results suggest that fear memory consolidation occurs within a broad neural circuit that includes, but is not limited to, the amygdala. Together, a broad array of transcriptionally regulated genes, encoding transcription factors, cytoskeletal proteins, adhesion molecules, and receptor stabilization molecules, appear to mediate the neural plasticity underlying specific forms of long-term memory in mammals.

Impaired fear conditioning in Alzheimer's disease

Classical conditioning of the fear response is a basic form of nondeclarative (nonconscious) memory that mediates both normal and pathological responses to aversive stimuli. Because fear conditioning critically depends on the amygdala, a medial temporal lobe structure that frequently undergoes significant pathological changes early in the course of Alzheimer's disease (AD), we hypothesized that fear conditioning would be impaired in patients with mild to moderate AD. We examined simple classical fear conditioning in a group of 10 patients with probable AD and 14 demographically matched, neurologically intact elderly controls. During conditioning, one stimulus (e.g. a green rectangle, the conditioned stimulus (CS+)), was paired with an aversive stimulus (a loud noise, the unconditioned stimulus (US)) using a partial reinforcement conditioning schedule. The opponent color (e.g. red rectangle), the CS-, was never paired with the US. The elderly controls acquired robust fear responses as demonstrated by their differential skin-conductance responses to the CS+ and CS-. In contrast, the AD group showed a marked impairment in conditioning, failing to exhibit significant conditioned fear responses. This failure to acquire conditioned responses could not be attributed to diminished responding by patients, relative to controls, to the aversive US. The results indicate that fear conditioning, an amygdala-dependent form of memory, is impaired in AD. These findings complement previous reports of impairments in declarative emotional memory in AD by demonstrating that a basic form of nondeclarative emotional memory is also impaired in AD.

Cholinergic activation of the basolateral amygdala regulates unlearned freezing behavior in rats

Recent evidence suggests that the basolateral amygdala (BLA) is involved in the expression of freezing behavior in rats. This study investigated the effects of unilateral phthalic acid (PA) lesions of the nucleus basalis magnocellularis (NBM) on fear-motivated behavior in response to a natural predator-stimulus. Such lesions preferentially disrupt the cholinergic projection to the BLA. Rats were placed in a chamber containing either real or fake cat hair, and the amount of time spent freezing and the number of contacts made with the stimulus were measured. Compared with Sham control rats, the PA NBM-lesioned rats displayed significantly less freezing in the presence of the cat hair. Both the Sham and lesioned rats made fewer contacts with the real than the fake cat hair. Pre-testing intra-BLA infusion of the direct muscarinic cholinergic agonist oxotremorine ipsilateral to the PA NBM-lesion attenuated the freezing deficit. The indirect non-specific cholinergic agonist physostigmine increased the time spent freezing in Sham rats, but did not attenuate the freezing deficit in the NBM-lesioned rats. Sham and NBM-lesioned rats given oxotremorine infusions made fewer contacts with either the real or the fake cat hair. The PA NBM-lesion did not affect open field activity. These findings indicate that muscarinic cholinergic activation in the BLA from the NBM influences fear-motivated freezing behavior.

rCBF differences between panic disorder patients and control subjects during anticipatory anxiety and rest

BACKGROUND

Our goal was to identify brain structures involved in anticipatory anxiety in panic disorder (PD) patients compared to control subjects.

METHODS

Seventeen PD patients and 21 healthy control subjects were studied with H(2)(15)O positron emission tomography scan, before and after a pentagastrin challenge.

RESULTS

During anticipatory anxiety we found hypoactivity in the precentral gyrus, the inferior frontal gyrus, the right amygdala, and the anterior insula in PD patients compared to control subjects. Hyperactivity in patients compared to control subjects was observed in the parahippocampal gyrus, the superior temporal lobe, the hypothalamus, the anterior cingulate gyrus, and the midbrain. After the challenge, the patients showed decreases compared to the control subjects in the precentral gyrus, the inferior frontal gyrus, and the anterior insula. Regions of increased activity in the patients compared to the control subjects were the parahippocampal gyrus, the superior temporal lobe, the anterior cingulate gyrus, and the midbrain.

CONCLUSIONS

The pattern of regional cerebral blood flow activations and deactivations we observed both before and after the pentagastrin challenge was the same, although different in intensity. During anticipatory anxiety more voxels were (de)activated than during rest after the challenge.

The Danish PET/depression project: clinical symptoms and cerebral blood flow. A regions-of-interest analysis

OBJECTIVE

We wanted to explore associations between clinical symptoms of depression and the blood flow to specific regions of the brain. Furthermore, we wanted to compare the regions-of-interest (ROI) method with the functions-of-interest (FOI) approach.

METHOD

The resting blood flow to 42 ROI in the brain was obtained with positron emission tomography (PET) imaging in 42 representative in-patients with major depression and 47 matched healthy controls.

RESULTS

The patients had increased blood flow to hippocampus, cerebellum, anterior cingulate gyrus, and the basal ganglia. A strong negative correlation was found between the degree of psychomotor retardation of the patients and the blood flow to the dorsolateral and supraorbital prefrontal cortices. The total Hamilton score was correlated with the blood flow to the hippocampus.

CONCLUSION

Our findings support the notion that depressed patients have disturbances in the loops connecting the frontal lobes, limbic system, basal ganglia, and cerebellum.

