Modulatory effects of norepinephrine, acting on alpha 1 receptors in the central nucleus of the amygdala, on behavioral and neuroendocrine responses to acute immobilization stress

An overview of the pathophysiology of agitation in Alzheimer's dementia with a focus on neurotransmitters and circuits

Alzheimer's dementia (AD) is a progressive, neurodegenerative disease often accompanied by neuropsychiatric symptoms that profoundly impact both patients and caregivers. Agitation is among the most prevalent and distressing of these symptoms and often requires treatment. Appropriate therapeutic interventions depend on understanding the biological basis of agitation and how it may be affected by treatment. This narrative review discusses a proposed pathophysiology of agitation in Alzheimer's dementia based on convergent evidence across research approaches. Available data indicate that agitation in Alzheimer's dementia is associated with an imbalance of activity between key prefrontal and subcortical brain regions. The monoamine neurotransmitter systems serve as key modulators of activity within these brain regions and circuits and are rendered abnormal in AD. Patients with AD who exhibited agitation symptoms during life have alterations in neurotransmitter nuclei and related systems when the brain is examined at autopsy. The authors present a model of agitation in Alzheimer's dementia in which noradrenergic hyperactivity along with serotonergic deficits and dysregulated striatal dopamine release contribute to agitated and aggressive behaviors.

Role of the locus coeruleus-noradrenergic system in stress-related psychopathology and resilience: Clinical and pre-clinical evidences

Stressful events, from daily stressors to traumatic experiences, are common and occur at any age. Despite the high prevalence of trauma, not everyone develops stress-related disorders like major depressive disorder (MDD) and post-traumatic stress disorder (PTSD), a variation attributed to resilience, the ability to adapt and avoid negative consequences of significant stress. This review examines the locus coeruleus-norepinephrine (LC-NE) system, a critical component in the brain's stress response. It discusses the LC-NE system's anatomical and functional complexity and its role in individual variability in stress responses. How different etiological factors and stress modalities affect the LC-NE system, influencing both adaptive stress responses and psychopathologies, are discussed and supported by evidence from human and animal studies. It also explores molecular and cellular adaptations in the LC that contribute to resilience, including roles of neuropeptide, inflammatory cytokines, and genetic modulation, and addresses developmental and sex differences in stress vulnerability. The need for a multifaceted approach to understand stress-induced psychopathologies is emphasized and pave the way for more personalized interventions for stress-related disorders.

Epinephrine injected into the basolateral amygdala affects anxiety-like behavior and memory performance in stressed rats

The amygdala is known to mediate in moderating the impacts of emotional arousal and stress on memory. According to a growing body of research, the basolateral amygdala (BLA) is an important locus for integrating neuromodulator influences coordinating the retrieval of different types of memory and anxiety. This study aimed to investigate how the epinephrine in the BLA affects hippocampal fear memory, anxiety, and plasticity in control and stressed rats. For four days, male Wistar rats were exposed to electrical foot-shock stress. Animals received bilateral micro-injections of either vehicle or epinephrine (1 µg/side) into the BLA over four days (5 min before foot-shock stress). Behavioral characteristics (fear memory and anxiety-like behavior), histological features and electrophysiological parameters were investigated. Epinephrine injection into BLA resulted in a considerable impairment of fear memory in stressed rats. On the other hand, epinephrine effectively affected fear memory in control rats. Under stress conditions, epinephrine in the BLA is thought to increase anxiety-like behaviors. Treatment with epinephrine significantly increases the slope of fEPSP in the CA1 region of the hippocampus in the control and stress rats. In different groups, foot-shock stress had no effect on the apical and basal dendritic length in the CA1 region of the hippocampus. These results indicate that activating adrenergic receptors diminish fear memory and anxiety-like behaviors in the foot-shock stress, which this impact is independent of CA1 long-term potentiation induction.

