Stress-induced impairment of fear extinction recall is associated with changes in neuronal activity patterns in PVT.

Treatment resistance of anxiety-related disorders often arises from an inappropriate fear expression, impairment in fear extinction, and spontaneous return of fear. Stress exposure is considered a high risk factor for neuropsychiatric disorders, but understanding of the long-term consequences of stress is limited, particularly when it comes to treatment outcome. Therefore, studying the consequences of acute stress would provide critical information on the role of stress in psychopathology. In the present study, we investigated the effect of acute immobilization stress on anxiety-like behavior and on conditioned fear memory. Our results demonstrate that prior stress exposure had no effect on anxiety-related behavior, fear acquisition, as well as fear extinction compared to non-stressed controls, but resulted in significantly higher rates of freezing during recall of extinction, indicating a consolidation failure. Further, immunohistochemical analysis of the expression of the immediate early gene c-Fos after recall of extinction revealed increased neuronal activity in the posterior paraventricular nucleus of the thalamus (PVT) in previously stressed animals compared to non-stressed controls. These results indicate, firstly, that acute stress affects long-term fear memory even after successful extinction training, and secondly, a strong involvement of the PVT in maladaptive fear responses induced by prior stress. Thus, stress-induced changes in PVT neuronal activity might be of importance for the pathophysiology of stress-sensitive anxiety-related psychiatric disorders, since exposure to an earlier acute stressor could counteract the success of therapy.

Genetically driven brain serotonin deficiency facilitates panic-like escape behavior in mice.

Multiple lines of evidence implicate brain serotonin (5-hydroxytryptamine; 5-HT) system dysfunction in the pathophysiology of stressor-related and anxiety disorders. Here we investigate the influence of constitutively deficient 5-HT synthesis on stressor-related anxiety-like behaviors using Tryptophan hydroxylase 2 (Tph2) mutant mice. Functional assessment of c-Fos after associated foot shock, electrophysiological recordings of GABAergic synaptic transmission, differential expression of the Slc6a4 gene in serotonergic neurons were combined with locomotor and anxiety-like measurements in different contextual settings. Our findings indicate that constitutive Tph2 inactivation and consequential lack of 5-HT synthesis in Tph2 null mutant mice (Tph2-/-) results in increased freezing to associated foot shock and a differential c-Fos activity pattern in the basolateral complex of the amygdala. This is accompanied by altered GABAergic transmission as observed by recordings of inhibitory postsynaptic currents on principal neurons in the basolateral nucleus, which may explain increased fear associated with hyperlocomotion and escape-like responses in aversive inescapable contexts. In contrast, lifelong 5-HT deficiency as observed in Tph2 heterozygous mice (Tph+/-) is able to be compensated through reduced GABAergic transmission in the basolateral nucleus of the amygdala based on Slc6a4 mRNA upregulation in subdivisions of dorsal raphe neurons. This results in increased activity of the basolateral nucleus of the amygdala due to associated foot shock. In conclusion, our results reflect characteristic syndromal dimensions of panic disorder and agoraphobia. Thus, constitutive lack of 5-HT synthesis influence the risk for anxiety- and stressor-related disorders including panic disorder and comorbid agoraphobia through the absence of GABAergic-dependent compensatory mechanisms in the basolateral nucleus of the amygdala.

Sickeningly Sweet: L-rhamnose stimulates Flavobacterium columnare biofilm formation and virulence.

Flavobacterium columnare, the causative agent of columnaris disease, causes substantial mortality worldwide in numerous freshwater finfish species. Due to its global significance and impact on the aquaculture industry continual efforts to better understand basic mechanisms that contribute to disease are urgently needed. The current work sought to evaluate the effect of L-rhamnose on the growth characteristics of F. columnare. While we initially did not observe any key changes during the total growth of F. columnare isolates tested when treated with L-rhamnose, it soon became apparent that the difference lies in the ability of this carbohydrate to facilitate the formation of biofilms. The addition of different concentrations of L-rhamnose consistently promoted the development of biofilms among different F. columnare isolates; however, it does not appear to be sufficient as a sole carbon source for biofilm growth. Our data also suggest that iron acquisition machinery is required for biofilm development. Finally, the addition of different concentrations of L-rhamnose to F. columnare prior to a laboratory challenge increased mortality rates in channel catfish (Ictalurus punctatus) as compared to controls. These results provide further evidence that biofilm formation is an integral virulence factor in the initiation of disease in fish.