Central mechanisms involved with catabolism

PURPOSE OF REVIEW

Catabolism conjures up an end-metabolic process in which muscle and fat tissue are broken down into their constituent parts to provide nutrients for the body, secondary to a noxious stimulus that prevents the organism from adequately nourishing itself. However, catabolism is a primary event, initiated in the brain in response to perceived or real stresses or noxious stimuli, which has a secondary effect of inhibiting food intake and consequently the break down of skeletal muscle and adipose tissues to provide nutrients for the body to survive.

RECENT FINDINGS

This is achieved via a cascade of neurohormonal monoaminergic and peptidergic mediators in the central nervous system, invoking the cortex, the limbic system and the hypothalamus. Among the most detailed mediators studied are corticotropin-releasing factor and serotonin which, via the hypothalamic-pituitary-adrenal axis and the sympathetic and parasympathetic nervous system, stimulate catecholamines and cortisol and inhibit anabolic hormones, insulin, leptin, ghrelin, including neuropeptide Y and other neuropeptides, among them the paracrine-acting cytokines. Simultaneously, there occurs stimulation of the counter-regulatory hormones cortisol, glucagon and the melanocortin family of neuropeptides.

SUMMARY

The net effect is anorexia, with the inhibition of food intake, body weight loss, delayed gastric emptying and functions, the stimulation of gluconeogenesis, glycogenolysis and ketogenesis as sources of metabolic fuel, which if unabated leads ultimately to cachexia. The use of antagonists and the removal of stress or noxious stimuli experimentally test different pathways of this dynamic metabolic picture. Several studies have demonstrated important progress towards our understanding of the central mechanisms involved in anorexia and weight loss, which we summarize in this review.

Neuroimaging studies in post-traumatic stress disorder

The authors review some of the advances that have been made in understanding the structural, biochemical, and functional neuroanatomy of post-traumatic stress disorder (PTSD). First, the authors review the primary brain regions that had been hypothesized a priori, from the phenomenology and neurobiology of PTSD, to be implicated in the pathophysiology. Next, they review findings from neuroimaging studies of these brain regions in PTSD, and explain the various experimental methods and imaging technologies used in these studies. A broader perspective, including a discussion of additional brain areas that may be involved in PTSD, is synthesized. The authors conclude with a rationale and approach for studies testing sharply defined hypotheses and those using multidisciplinary strategies that integrate neuroimaging data with other cognitive, biologic, and genetic tools to study this complex disorder.

Phthalic acid amygdalopetal lesion of the nucleus basalis magnocellularis induces reversible memory deficits in rats

The basolateral amygdala (BLA) is extensively implicated in emotional learning and memory. The current study investigated the contribution of cholinergic afferents to the BLA from the nucleus basalis magnocellularis in influencing aversive learning and memory. Sprague-Dawley rats were given permanent unilateral phthalic acid (300 ng) lesions of the nucleus basalis magnocellularis and were chronically implanted with cannulas aimed at the ipsilateral BLA. Lesioned rats showed a pronounced inhibitory avoidance task retention deficit that was attenuated by acute posttraining infusions of the muscarinic cholinergic agonist oxotremorine (4 ng) or the indirect agonist physostigmine (1 microg) into the BLA. Continuous multiple-trial inhibitory avoidance training and testing revealed that lesioned rats have a mild acquisition deficit, requiring approximately 1 additional shock to reach the criterion, and a pronounced consolidation deficit as indicated by a shorter latency to enter the shock compartment on the retention test. Because lesioned rats did not differ from sham-operated controls in performance on a spatial water maze task or in shock sensitivity, it is not likely that the memory impairments produced by the phthalic acid lesions are due to any general sensory or motor deficits. These findings suggest that the dense cholinergic projection from the nucleus basalis magnocellularis to the BLA is involved in both the acquisition and the consolidation of the aversive inhibitory avoidance task.

Cat odour exposure increases the expression of wolframin gene in the amygdaloid area of rat

The aim of the present study was to find the genes expressed in the amygdaloid area after exposure to cat odour. Cat odour exposure was used to induce the ethologically relevant fear response in male rats. The differential expression of genes was analyzed using the cDNA Representational Difference Analysis (RDA). The differentially expressed clones were identified by sequencing and database search. Reverse transcription-polymerase chain reaction (RT-PCR) was applied to confirm the differences found by the RDA. Exposure of rats to cat odour induced avoidance of odour stimulus and suppressed the exploratory activity of animals. We found that during the cat odour exposure, several genes with various functions were activated in the amygdaloid area. Among the identified genes, we found the activation of the wolframin gene. RT-PCR confirmed quantitative elevation in the levels of wolframin transcripts in the amygdaloid area. This study supports the role of wolframin in the regulation of emotional behaviour.

The role of the amygdala in signaling prospective outcome of choice

Can brain activity reveal a covert choice? Making a choice often evokes distinct emotions that accompany decision processes. Amygdala has been implicated in choice behavior that is guided by a prospective negative outcome. However, its specific involvement in emotional versus cognitive processing of choice behavior has been a subject of controversy. In this study, the human amygdala was monitored by functional magnetic resonance imaging (fMRI) while subjects were playing in a naturalistic choice paradigm against the experimenter. In order to win, players had to occasionally choose to bluff their opponent, risk "getting caught," and suffer a loss. A critical period, when choice has been made but outcome was still unknown, activated the amygdala preferentially following the choice that entailed risk of loss. Thus, the response of the amygdala differentiated between subject's covert choice of either playing fair or foul. These results support a role of the amygdala in choice behavior, both in the appraisal of inherent value of choice and the signaling of prospective negative outcomes.

