CRF release from a unique subpopulation of accumbal neurons constrains action-outcome acquisition in reward learning.

Background: The nucleus accumbens (NAc) mediates reward learning and motivation. Despite an abundance of neuropeptides, peptidergic neurotransmission from the NAc has not been integrated into current models of reward learning. The existence of a sparse population of neurons containing corticotropin releasing factor (CRF) has been previously documented. Here we provide a comprehensive analysis of their identity and functional role in shaping reward learning. Methods: To do this, we took a multidisciplinary approach that included florescent in situ hybridization (N mice ≥ 3), tract tracing (N mice = 5), ex vivo electrophysiology (N cells ≥ 30), in vivo calcium imaging with fiber photometry (N mice ≥ 4) and use of viral strategies in transgenic lines to selectively delete CRF peptide from NAc neurons (N mice ≥ 4). Behaviors used were instrumental learning, sucrose preference and spontaneous exploration in an open field. Results: Here we show that the vast majority of NAc CRF-containing (NAc CRF ) neurons are spiny projection neurons (SPNs) comprised of dopamine D1-, D2- or D1/D2-containing SPNs that primarily project and connect to the ventral pallidum and to a lesser extent the ventral midbrain. As a population, they display mature and immature SPN firing properties. We demonstrate that NAc CRF neurons track reward outcomes during operant reward learning and that CRF release from these neurons acts to constrain initial acquisition of action-outcome learning, and at the same time facilitates flexibility in the face of changing contingencies. Conclusion: We conclude that CRF release from this sparse population of SPNs is critical for reward learning under normal conditions.

Thoracic positron emission tomography: 18F-fluorodeoxyglucose and beyond.

Ongoing technologic and therapeutic advancements in medicine are now testing the limits of conventional anatomic imaging techniques. The ability to image physiology, rather than simply anatomy, is critical in the management of multiple disease processes, especially in oncology. Nuclear medicine has assumed a leading role in detecting, diagnosing, staging and assessing treatment response of various pathologic entities, and appears well positioned to do so into the future. When combined with computed tomography (CT) or magnetic resonance imaging (MRI), positron emission tomography (PET) has become the sine quo non technique of evaluating most solid tumors especially in the thorax. PET/CT serves as a key imaging modality in the initial evaluation of pulmonary nodules, often obviating the need for more invasive testing. PET/CT is essential to staging and restaging in bronchogenic carcinoma and offers key physiologic information with regard to treatment response. A more recent development, PET/MRI, shows promise in several specific lung cancer applications as well. Additional recent advancements in the field have allowed PET to expand beyond imaging with 18F-flurodeoxyglucose (FDG) alone, now with the ability to specifically image certain types of cell surface receptors. In the thorax this predominantly includes 68Ga-DOTATATE which targets the somatostatin receptors abundantly expressed in neuroendocrine tumors, including bronchial carcinoid. This receptor targeted imaging technique permits targeting these tumors with therapeutic analogues such as 177Lu labeled DOTATATE. Overall, the proper utilization of PET in the thorax has the ability to directly impact and improve patient care.

Assessment of the impact of EHR heterogeneity for clinical research through a case study of silent brain infarction.

BACKGROUND: The rapid adoption of electronic health records (EHRs) holds great promise for advancing medicine through practice-based knowledge discovery. However, the validity of EHR-based clinical research is questionable due to poor research reproducibility caused by the heterogeneity and complexity of healthcare institutions and EHR systems, the cross-disciplinary nature of the research team, and the lack of standard processes and best practices for conducting EHR-based clinical research. METHOD: We developed a data abstraction framework to standardize the process for multi-site EHR-based clinical studies aiming to enhance research reproducibility. The framework was implemented for a multi-site EHR-based research project, the ESPRESSO project, with the goal to identify individuals with silent brain infarctions (SBI) at Tufts Medical Center (TMC) and Mayo Clinic. The heterogeneity of healthcare institutions, EHR systems, documentation, and process variation in case identification was assessed quantitatively and qualitatively. RESULT: We discovered a significant variation in the patient populations, neuroimaging reporting, EHR systems, and abstraction processes across the two sites. The prevalence of SBI for patients over age 50 for TMC and Mayo is 7.4 and 12.5% respectively. There is a variation regarding neuroimaging reporting where TMC are lengthy, standardized and descriptive while Mayo's reports are short and definitive with more textual variations. Furthermore, differences in the EHR system, technology infrastructure, and data collection process were identified. CONCLUSION: The implementation of the framework identified the institutional and process variations and the heterogeneity of EHRs across the sites participating in the case study. The experiment demonstrates the necessity to have a standardized process for data abstraction when conducting EHR-based clinical studies.