Cannabinoid CB1 receptors in distinct circuits of the extended amygdala determine fear responsiveness to unpredictable threat.

The brain circuits underlying behavioral fear have been extensively studied over the last decades. Although the vast majority of experimental studies assess fear as a transient state of apprehension in response to a discrete threat, such phasic states of fear can shift to a sustained anxious apprehension, particularly in face of diffuse cues with unpredictable environmental contingencies. Unpredictability, in turn, is considered an important variable contributing to anxiety disorders. The networks of the extended amygdala have been suggested keys to the control of phasic and sustained states of fear, although the underlying synaptic pathways and mechanisms remain poorly understood. Here, we show that the endocannabinoid system acting in synaptic circuits of the extended amygdala can explain the fear response profile during exposure to unpredictable threat. Using fear training with predictable or unpredictable cues in mice, combined with local and cell-type-specific deficiency and rescue of cannabinoid type 1 (CB1) receptors, we found that presynaptic CB1 receptors on distinct amygdala projections to bed nucleus of the stria terminalis (BNST) are both necessary and sufficient for the shift from phasic to sustained fear in response to an unpredictable threat. These results thereby identify the causal role of a defined protein in a distinct brain pathway for the temporal development of a sustained state of anxious apprehension during unpredictability of environmental influences, reminiscent of anxiety symptoms in humans.

A comparison of high- and low-virulence Flavobacterium columnare strains reveals differences in iron acquisition components and responses to iron restriction.

Flavobacterium columnare, the causative agent of columnaris disease causes substantial mortality worldwide in numerous freshwater finfish species. Due to its global significance, an improved understanding of the factors that contribute to virulence is urgently needed. In a laboratory challenge, we found that significantly greater mortality was observed in channel catfish Ictalurus punctatus (Rafinesque) challenged with isolate LSU-066-04 (LSU) as compared to fish challenged with isolate LV-359-01 (LV). Strikingly, mortality was 100% in LSU-challenged fish, with all fish dying within the first 24 h after challenge, while mortality in the LV-challenged group was significantly lower with 26.7% of fish dying on days 1-4 post-challenge. There were no differences in initial bacterial adhesion between the isolates at 1-2 h post-challenge; however, by 4 h LSU-challenged fish had a greater bacterial load on the gill. Next, to better understand this variation in virulence, we examined transcriptional and functional attributes related to iron acquisition. The isolates were differentially sensitive to iron restriction both in vitro and in vivo and the basal expression of TonB family member genes and a ferroxidase gene differed significantly. Our findings provide new insight into iron uptake and pathogen virulence, and offer promising new targets for columnaris prevention and treatment.

Substance P excites GABAergic neurons in the mouse central amygdala through neurokinin 1 receptor activation.