Conditioned memory modulation, freezing, and avoidance as measures of amygdala-mediated conditioned fear

Three conditioned aversive responses were used to infer the existence of an unobservable central state of "conditioned fear," and the roles of certain amygdala subregions in producing these responses were investigated. Rats received tone-shock pairings in one compartment of a shuttle box and no tones or shocks in the other, distinctive, compartment. They were then trained to find food in one arm of a Y-maze. After the final training trial they were exposed to different sets of stimuli in the shuttle box with no shock. Twenty-four hours later rats that had received immediate posttraining exposure to the conditioned stimuli (in the shock-paired compartment) made significantly more correct responses on the Y-maze than rats that had been exposed to the neutral stimuli (in the no-shock compartment) or rats that had received delayed posttraining exposure to the conditioned stimuli. This constitutes a demonstration of posttraining memory modulation by conditioned aversive stimuli. Freezing increased during posttraining exposure to the conditioned stimuli compared to the neutral stimuli. When subsequently allowed to move freely between the two compartments, the rats in all groups also showed significant conditioned avoidance of the compartment containing the conditioned stimuli. In a second experiment the effects of lesions confined to specific parts of the amygdala on the three conditioned responses (memory modulation, freezing, avoidance) were tested. Lesions of the central nucleus impaired all three conditioned responses; lesions of the medial nucleus impaired conditioned modulation and avoidance. These lesions had no effect on freezing during the training trials. Lesions of the lateral and basolateral nuclei attenuated freezing during both training and testing. The findings suggest that the central and medial nuclei of the amygdala may be important parts of neural circuits mediating conditioned responses that constitute conditioned aversive states, but that conditioned freezing may be mediated independently.

The effects of safety-seeking behavior and guided threat reappraisal on fear reduction during exposure: an experimental investigation

We examined the effects of safety-seeking behavior and guided threat focus and reappraisal on fear reduction during exposure. Participants (N=46) displaying marked claustrophobic fear were randomized to one of three 30-min exposure conditions: (a) guided threat focus and reappraisal; (b) safety-behavior utilization; or (c) exposure only control. Tripartite outcome assessments during a behavioral approach test, along with measures of suffocation and restriction fears were obtained at pre- and post-treatment, and at a 2-week follow-up. Treatment process measures were collected throughout treatment and consisted of indices of fear activation; within and between-trial fear habituation; and suffocation and entrapment expectancies. Measures of safety behavior utilization and attentional focus were also collected to assess the integrity of the experimental manipulations. Consistent with prediction, those encouraged to utilize safety-behaviors during exposure showed significantly more fear at post-treatment and follow-up relative to those encouraged to focus and reevaluate their core threat(s) during exposure. Moreover, growth curve analyses of treatment process data analyses revealed that safety-behavior utilization exerted a detrimental effect on between-trial habituation; whereas guided threat reappraisal enhanced between-trial habituation.

Elevated T-maze as an animal model of memory: effects of scopolamine

The elevated T-maze (ETM) is a putative model for the assessment of anxiety and memory in rodents. This study was designed to further evaluate the utility of the ETM in the study of memory processes. We compared the performance of rats in the ETM, the water maze (WM) and the two-way avoidance task (TWA), after pretreatment with scopolamine (SCO; 0.3 or 1.2 mg/kg i.p.). In the ETM, rats were first trained to meet the criterion of remaining inside the enclosed arm for 300 seconds. Seventy-two hours after training, a retrieval test session was performed. At the lower dose, SCO impaired performance in the retrieval session on all three tasks, whereas in the training session an effect was noted only on the WM task. At the higher dose, SCO impaired the performance of rats in the training sessions for ETM and WM, but not TWA. In a fourth experiment using the elevated plus-maze, SCO showed anxiolytic-like effects at the higher dose only. In conclusion, the effects of SCO in rats submitted to the ETM were dose dependent, with the lower dose exerting a selective effect detected only on retrieval, whereas the higher dose induced motor effects that disrupted inhibitory avoidance acquisition, resulting in impaired retrieval. The results are discussed in terms of the utility of the ETM in the study of drug effects and the neurobiological mechanisms underlying anxiety, learning and memory.

Non-human primate models for investigating fear and anxiety

Non-human primates exhibit similar physiological and behavioral responses to anxiety-inducing situations as humans and have, in fact, been successfully employed in both conditioned (i.e. conflict paradigms) and ethologically based tests of fear/anxiety (i.e. involuntary isolation, social interaction, human threat, predator confrontation). In the last decade, a renewed and growing interest in non-human primate models has resulted from the use of the small callitrichid species in behavioral pharmacology and neuroscience. This review focuses on the available non-human primate models for investigating fear/anxiety, addressing their advantages, shortcomings, and conceptual framework on which they are based. Lastly, a new ethologically based model to study anxiety and fear-induced avoidance in callitrichids--the marmoset predator confrontation test--is discussed.