Pitfalls of a Mixed Metabolic Response at PET/CT.

Although the term mixed metabolic response is commonly used in PET/CT reports, it should be a red flag to reconsider the assumptions made by the PET scan reader. Fluorine 18 fluorodeoxyglucose (FDG) PET/CT is recognized as an accurate imaging method for detecting response to cancer therapies. Critical clinical decisions regarding therapy are dependent on accurate interpretation of findings. The use of standardized terminology for response assessment, such as that in the Positron Emission Tomography Response Criteria in Solid Tumors (PERCIST), is highly recommended. With PERCIST, treatment response is categorized as complete metabolic response, partial metabolic response, stable metabolic disease, or progressive metabolic disease. Mixed metabolic response is not included in PERCIST. Rather, it is used colloquially to describe a scenario in which scanning performed after systemic cancer therapy reveals divergent findings, with some tumor foci responding and others not responding or even seen progressing. In PERCIST, mixed metabolic response should be described as stable metabolic disease or progressive metabolic disease. However, the PET/CT reader may also wish to suggest that individual tumors have heterogeneous genetic and/or other characteristics and consequently a mixed response to therapy. The concept of tumor heterogeneity is gaining momentum in cancer research and thus possibly leading to options for therapy targeted to oligometastases that are not responding. However, the authors suggest exercising extreme caution when PET/CT findings appear at first to reflect what some might call a mixed response. In addition, they have found that FDG PET/CT findings are often confounding owing to the simultaneous presence of two or more unrelated disease processes. Common examples include synchronous neoplasms, inflammatory processes, and treatment-related effects. Thus, an apparent mixed response is a red flag to reconsider whether all of the FDG-avid findings are actually metastases of the same cancer. Common mimics of a mixed metabolic response that do not represent true tumor heterogeneity are highlighted to improve the FDG PET/CT reader's recognition of these lesions.©RSNA, 2019.

Natural Language Processing for the Identification of Silent Brain Infarcts From Neuroimaging Reports.

BACKGROUND: Silent brain infarction (SBI) is defined as the presence of 1 or more brain lesions, presumed to be because of vascular occlusion, found by neuroimaging (magnetic resonance imaging or computed tomography) in patients without clinical manifestations of stroke. It is more common than stroke and can be detected in 20% of healthy elderly people. Early detection of SBI may mitigate the risk of stroke by offering preventative treatment plans. Natural language processing (NLP) techniques offer an opportunity to systematically identify SBI cases from electronic health records (EHRs) by extracting, normalizing, and classifying SBI-related incidental findings interpreted by radiologists from neuroimaging reports. OBJECTIVE: This study aimed to develop NLP systems to determine individuals with incidentally discovered SBIs from neuroimaging reports at 2 sites: Mayo Clinic and Tufts Medical Center. METHODS: Both rule-based and machine learning approaches were adopted in developing the NLP system. The rule-based system was implemented using the open source NLP pipeline MedTagger, developed by Mayo Clinic. Features for rule-based systems, including significant words and patterns related to SBI, were generated using pointwise mutual information. The machine learning models adopted convolutional neural network (CNN), random forest, support vector machine, and logistic regression. The performance of the NLP algorithm was compared with a manually created gold standard. The gold standard dataset includes 1000 radiology reports randomly retrieved from the 2 study sites (Mayo and Tufts) corresponding to patients with no prior or current diagnosis of stroke or dementia. 400 out of the 1000 reports were randomly sampled and double read to determine interannotator agreements. The gold standard dataset was equally split to 3 subsets for training, developing, and testing. RESULTS: Among the 400 reports selected to determine interannotator agreement, 5 reports were removed due to invalid scan types. The interannotator agreements across Mayo and Tufts neuroimaging reports were 0.87 and 0.91, respectively. The rule-based system yielded the best performance of predicting SBI with an accuracy, sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of 0.991, 0.925, 1.000, 1.000, and 0.990, respectively. The CNN achieved the best score on predicting white matter disease (WMD) with an accuracy, sensitivity, specificity, PPV, and NPV of 0.994, 0.994, 0.994, 0.994, and 0.994, respectively. CONCLUSIONS: We adopted a standardized data abstraction and modeling process to developed NLP techniques (rule-based and machine learning) to detect incidental SBIs and WMDs from annotated neuroimaging reports. Validation statistics suggested a high feasibility of detecting SBIs and WMDs from EHRs using NLP.