Substance P (SP) is implicated in stress regulation and affective and anxiety-related behavior. Particularly high expression has been found in the main output region of the amygdala complex, the central amygdala (CE). Here we investigated the cellular mechanisms of SP in CE in vitro, taking advantage of glutamic acid decarboxylase-green fluorescent protein (GAD67-GFP) knockin mice that yield a reliable labeling of GABAergic neurons, which comprise 95% of the neuronal population in the lateral section of CE (CEl). In GFP-positive neurons within CEl, SP caused a membrane depolarization and increase in input resistance, associated with an increase in action potential firing frequency. Under voltage-clamp conditions, the SP-specific membrane current reversed at -101.5 ± 2.8 mV and displayed inwardly rectifying properties indicative of a membrane K(+) conductance. Moreover, SP responses were blocked by the neurokinin type 1 receptor (NK1R) antagonist L-822429 and mimicked by the NK1R agonist [Sar(9),Met(O2)(11)]-SP. Immunofluorescence staining confirmed localization of NK1R in GFP-positive neurons in CEl, predominantly in PKCδ-negative neurons (80%) and in few PKCδ-positive neurons (17%). Differences in SP responses were not observed between the major types of CEl neurons (late firing, regular spiking, low-threshold bursting). In addition, SP increased the frequency and amplitude of GABAergic synaptic events in CEl neurons depending on upstream spike activity. These data indicate a NK1R-mediated increase in excitability and GABAergic activity in CEl neurons, which seems to mostly involve the PKCδ-negative subpopulation. This influence can be assumed to increase reciprocal interactions between CElon and CEloff pathways, thereby boosting the medial CE (CEm) output pathway and contributing to the anxiogenic-like action of SP in the amygdala.

Heterosynaptic long-term potentiation at interneuron-principal neuron synapses in the amygdala requires nitric oxide signalling.

Long-lasting changes of synaptic efficacy are thought to be a prerequisite for memory formation and maintenance. In the basolateral complex of the amygdala (BLA), one of the main regions for fear and extinction learning of the brain, various forms of long-term potentiation (LTP) have been described for excitatory glutamatergic synapses. In contrast, little is known about the mechanisms of LTP at inhibitory GABAergic synapses. Here we provide evidence that (1) LTP at inhibitory GABAergic synapses (LTP(i)) between inhibitory interneurons and principal neurons (PNs) can be induced by theta-burst stimulation (TBS), (2) this LTP(i) is prevented by AMPA- or NMDA-receptor antagonists, and (3) this LTP(i) is abolished by the NO synthase (NOS) inhibitor L-NAME or the NO scavenger PTIO, and thus is critically dependent on nitric oxide (NO) signalling. These findings are corroborated by immunocytochemical stainings for neuronal (n) NOS, which revealed the existence of nNOS-positive neurons and fibres in the BLA. We conclude that LTP of GABAergic synaptic transmission to PNs is induced by activation of AMPA and NMDA receptors at glutamatergic synapses and subsequent retrograde NO signalling to enhance GABAergic transmission. This form of LTP at GABAergic synapses comprises a novel form of heterosynaptic plasticity within the BLA, apt to shape conditioned fear responses.

Project UJIMA: working together to make things right.

OBJECTIVE: The purpose of this paper is to describe a group of pediatric patients who utilize services of Project UJIMA, a collaborative, community-based violence intervention/prevention program serving the greater Milwaukee metropolitan area. Program goals are to (1) reduce the rates of re-injury and premature death; and (2) minimize adverse psychological consequences of violence. METHODS: Retrospective observation of 218 patients who presented to an urban pediatric Emergency Department in 1998 as a result of interpersonal violent injury and received some level of service from Project UJIMA. RESULTS: Patient age ranged from 10 to 18 years with an average of 15 years. Sixty-nine percent (69%) of patients were male. The majority of patients were African-American (69%), followed by caucasian (21%), and Latino (8%). Physical assault was the leading type of injury (62%). Nearly one-third of cases were due to firearms (31%). Three youths required a repeat ED visit due to interpersonal injury. One hundred fifty-six (72%) were referred for mental health services to address adverse psychological effects. CONCLUSION: Project UJIMA is approaching its goals of (1) reducing injury recidivism rates in this population; and (2) providing services to address related mental health issues.

Violence and associated high-risk health behavior in adolescents. Substance abuse, sexually transmitted diseases, and pregnancy of adolescents.

The intricate relationship between the social and health behaviors of persons of all ages has long been described. In adolescent health care, the risk-taking behaviors that are recognized in the areas of sexuality, drug and alcohol abuse, and violence need to be addressed. This article discusses adolescent risk behaviors and their relationships to violence. Health care providers need to consider these risk behaviors as they care for adolescents.