Behavioral reactivity to stress: amplification of stress-induced noradrenergic activation elicits a galanin-mediated anxiolytic effect in central amygdala

Brain norepinephrine (NE) modulates many aspects of the stress response. The interaction between NE and neuropeptides such as galanin, with which it is closely associated and which may be released from noradrenergic terminals under conditions of high activity, has not been well studied. We therefore investigated the modulatory effects of galanin in the central nucleus of the amygdala (CeA) on behavioral responsivity to stress when activation of the noradrenergic system was amplified using the adrenergic autoreceptor antagonist yohimbine (2.5 mg/kg ip). Either immobilization stress or yohimbine alone had anxiogenic effects on rat behavior in the elevated plus maze. However, yohimbine pretreatment before stress produced a paradoxical anxiolytic response, which we hypothesized was attributable to galanin release in CeA. Microdialysis verified that yohimbine amplified NE release in CeA during immobilization stress, and also showed that whereas there was no detectable change in galanin release in CeA during stress alone, there was an increase during immobilization stress after yohimbine pretreatment. Bilateral administration of the galanin antagonist M40 into CeA before stress blocked the anxiolytic influence of yohimbine pretreatment. Exogenous galanin mimicked the anxiolytic effect of yohimbine pretreatment, and this too was blocked by M40. These results suggest that amplifying the noradrenergic response to stress can recruit galanin release in CeA, which buffers the anxiety-like behavioral response to acute stress. The balance between noradrenergic and peptidergic neurotransmission may be modified by prior stress, drug treatment or genetic variability, and may represent a novel target for treatment of stress-related neuropsychiatric disorders.

Symptomatic and syndromal anxiety and depression

The diagnosis of anxiety disorders and major depression can be reliably made based on signs and symptoms. However there are significant limitations to the current system of classification including overlapping criteria, high comorbidity, and the issue of subthreshold syndromes. The literature on treatment response documents that selective serotonin reuptake inhibitors are effective in the treatment of the various anxiety disorders, including when comorbid major depression is present. The literature also suggests that tricyclic antidepressant medications have superior benefits over selective serotonin reuptake inhibitors in major depression. Examination of the functional anatomy of the fear and reward systems may shed light on the underlying processes in the anxiety and depressive disorders. Such an approach points out the importance of addressing avoidance behaviors, which may be more responsive to cognitive behavioral treatments than pharmacological agents.

Imaging learning and memory: classical conditioning

The search for the biological basis of learning and memory has, until recently, been constrained by the limits of technology to classic anatomic and electrophysiologic studies. With the advent of functional imaging, we have begun to delve into what, for many, was a "black box." We review several different types of imaging experiments, including steady state animal experiments that image the functional labeling of fixed tissues, and dynamic human studies based on functional imaging of the intact brain during learning. The data suggest that learning and memory involve a surprising conservation of mechanisms and the integrated networking of a number of structures and processes.

Affective neuroscience and the development of social anxiety disorder

Recent studies on the familial distribution and longitudinal outcome of SAD emphasize developmental aspects of the syndrome, consistent with the developmental psychopathology perspective. Key questions in this area concern factors that mediate familial transmission and that predict outcome. Prior studies provide incomplete answers to these questions. Recent studies in affective neuroscience suggest potential avenues for answering these questions. As reviewed in the current article, fMRI studies of face processing provide examples of such potentially informative research directions.

Potentiated amygdaloid auditory-evoked potentials and freezing behavior after fear conditioning in mice

Elucidation of cellular and molecular mechanisms underlying fear-related memory would greatly benefit from the possibility of combined behavioral and electrophysiological recordings in genetically modified mice. As a first step to this goal, we implanted adult C57BL/6J mice with recording electrodes aimed at the basolateral amygdaloid complex and trained them in an auditory fear conditioning paradigm. After conditioning, animals with paired tone and footshock presentation showed not only intensified freezing behavior lasting for 2 days, but also increases, lasting 4 days, in slope and amplitude of the most negative component of auditory-evoked potentials triggered by the conditioned stimulus. These effects could not be observed in animals with unpaired tone and footshock presentation. Thus, our data show that a long-lasting association of a former neutral tone with an aversive situation is accompanied by a long-lasting increase of auditory-evoked potentials in freely moving mice. However, extinction of the potentiation of auditory-evoked potentials and freezing behavior followed different time courses, thus making a direct relationship between these responses unlikely.

Adolescent fears as predictors of depression

BACKGROUND

Recent studies raise questions on the relationship between adolescent fears and risk for major depression.

METHODS

An epidemiologic sample of 776 young people received psychiatric assessments in 1983, 1985-1986, and 1992. Prospective associations were examined between fears in adolescence and future episodes of major depression.

RESULTS

Both overall level of fears and specific fear of dark in adolescence predicted future risk for major depression.

CONCLUSIONS

Relatively high levels of fear in adolescence represent a risk factor for later episodes of major depression.

Serotonin, testosterone and alcohol in the etiology of domestic violence

In a previous study we administered the panicogenic agent sodium lactate to a select group of perpetrators of domestic violence and comparison groups. Results of that study showed that perpetrators exhibited exaggerated lactate-induced fear, panic and rage. In this current study, we compared the cerebral spinal fluid (CSF) concentrations of 5-hydroxyindoleacetic acid (5-HIAA) and testosterone obtained from perpetrators of domestic violence and a group of healthy comparison subjects. All subjects were assessed for DSM-III-R diagnoses. Perpetrators with alcohol dependence (DV-ALC) (n=13), perpetrators without alcohol dependence (DV-NALC) (n=10) and healthy comparison subjects (HCS) (n=20) were clinically assessed using the Spielberger Trait Anxiety, Brown-Goodwin Aggression Scale, Buss Durkee Hostility Inventory and Straus Conflict Tactics. Following an overnight fast and bed rest, subjects received a lumbar puncture to obtain CSF concentrations of 5-HIAA and testosterone. Perpetrators scored significantly higher on measures of aggression than HCS. DV-NALC had significantly lower concentrations of CSF 5-HIAA and higher Straus Conflict Tactics (CT) physical violence scores than DV-ALC and HCS. DV-ALC had significantly higher concentrations of CSF testosterone than DV-NALC. DV-ALC also had significantly higher Straus CT physical violence scores than HCS. DV-NALC and DV-ALC differed on 5-HIAA concentrations, testosterone concentrations, Straus CT physical violence scores and alcohol dependence. These results suggest that DV-NALC and DV-ALC groups could have different biological mechanisms mediating domestic violence.