Prevalence of hyperdense paraspinal vein sign in patients with spontaneous intracranial hypotension without dural CSF leak on standard CT myelography.

PURPOSE: A recently identified and treatable cause of spontaneous intracranial hypotension (SIH) is cerebrospinal fluid (CSF)-venous fistula, and a recently described computed tomography myelogram (CTM) finding highly compatible with but not diagnostic of this entity is the hyperdense paraspinal vein sign. We aimed to retrospectively measure the prevalence of the hyperdense paraspinal vein sign on CTMs in SIH patients without dural CSF leak, in comparison with control groups. METHODS: Three CTM groups were identified: 1) SIH study group, which included dural CSF leak-negative standard CTMs performed for SIH, with early and delayed imaging; 2) Early control CTMs, which were performed for indications other than SIH, with imaging shortly after intrathecal contrast administration; 3) Delayed control CTMs, which included delayed imaging. CTMs were retrospectively reviewed for the hyperdense paraspinal vein sign by experienced neuroradiologists, blinded to the group assignment. All CTMs deemed by a single reader to be positive for the hyperdense paraspinal vein sign were independently reviewed by two additional neuroradiologists; findings were considered positive only if consensus was present among all three readers. For positive cases, noncontrast CTs and prior CTMs, if available, were reviewed for the presence of the sign. RESULTS: Seven of 101 (7%) SIH patients had contrast in a spinal/paraspinal vein consistent with the hyperdense paraspinal vein sign; no patient in either control group (total n=54) demonstrated the hyperdense paraspinal vein sign (P = 0.0463). The finding occurred only at thoracic levels. Each patient had a single level of involvement. Six (86%) occurred on the right. Four occurred in female patients (57%). The sign was seen on early images in 3 of 7 cases (43%) and on both early and delayed images in 4 of 7 cases (57%). In 2 of 7 patients (29%), a noncontrast CT covering the relevant location was available and negative for the sign. A prior CTM was available in 2 of 7 patients (29%), and in both cases the hyperdense paraspinal vein sign was also evident. CONCLUSION: The prevalence of the hyperdense paraspinal vein sign in SIH patients with dural CSF leak-negative standard CTM was 7%. As the sign was not seen in control groups, this sign is highly compatible with the presence of CSF-venous fistula. Since the CTMs were not specifically dedicated to identifying hyperdense paraspinal veins (i.e., they were not dynamic and were not preceded by digital subtraction myelography), the true prevalence of the sign may be higher. Radiologists should scrutinize conventional CTMs for this sign, especially in patients in whom a traditional dural CSF leak is not identified.

Osteolytic-variant POEMS syndrome: an uncommon presentation of "osteosclerotic" myeloma.

Polyneuropathy, organomegaly, endocrinopathy, M protein, and skin changes (POEMS) syndrome, a form of osteosclerotic myeloma, is a multisystem disease related to a monoclonal plasma cell proliferative disorder. Osseous lesions are most commonly sclerotic on radiographs and computed tomography (CT), demonstrate low T1 and T2 signal intensity on magnetic resonance imaging (MRI), and have variable degrees of avidity on positon emission tomography (PET) imaging using 18-fluorodeoxyglucose (18F-FDG). We present three cases of POEMS syndrome manifesting as osteolytic lesions with indolent features, including well-defined thin sclerotic rims, no cortical disruption or periosteal reaction, no associated soft-tissue mass, and a periarticular location, all features that could lead to misinterpretation as benign bone lesions. We also report increased T1 signal and diffuse solid enhancement of these lesions on MRI, features previously unreported. POEMS syndrome should not be discounted as a diagnostic consideration in the setting of osteolytic lesions with non-aggressive imaging characteristics on radiographs or CT, especially in the presence of other supportive clinical features.

Deciphering a neuronal circuit that mediates appetite.