PIP: High-risk health behaviors in adolescents such as alcohol, tobacco, and drug use, early onset of sexual behavior, STDs, and early parenthood have been linked with violence. Analysis of the 1991 Youth Risk Behavior Survey revealed that adolescents who were using alcohol were twice as likely to carry weapons or engage in fights compared to non-alcohol users. In a study of male youth offenders accused of violent crimes, 88% admitted weekly alcohol intoxication. A survey conducted on 10,645 youths age 12-21 years regarding risk-taking behaviors also established a significant association between violent behavior and cigarette smoking although it could not determine the sequence of events in connection with smoking and violence. Furthermore, a 1995 survey of high school students in the US reported that 42% had used marijuana in their lifetime while 7% had tried cocaine at some time in their life. The 1991 Youth Risk Behavior Survey (n = 12,272) also revealed that the rate of weapon-carrying increased with the use of marijuana (48% vs. 22%, P 0.001) and the use of cocaine (71% vs. 25%, P 0.001). 63% of marijuana users and 74% of cocaine users reported physical fighting. The same survey when conducted in 1995 showed that 53% of high school students had had sexual intercourse at some time in their life, 17% had had 4 or more sexual partners, and 7% reported having been pregnant or impregnated someone else. Another study reported the influence of drugs and alcohol on unwanted sexual experiences among high school students. Having described the interrelationship of high-risk health behaviors and violence, the author urges health-care providers to develop skills that will adequately assess adolescents for these risk factors so that appropriate treatment can be provided.

False-positive preliminary radiograph interpretations in a pediatric emergency department: clinical and economic impact.

A prospective, case control study at a university-affiliated, academic pediatric emergency department was undertaken to determine the clinical impact and cost of false-positive preliminary radiograph interpretations and to compare the cost of false-positive interpretations with the estimated cost of a 24-hour on-site pediatric radiologist. Data were collected on all patients undergoing radiography of the chest, abdomen, lateral (soft tissue) neck, cervical spine, or extremities during a 5-month period. A total of 1,471 radiograph examinations was performed, and 200 (14%) misinterpretations (false-positive and false-negative) by the pediatric emergency medicine physicians were identified. As reported previously, 20 (10%) of the false-negative interpretations were noted to be clinically significant, in the current analysis, 103 (7%) false-positive radiograph interpretations were identified. False-positive interpretations were noted more frequently (14%) for soft tissue lateral neck radiographs than for any other radiograph type. Of the 103 total false-positive radiographs, nine (0.6%) resulted in an increased patient cost totaling $764.75. These data show that false-positive radiograph interpretations have limited economic and clinical impact.

Clinical impact of radiograph misinterpretation in a pediatric ED and the effect of physician training level.

Radiograph interpretation in the pediatric emergency department (ED) is commonly performed by pediatric emergency medicine (PEM) attendings or physicians-in-training. This study examines the effect of physician training level on radiograph interpretation and the clinical impact of false-negative radiograph interpretations. Data were collected on 1,471 radiographs of the chest, abdomen, extremity, lateral neck, and cervical spine interpreted by PEM attendings, one PEM fellow, one physician assistant, and emergency medicine, pediatric and family practice residents. Two hundred radiographs (14%) were misinterpreted, including 141 chest (16%), 24 extremity (8%), 20 abdomen (12%), 14 lateral neck (18%), and 1 cervical spine radiograph (2%). Physicians-in-training misinterpreted 16% of their radiographs versus 11% for PEM attendings (P = .01). Twenty (1.4%) radiographs had clinically significant (false-negative) misinterpretations, including 1.7% of physician-in-training and 0.8% of attending interpretations (P = 0.15). No morbidity resulted from the delay in correct interpretation. Radiograph misinterpretation by ED physicians occurs but is unlikely to result in significant morbidity.