Learning in respiratory control

In this article, it is argued that learning participates to fulfill the metabolic requirements by adapting respiratory control to changing internal and external states. Recent classical-conditioning experiments in newborn mice or adult rats show the close link between conditioned respiratory and arousal responses. The conditioned fear model may be a suitable and largely unexplored model of emotionally induced hyperventilation. The parabrachial nucleus and periacqueducal grey may play a pivotal role in the ventilatory component of conditioned fear. The sensitivity of breathing to conditioning in newborn and adult animals suggests that learning processes may shape breathing pattern throughout life.

Role of serotonergic and noradrenergic systems in the pathophysiology of depression and anxiety disorders

There is abundant evidence for abnormalities of the norepinephrine (NE) and serotonin (5HT) neurotransmitter systems in depression and anxiety disorders. The majority of evidence supports underactivation of serotonergic function and complex dysregulation of noradrenergic function, most consistent with overactivation of this system. Treatment for these disorders requires perturbation of these systems. Reproducible increases in serotonergic function and decreases in noradrenergic function accompany treatment with antidepressants, and these alterations may be necessary for antidepressant efficacy. Dysregulation of these systems clearly mediates many symptoms of depression and anxiety. The underlying causes of these disorders, however, are less likely to be found within the NE and 5HT systems, per se. Rather their dysfunction is likely due to their role in modulating, and being modulated by, other neurobiologic systems that together mediate the symptoms of affective illness. Clarification of noradrenergic and serotonergic modulation of various brain regions may yield a greater understanding of specific symptomatology, as well as the underlying circuitry involved in euthymic and abnormal mood and anxiety states. Disrupted cortical regulation may mediate impaired concentration and memory, together with uncontrollable worry. Hypothalamic abnormalities likely contribute to altered appetite, libido, and autonomic symptoms. Thalamic and brainstem dysregulation contributes to altered sleep and arousal states. Finally, abnormal modulation of cortical-hippocampal-amygdala pathways may contribute to chronically hypersensitive stress and fear responses, possibly mediating features of anxiety, anhedonia, aggression, and affective dyscontrol. The continued appreciation of the neural circuitry mediating affective states and their modulation by neurotransmitter systems should further the understanding of the pathophysiology of affective and anxiety disorders.

Sex differences in amygdala activation during the perception of facial affect

The cognitive and affective systems of the cerebral cortex are often more lateralized in males than females, but it is unclear whether these differences extend to subcortical systems. We used fMRI to examine sex differences in lateralized amygdala activity during happy and fearful face perception. Amygdala activation differed for men and women depending on the valence of the expression. Overall, males were more lateralized than females, but the direction differed between valence conditions. Happy faces produced greater right than left amygdala activation for males but not females. Both sexes showed greater left amygdala activation for fearful faces. These findings suggest that the lateralization of affective function may extend beyond the cortex to subcortical regions such as the amygdala.

Disrupting basolateral amygdala function impairs unconditioned freezing and avoidance in rats

Lesions of the lateral/basolateral amygdala nuclei (BLC) disrupt freezing behaviour in response to explicit or contextual cues (conditioned stimuli--CS) paired previously with footshock (unconditioned stimulus). This deficit in expression of defensive behaviour in response to conditioned stimuli is often interpreted as inability of lesioned rats to learn CS-US associations. However, findings of several studies indicate that BLC-lesioned rats can rapidly learn CS-US associations. Such findings suggest that lesioned rats can learn CS-US associations but are impaired in the expression of freezing behaviour. In the present study we report that both temporary inactivation (lidocaine) and permanent excitotoxic (NMDA) lesions of the BLC impair the unconditioned freezing and avoidance behaviours of rats in response to a novel fear-eliciting stimulus, a ball of cat hair. These findings suggest that the BLC influences the expression of freezing and avoidance behaviours, and/or that it potentiates rats' experience of fear. Along with prior evidence of spared memory for aversive learning after BLC lesions, these findings suggest that disrupted freezing to conditioned cues in BLC-lesioned rats does not necessarily reflect inability to form CS-US associations.