Hypothalamic neurons that co-express agouti-related protein (AgRP), neuropeptide Y and γ-aminobutyric acid (GABA) are known to promote feeding and weight gain by integration of various nutritional, hormonal, and neuronal signals. Ablation of these neurons in mice leads to cessation of feeding that is accompanied by activation of Fos in most regions where they project. Previous experiments have indicated that the ensuing starvation is due to aberrant activation of the parabrachial nucleus (PBN) and it could be prevented by facilitating GABA(A) receptor signalling in the PBN within a critical adaptation period. We speculated that loss of GABA signalling from AgRP-expressing neurons (AgRP neurons) within the PBN results in unopposed excitation of the PBN, which in turn inhibits feeding. However, the source of the excitatory inputs to the PBN was unknown. Here we show that glutamatergic neurons in the nucleus tractus solitarius (NTS) and caudal serotonergic neurons control the excitability of PBN neurons and inhibit feeding. Blockade of serotonin (5-HT(3)) receptor signalling in the NTS by either the chronic administration of ondansetron or the genetic inactivation of Tph2 in caudal serotonergic neurons that project to the NTS protects against starvation when AgRP neurons are ablated. Likewise, genetic inactivation of glutamatergic signalling by the NTS onto N-methyl D-aspartate-type glutamate receptors in the PBN prevents starvation. We also show that suppressing glutamatergic output of the PBN reinstates normal appetite after AgRP neuron ablation, whereas it promotes weight gain without AgRP neuron ablation. Thus we identify the PBN as a hub that integrates signals from several brain regions to bidirectionally modulate feeding and body weight.

Nuclear factor kappa B signaling regulates neuronal morphology and cocaine reward.

Although chronic cocaine-induced changes in dendritic spines on nucleus accumbens (NAc) neurons have been correlated with behavioral sensitization, the molecular pathways governing these structural changes, and their resulting behavioral effects, are poorly understood. The transcription factor, nuclear factor kappa B (NFkappaB), is rapidly activated by diverse stimuli and regulates expression of many genes known to maintain cell structure. Therefore, we evaluated the role of NFkappaB in regulating cocaine-induced dendritic spine changes on medium spiny neurons of the NAc and the rewarding effects of cocaine. We show that chronic cocaine induces NFkappaB-dependent transcription in the NAc of NFkappaB-Lac transgenic mice. This induction of NFkappaB activity is accompanied by increased expression of several NFkappaB genes, the promoters of which show chromatin modifications after chronic cocaine exposure consistent with their transcriptional activation. To study the functional significance of this induction, we used viral-mediated gene transfer to express either a constitutively active or dominant-negative mutant of Inhibitor of kappa B kinase (IKKca or IKKdn), which normally activates NFkappaB signaling, in the NAc. We found that activation of NFkappaB by IKKca increases the number of dendritic spines on NAc neurons, whereas inhibition of NFkappaB by IKKdn decreases basal dendritic spine number and blocks the increase in dendritic spines after chronic cocaine. Moreover, inhibition of NFkappaB blocks the rewarding effects of cocaine and the ability of previous cocaine exposure to increase an animal's preference for cocaine. Together, these studies establish a direct role for NFkappaB pathways in the NAc to regulate structural and behavioral plasticity to cocaine.

Environmental stress, psychological stress and allostatic load.

The mechanism by which chronic caregiving stress results in poor health is not well understood. The objective was to determine whether such a mechanism may be allostatic load, a novel concept specifying physiological systems that may suffer cumulative wear and tear following chronic stress, leading collectively to poor health. The study examines the association of allostatic load with environmental and psychological stress in the contexts of dementia caregiving and relinquishment of care, and is a 2-year longitudinal comparison of three groups: 80 new dementia spouse caregivers, 120 veteran caregivers, and 60 non-caregivers. Data comprised allostatic load markers and environmental and psychological stress measures. Cross-lagged analyses produced a statistically significant association between psychological stress and one allostatic load component (primary mediators). Psychological stress was a better predictor of primary mediators than environmental stress. Primary mediators rose with time for caregivers, but not for non-caregivers. A greater rise was evident for caregivers who had relinquished their role by the second year, although the level of psychological stress actually declined. Primary mediators are a key component of the relationship between allostatic load and prior stress. When allostatic load is treated as an outcome of stress, it is important to distinguish environmental and psychological stress.

Quantitative mapping of tryptophan hydroxylase-2, 5-HT1A, 5-HT1B, and serotonin transporter expression across the anteroposterior axis of the rat dorsal and median raphe nuclei.