Projections from the nociceptive area of the central nucleus of the amygdala to the forebrain: a PHA-L study in the rat

The lateral capsular division (CeLC) of the central nucleus (Ce) of the amygdala, in the rat, has been shown to be the main terminal area of a spino(trigemino)-parabrachio-amygdaloid nociceptive pathway [Bernard & Besson (1990) J. Neurophysiol. 63, 473-490; Bernard et al. (1992) J. Neurophysiol. 68, 551-569; Bernard et al. (1993) J. Comp. Neurol. 329, 201-229]. The projections to the forebrain from the CeLC and adjacent regions were studied in the rat by using microinjections of Phaseolus vulgaris leucoagglutinin (PHA-L) restricted in subdivisions of the Ce and the basolateral amygdaloid nucleus anterior (BLA). Our data showed that the entire CeLC projects primarily and extensively to the substantia innominata dorsalis (SId). The terminal labelling is especially dense in the caudal aspect of the SId. The other projections of the CeLC in the forebrain were dramatically less dense. They terminate in the bed nucleus of the stria terminalis (BST) and the posterior hypothalamus (pLH). No (or only scarce) other projections were found in the remaining forebrain areas. The Ce lateral division (CeL) and the Ce medial division (CeM), adjacent to the CeLC, also project to the SId with slightly lower density labelling. However, contrary to the case of the CeLC, both the CeL and the CeM extensively project to the ventrolateral subnucleus of the BST (BSTvl) with a few additional terminals found in other regions of the lateral BST. Only the CeM projects densely to both the interstitial nucleus of the posterior limb of the anterior commissure and the caudal most portion of the pLH. The projections of the BLA are totally different from those of the Ce as they terminate in the dorsal striatum, the accumbens nucleus, the olfactory tubercle, the nucleus of olfactory tract and the rostral pole of the cingulate/frontal cortex. This study demonstrates that the major output of the nociceptive spino(trigemino)-parabrachio-CeLC pathway is to the SId. It is suggested that the CeLC-SId pathway could have an important role in anxiety, aversion and genesis of fear in response to noxious stimuli.

The anxiolytic-like effect of nicotine undergoes rapid tolerance in a model of contextual fear conditioning in rats

The effects of repeated administration of nicotine on contextual fear conditioning, locomotor activity, and pain threshold, were examined in rats. It was found that a single injection of nicotine prior to the training session (three 0.7-mA footshocks, each 0.5 s long), decreased the freezing reaction during the retest 24 h later. The locomotor activity was moderately enhanced, and the pain threshold remained unchanged. The baseline freezing measured immediately after administration of a single dose of nicotine was not significantly different from the saline-treated group. The anxiolytic-like effect of nicotine was as potent as that of midazolam, a benzodiazepine derivative. After five day-by-day injections, the anxiolytic-like effect of nicotine (0.6 mg/kg, sc) was no longer present, independently whether the last drug injection was given 24 h or 5 min (i.e., the sixth, additional, nicotine injection), prior to the training session. Thus, it appeared that the expression of tolerance to the nicotine-induced anxiolytic-like action did not require a direct stimulation of nicotinic receptors. Simultaneously, in this group of animals, nicotine caused a potent stimulation of locomotor activity in the open field test. The applied dosage and regimen of nicotine administration did not change rat pain threshold (flinch-jump test). Collectively, the present data showed for the first time, that short-term, intermittent, administration of nicotine was sufficient to induce tolerance to the anxiolytic-like effect of this drug, in the model of fear conditioning to context. Importantly, a clear dissociation between the locomotor and anxiolytic-like effects of nicotine was present. This effect appeared independent also of changes in rat pain threshold. The possible mechanisms of this phenomenon are discussed.

CNS region-specific oxytocin receptor expression: importance in regulation of anxiety and sex behavior

The oxytocin receptor (OTR) is differentially expressed in the CNS. Because there are multiple mechanisms by which the OTR can be transcriptionally induced, we hypothesized that differences in OTR expression may be explained by activation of distinct signal transduction pathways and may be critical for the control of anxiety and sex behaviors. To determine the regulation and functional significance of this expression, we infused female rats with modifiers of protein kinases before assaying for behavior and oxytocin receptor binding. In the ventromedial nucleus of the hypothalamus (VMH), estrogen-dependent induction of oxytocin receptors required protein kinase C activation, and oxytocin infused here promoted female sex behavior but had no effect on anxiety. In contrast, dopamine controlled tonic oxytocin receptor expression in the central nucleus of the amygdala (cAmyg) through activation of protein kinase A, and oxytocin infused here was anxiolytic but had no effect on female sex behavior. Therefore, we have identified brain region-specific regulation of the OTR in the VMH and cAmyg. Distinct signal transduction pathways regulating receptor expression and binding in each brain region may mediate in part the ability of oxytocin to exert these differential behavioral effects.

Fear and feeding in the nucleus accumbens shell: rostrocaudal segregation of GABA-elicited defensive behavior versus eating behavior

This study examined localization of positive versus negative motivational functions mediated by GABA circuits within the accumbens shell. Microinjections of a GABA(A) agonist (0, 25, 75, and 225 ng/0.5 microl muscimol) in rostral shell sites elicited appetitive increases in eating behavior. In contrast, microinjections in caudal shell sites elicited defensive burying or paw-treading behavior. Rats whose microinjections landed bilaterally outside of the accumbens shell did not display either behavior. Defensive treading elicited by caudal shell muscimol microinjection appeared to be a negative motivated response to threat (similar in parameters and orientation to normal defensive burying of a threatening electrified shock prod). The nucleus accumbens shell thus appears functionally heterogeneous in coding motivational valence. The demonstration that muscimol elicits positive eating behavior from rostral shell versus negative defensive behavior from caudal shell suggests in particular that GABAergic substrates of positive and negative types of motivated behavior in the nucleus accumbens shell are segregated along a rostrocaudal gradient.