Depression and anxiety disorders are among the leading causes of morbidity, mortality, and disability in the United States. Impaired serotonin neurotransmission appears to be a central mechanism inducing depressive and anxiety symptoms. Most serotonergic innervation of the forebrain arises from the median raphe nucleus (MRN) and dorsal raphe nucleus (DRN). The DRN displays a complex internal morphology, with distinct subregions varying across the anteroposterior (A-P) axis. However, many studies have considered the DRN as a whole or used easily confused terminology to describe position. Given the large differences in receptor expression, electrophysiological properties, and connectivity between various subregions of the DRN, it appears probable that they have distinct functional roles in the regulation of behavior. To foster uniform definitions of locations within these nuclei, we have quantitatively mapped gene expression in DRN and MRN for tryptophan hydroxylase-2 (Tph2), the serotonin transporter, as well as 5-HT1A and 5-HT1B receptors. These quantitative studies revealed differences in the density of expression of each gene in the ventromedial, dorsomedial, and dorsolateral subnuclei of the DRN, as well as distinct variation in expression across the A-P axis. These findings provide additional evidence that subregions of the DRN are heterogeneous and need to be considered independently. In addition, a fine scale map of Tph2 expression suggests definitions for categorical divisions of the DRN across the A-P axis. These are based on distinct morphological patterns of Tph2 expression and may be more reflective of physiology than the classic terminology dividing the DRN into equal thirds.

Measuring disability with parsimony: evidence for the utility of a single item.

PURPOSE: To provide evidence for the utility of a single item measure designed to quantify disability in the past 30 days. METHOD: Australian data from studies comprising a community-dwelling elderly sample (N = 328) and a sample of chronic osteoarthritis (OA) patients (N = 119) are reported. Degree of disability was classified as 0-30 days, 0 vs. 1 or more days, and 0-9 vs. 10 or more days. Associations between disability and a range of demographic, health-related, and psychological variables were assessed. RESULTS: Participants with OA reported a significantly higher level of disability than participants from the community sample regardless of how disability was classified. Modest levels of association were noted between the number of disability days (0-30) and both health and psychological indices in both samples. The three alternative classifications of disability made little difference to the significance of associations. On balance, the comparison of 0-9 vs. 10 or more days appeared the more predictive classification of disability. CONCLUSIONS: The performance of the single item measure of disability was generally very satisfactory. Future investigations into the clinical application of the item across a range of patient groups are encouraged.

Increased expression of 5-HT1B receptor in dorsal raphe nucleus decreases fear-potentiated startle in a stress dependent manner.

5-HT(1B) autoreceptors regulate serotonin release from terminals of dorsal raphe nucleus (DRN) projections. Due to postsynaptic 5-HT(1B) receptors in DRN terminal fields, it has not previously been possible to manipulate 5-HT(1B) autoreceptor activity without also changing 5-HT(1B) heteroreceptor activity. We have developed a viral gene transfer strategy to express epitope-tagged 5-HT(1B) and green fluorescent protein in vivo, allowing us to increase 5-HT(1B) expression in DRN neurons. We have shown that increased 5-HT(1B) autoreceptor expression reduced anxiety in unstressed animals but increased anxiety following inescapable stress. These findings suggest that effects of increased 5-HT(1B) autoreceptor expression are dependent on stress context. To better understand the mechanisms underlying these observations, we have used fear-potentiated startle (FPS). FPS is especially sensitive to the activity of the amygdala, which shares reciprocal connections with DRN. In the absence of an inescapable stressor, increased 5-HT(1B) autoreceptor expression attenuated FPS response compared with animals injected with a virus expressing only green fluorescent protein. Administration of the 5-HT(1B) antagonist SB224289 (5 mg/kg i.p.) before startle testing blocked the effects of increased 5-HT(1B) autoreceptor expression. Since SB224289 had no effect on FPS in the absence of viral gene transfer, these results suggest that the antagonist reversed the behavioral effects of increased 5-HT(1B) autoreceptor expression through blockade of transgenic receptors. When tested 24 h following water-restraint stress, animals with increased 5-HT(1B) autoreceptors demonstrated restoration of robust FPS response. These results extend our previous studies and suggest explanations for the complex relationship between 5-HT(1B) autoreceptor expression, stress, and anxiety behavior.

A randomized controlled trial of an education and counselling intervention for families after stroke.