Selective cognitive processing of drug cues in heroin dependence

Previous studies provide evidence for the selective processing of disorder related stimuli on anxiety, depression, and eating disorders. There exist some preliminary indications that selective processing of drug cues may be involved in drug craving and relapse that deserve further investigation. In order to investigate the role of processing bias in an abnormal motivational system, the attentional bias for drug related stimuli was studied in a heroin dependent population. Heroin dependent participants (n = 21) and control participants (n = 30) performed a supra- and subliminal heroin Stroop task and heroin craving was assessed. Heroin dependent participants showed a considerable attentional bias for supraliminally presented heroin cues. However, there was no evidence for a preattentive bias on the subliminal presented cues. Reaction time on heroin cues was significantly predicted by heroin craving-levels. Results indicate that selective processing may be related to motivational induced states in general. The finding are discussed in the context of selective information processing in general psychopathology and in motivational processes as addiction specifically.

Clinical features and co-morbidity of social phobics in Turkey

The aim of this study is to investigate the clinical features and frequency and importance of related co-morbid disorders of social phobia in a clinical sample. Eighty-seven patients meeting DSM-III-R diagnostic criteria for social phobia were studied. All patients were assessed by using a semi-structured socio-demographic form, the Structured Clinical Interview for DSM-III-R, Manual for the Structured Clinical Interview for DSM-III-R Personality Disorders, Liebowitz Social Anxiety Scale, Hamilton Rating Scale for Depression and Hamilton Rating Scale for Anxiety. Sixty-eight (78.2%) of the group were male, 19 (21.8%) were female. The ages varied between 16-58 years, with a mean of 26.2 years (SD = 8.5). Fifty-one point seven percent of the subjects were assessed as having a co-morbid axis I disorder, of which 12.6% consisted of panic disorder and 10.3% agoraphobia. An additional axis II disorder had been found in 67.8% of the subjects, and 54.0% of them had been diagnosed as having avoidant personality disorder. The frequency of co-morbid disorders in our social phobic sample is lower than most of the studies in the literature. The interface between social phobia and avoidant personality disorder needs to be studied and discussed further.

Neurobiology of generalized anxiety disorder

On reviewing the literature on GAD and trying to summarize the various developments in the field of neurobiology of GAD, we see that a range of hypotheses try to explore and integrate the observations found into potentially meaningful theories. Abnormal serotonergic and GABAergic function occur in many patients with GAD. Functional imaging data have shown increased cortical activity and decreased basal ganglia activity in patients with GAD, which reverses with treatment, but it is apparent that no one theory is sufficiently comprehensive to propose a unitary hypothesis for the development of GAD and other anxiety disorders. GAD is a relatively new diagnosable condition, first introduced into the classification system of psychiatric disorders in 1980, and since then has undergone a series of changes in its conceptualization, with some investigators questioning the existence of the condition as a distinct entity. Any inferences that may be drawn from various studies must be guarded, and it is appropriate to compare studies using the same diagnostic criteria. Significant research has been done and may lead to exciting new discoveries in the treatment of anxiety disorders in general and GAD in particular. Gray's model of behavioral inhibition, in which the septohippocampal system acts by assessing stimuli for the presence of danger and, when that is detected, activates the behavioral-inhibition circuit, provides a neuroanatomic conceptualization that has been expanded by preclinical research. Some exciting work has been done on CRF and the concept of development, vulnerability, and kindling and some investigators have contributed to this area of interest. This concept supports the hypothesis that a genetic predisposition, coupled with early stress, in the crucial phases of development may result in a phenotype that is neurobiologically vulnerable to stress and may lower an individual's threshold for developing anxiety or depression on additional stress exposure. The pharmaceutical industry is exploring treatment options using CRF antagonists, and research on other neuropeptides, especially NPY, will be of interest. Research on neurosteroids also may bring the opportunity for pharmacologic treatment approaches. Future research on the startle reflex and on the NMDA and the metabotropic glutamate receptors is important. Future studies of a more homogenous patient population and using more sophisticated techniques, such as molecular genetic strategies and better imaging techniques, may answer some of the outstanding questions.

Activation of ventrolateral medullary neurons projecting to spinal autonomic areas after chemical stimulation of the central nucleus of amygdala: a neuroanatomical study in the rat

Several studies have shown that the central nucleus of amygdala is involved in cardiovascular regulation. The control of this function may be mediated by activation of the ventrolateral medulla neurons that project to preganglionic neurons located in the intermediolateral nucleus of the spinal cord. The aim of the present study was to examine whether stimulation of the central nucleus of amygdala activated ventrolateral medulla neurons projecting to the intermediolateral nucleus. For this purpose, the injection of a retrograde tracer, the cholera toxin b subunit (CTb), into the intermediolateral nucleus of the T2 segment was combined with immunohistochemical detection of Fos protein following chemical stimulation of the central nucleus of amygdala. Results showed that retrogradely labeled neurons were found throughout the ventrolateral medulla. Moreover, chemical stimulation of the central nucleus of amygdala induced: (1) a decrease of arterial blood pressure; (2) an expression of Fos protein mainly in sub-populations of neurons located in the intermediate and caudal parts of the ventrolateral medulla; (3) a significantly higher number of double labeled neurons (CTb-immunoreactive/Fos-immunoreactive) in the rostral part of the ventrolateral medulla than in the other parts of this region. These results show that the central nucleus of amygdala influences the activity of brainstem neurons projecting to the intermediolateral nucleus. Data were discussed in terms of descending amygdalofugal pathways involved in the hypotension.