OBJECTIVES: To determine whether education and counselling after stroke leads to improved family functioning and psychosocial outcomes for stroke patients and their spouses, and better functional and social outcomes for patients. DESIGN: Two-group randomized controlled trial. Data were collected on admission to and discharge from rehabilitation, and again six months later. SETTING: Rehabilitation units at Repatriation General Hospital and Griffith Hospital, in Adelaide, South Australia. PARTICIPANTS: Sixty-two stroke patients and their spouses, 32 in the intervention group and 30 in the control group. INTERVENTION: Stroke information package and three visits from a social worker trained in family counselling. OUTCOME MEASURES: Family functioning: McMaster Family Assessment Device (FAD); functional status: Barthel Index (BI); social recovery: Adelaide Activities Profile (AAP); depression: Geriatric Depression Scale (GDS); anxiety: Hospital Anxiety and Depression Scale (HADS); mastery: Mastery Scale (MS); health status: SF-36. RESULTS: At six months the intervention group had better family functioning for both patients (mean FAD difference 0.19) and spouses (mean difference 0.09). A modest benefit in functional status for intervention patients (mean BI difference 1.3) was related to improved family functioning. Intervention patients reported better social recovery (mean AAP differences: domestic chores 5.7, household maintenance 4.6, social activities 11.5), but there were no significant effects on depression, anxiety, mastery or health status. CONCLUSIONS: An education and counselling intervention maintained family functioning, and in turn led to improved functional and social patient outcomes. This approach helps patients and their spouses to make the optimal adjustment to living with stroke.

The quality of life of spouse dementia caregivers: changes associated with yielding to formal care and widowhood.

The focus of the study was the effect on spouse dementia caregivers of relinquishing care. The study used a longitudinal design, in which a group of 150 dementia caregivers were interviewed 2 years apart (designated Time 1 and Time 2), with data collected from both continuing caregivers and those who had relinquished care. The aims were to determine the extent to which changes over time in quality of life differed between continuing caregivers, those who had yielded to formal care, and those who had been widowed; and to examine whether change in quality of life variables was associated with time since yielding to formal care and time since death of the spouse. Quality of life was defined in terms of health status, psychological well-being, and activity participation. All participants were interviewed in their own homes. Three groups of participants were identified at Time 2: those who continued to provide care for their spouses (n=60); those who had yielded their caregiver role by admitting their spouses to permanent residential care (n=53); and those who had admitted their spouses to permanent institutional care, but whose spouse had then died (n=37). Different patterns of quality of life changes were observed between the three groups, with both positives and negatives associated with disengagement from the caregiving role. Positive changes were particularly evident in psychological well-being and activity participation. These findings were discussed in terms of their relevance for a life transitions approach to the relinquishment of caregiving.

Role of corticotropin-releasing factor family peptides and receptors in stress-related psychiatric disorders.

Corticotropin-releasing factor (CRF) and related neuropeptides such as urocortin are key mediators of stress in the central nervous system. Through two types of G-protein-linked receptors, they play important roles in stress and its relationship to a variety of psychiatric illnesses. CRF appears to play an important role in regulating key neural systems involved in controlling mood, anxiety, feeding behavior, and the interactions between stress and drug addiction. Our improved understanding of the actions of CRF and related peptides reveals not only mechanisms by which stress affects behavior, but also new opportunities to intervene in psychiatric disorders related to stress exposure.

Overexpression of 5-HT1B receptor in dorsal raphe nucleus using Herpes Simplex Virus gene transfer increases anxiety behavior after inescapable stress.

5-HT(1B) autoreceptors have been implicated in animal models of stress and are regulated selectively by serotonin-selective reuptake inhibitors such as fluoxetine. These terminal autoreceptors regulate serotonin release from dorsal raphe nucleus (DRN) projections throughout rat forebrain. However, it has not been previously possible to manipulate 5-HT(1B) autoreceptor activity selectively without also changing 5-HT(1B) activity in other neurons mediating different behavioral responses. Therefore, we have developed a viral-mediated gene transfer strategy to express hemagglutinin-tagged 5-HT(1B) and manipulate these autoreceptors in DRN. Green fluorescent protein (GFP) was coexpressed from a separate transcriptional unit on the same amplicon to assist in monitoring infection and expression. We confirmed the expression and biological activity of both transgenic proteins in vitro. When injected directly into DRN using stereotaxic procedure, HA-5-HT(1B) receptors were expressed in serotonergic neurons and translocated to the forebrain. The effect of DRN expression of HA-5-HT(1B) on stress-induced behaviors was compared with control rats that received GFP-only amplicons. There was no change in immobility in the forced swim test. However, HA-5-HT(1B) expression significantly reduced entrances into the central region of an open-field arena after water-restraint stress without altering overall locomotor activity, but not in the absence of stress exposure. HA-5-HT(1B) expression also reduced entries into the open arms of the elevated plus maze after water restraint. Because these tests are sensitive to increases in anxiety-like behavior, our results suggest that overactivity of 5-HT(1B) autoreceptors in DRN neurons may be an important mediator of pathological responses to stressful events.