Inhibition of shock-induced foot tapping behaviour in the gerbil by a tachykinin NK1 receptor antagonist

The selective tachykinin NK1 receptor antagonist, 2-(R)-(1-(R)-3,5-Bis(trifluoromethyl)phenylethoxy)-3-(S)-(4-fluoro)phenyl-4-(3-oxo-1,2,4-triazol-5-yl)methylmorpholine (MK-869), has been recently described as a novel therapeutic approach for anxiety/depression. A frequently used model to establish the central nervous system (CNS) activity of tachykinin NK1 receptor antagonists is the inhibition of NK1 agonist-induced foot tapping in gerbils. In the present study, we demonstrate that foot tapping can also be induced in most, but not all, gerbils by footshock and associated cues. MK-869 (0.3-3 mg/kg, i.p.) dose-dependently blocked this foot tapping response. This effect was further shown to be due to selective NK1 receptor blockade, since (2S,3S)-cis-3(2-methoxybenzylamino)-2-phenylpiperidine (CP-99,994; 3 mg/kg, i.p.) inhibited foot tapping, whereas its less active enantiomer (2R,3R)-cis-3(2-methoxybenzylamino)-2-phenylpiperidine (CP-100,263; 3 mg/kg, i.p.) had no effect. Diazepam (1-10 mg/kg, i.p.) also inhibited foot tapping, whereas fluoxetine (10-30 mg/kg, i.p.) markedly increased this behaviour. The present data support the view that foot tapping in the gerbil is a behavioural response to an aversive stimulus, and is robustly inhibited by two NK1 receptor antagonists. The data support a role for tachykinin NK1 receptor antagonists as novel anxiolytic/antidepressants.

Environmental familiarization in rats: differential effects of acute and chronic nicotine

If an environment is familiar, rats will interact more with a novel object than if the environment is unfamiliar. In two experiments we used this behavioral tendency to assess the effects of nicotine on environmental familiarization (i.e., an elevated platform). As expected, rats given 2 min of exposure to the platform on 2 consecutive days (familiarization phase) interacted more with a novel object in a subsequent test than rats that had not experienced the platform until the test day. During the familiarization phase acute pretreatment with nicotine (0.6 and 1.8 mg/kg, subcutaneous) 10 min before platform exposure interfered with familiarization processes, as measured by object interaction on the drug-free test day. Behavioral measures of activity (e.g., turning and midline crosses) eliminated an account based on nicotine-induced motor impairment. Furthermore, this effect of acute nicotine on familiarization was not due to nonspecific effects of nicotine. Controls that received equivalent nicotine exposure temporally separated from platform exposure interacted more with the novel object than similarly treated controls that were unfamiliar with the platform on the test day. Interestingly, rats treated once daily with 0.6 mg/kg nicotine for 14 days before the familiarization phase (chronic condition) did not show a decrease in environmental familiarity. This dissociation extends a growing literature finding that the behavioral and neurobiological effects of nicotine differ, in part, after acute and chronic exposure. Indeed, acute nicotine (0. 2, 0.6, and 1.2 mg/kg) in the present report consistently decreased the amount of time spent with one paw on the edge of the platform; chronic nicotine did not affect this behavior.

Generalized anxiety disorder

The diagnosis of generalized anxiety disorder (GAD) was first introduced in 1980 with the publication of the Diagnostic and Statistical Manual of Mental Disorders, Third Edition (DSM-III) of the American Psychiatric Association. Prior to this, the diagnosis of "anxiety neurosis" was given to patients with symptoms similar to those now incorporated within the GAD category. Originally, GAD was created as a residual category within the anxiety disorders as a rubric for patients with serious anxiety problems but without panic attacks. Panic disorder therefore received far more research attention, and GAD was seen as a diagnosis of exclusion once panic disorder had been ruled out. It is now clear, however, that GAD is a serious psychiatric disorder that is more common than panic disorder and frequently encountered in primary care practice. Indeed, the primary care physician is more likely to see patients with pure GAD than is the psychiatrist. While the treatment of GAD is relatively straightforward, the diagnosis can be difficult. Hence, careful attention to several key symptomatic presentations is important.

Affect regulation, brain development, and behavioral/emotional health in adolescence

This paper addresses the importance of affect regulation (AR) in relation to a broad range of behavioral and emotional health problems that emerge during adolescence. AR is defined as the adaptive modulation of emotional experience to serve a goal or purpose. This conceptualization of AR emphasizes the use of cognitive skills to guide, inhibit, or modify emotion and behavior, including the expression of emotional responses, in learned, strategic ways-skills that ultimately underpin adult levels of social maturity and the ability to show "responsible" behavior across a range of emotional situations. Neurobehavioral systems that subserve these AR skills include areas of the inferior and orbital prefrontal cortex (PFC), with rich interconnections to several limbic structures and other cortical areas, including the dorsolateral PFC. Adolescence represents an important developmental period in the functional maturation of adult AR skills; it is also a critical time in the development of clinical disorders of AR (eg, rates of depression increase dramatically and gender differences in depression emerge). Maturational changes in AR that occur during adolescence-particularly with respect to the role of emotions influencing responsible decision making-are also relevant to understanding key aspects of the developmental pathways of some behavioral health problems, such as alcohol use and nicotine dependence. A strong case is made for developmental research in affective neuroscience aimed at this important maturational period, particularly the kind of transdisciplinary research leading toward mechanistic understanding of the development of adolescent-onset disorders. Improving understanding in these areas could ultimately lead to the development of early interventions in targeted high-risk populations, and has enormous clinical and social policy relevance.