Adrenocortical and autonomic cross-system regulation in youth: A meta-analysis

Childhood and adolescence are salient periods for the development of adrenocortical and autonomic arms of the stress response system (SRS), setting the stage for subsequent health and adaptive functioning. Although adrenocortical and autonomic systems theoretically function in highly coordinated ways, the strength of the relationship between these systems remains unclear. We leveraged a multivariate mixed effects meta-analytic approach to assess associations between adrenocortical, sympathetic, and parasympathetic functioning at rest and reactivity during stress-inducing tasks across 52 studies (N = 7,671; 5-20 years old). Results suggested a modest positive relation between adrenocortical and sympathetic systems as well as between adrenocortical and parasympathetic systems. Moderation analyses indicated the strength of associations varied as a function of several methodological and sociodemographic characteristics. Environmental effects on cross-system regulation were less clear, perhaps due to underrepresentation of adverse-exposed youth in the included studies. Collectively, our findings call for greater methodological attention to the dynamical, non-linear nature of cross-system functioning, as well as the role of experience in their organization across development.

An ensemble recruited by α2a-adrenergic receptors is engaged in a stressor-specific manner in mice

α2a-adrenergic receptor (α2a-AR) agonists are candidate substance use disorder therapeutics due to their ability to recruit noradrenergic autoreceptors to dampen stress system engagement. However, we recently found that postsynaptic α2a-ARs are required for stress-induced reinstatement of cocaine-conditioned behavior. Understanding the ensembles recruited by these postsynaptic receptors (heteroceptors) is necessary to understand noradrenergic circuit control. We utilized a variety of approaches in FosTRAP (Targeted Recombination in Active Populations) mice to define an ensemble of cells activated by the α2a-AR partial agonist guanfacine ("Guansembles") in the bed nucleus of the stria terminalis (BST/BNST), a region key to stress-induced reinstatement of drug seeking. We define BNST "Guansembles" and show they differ from restraint stress-activated cells. Guanfacine produced inhibition of cAMP-dependent signaling in Guansembles, while chronic restraint stress increased cAMP-dependent signaling. Guanfacine both excited and inhibited aspects of Guansemble neuronal activity. Further, while some stressors produced overall reductions in Guansemble activity, active coping events during restraint stress and exposure to unexpected shocks were both associated with Guansemble recruitment. Using viral tracing, we define a BNST Guansemble afferent network that includes regions involved in the interplay of stress and homeostatic functions. Finally, we show that activation of Guansembles produces alterations in behavior on the elevated plus maze consistent with task-specific anxiety-like behavior. Overall, we define a population of BNST neurons recruited by α2a-AR signaling that opposes the behavioral action of canonical autoreceptor α2a-AR populations and which are differentially recruited by distinct stressors. Moreover, we demonstrate stressor-specific physiological responses in a specific neuronal population.

Comparative evaluation of natural neuroprotectives and their combinations on chronic immobilization stress-induced depression in experimental mice

The present study evaluates the potential of neuroprotective phytochemicals-rutin (R), resveratrol (Res), 17β-estradiol (17β-E2), and their different combinations against chronic immobilization stress (CIS)-induced depression-like behaviour in male albino mice. Here, the mice were exposed to stress via immobilization of their four limbs under a restrainer for 6 h daily until 7 days of the induction after 30 min of respective drug treatment in different mice groups. The result found the protective effect of these phytoconstituents and their combinations against CIS-induced depression due to their ability to suppress oxidative stress, restore mitochondria, HPA-axis modulation, neurotransmitter level, stress hormones, and inflammatory markers. Also, the combination drug regimens of these phytoconstituents showed synergistic results in managing the physiological and biochemical features of depression. Thus, these neuroprotective could be utilized well in combination to manage depression-like symptoms during episodic stress. Furthermore, such results could be well justified when administered in polyherbal formulation with these neuroprotective as major components. In addition, an advanced study can be designed at the molecular and epigenetics level using a formulation based on these neuroprotective.

Lateral Septum Somatostatin Neurons are Activated by Diverse Stressors

The lateral septum (LS) is a forebrain structure that has been implicated in a wide range of behavioral and physiological responses to stress. However, the specific populations of neurons in the LS that mediate stress responses remain incompletely understood. Here, we show that neurons in the dorsal lateral septum (LSd) that express the somatostatin gene (hereafter, LSd^Sst neurons) are activated by diverse stressors. Retrograde tracing from LSd^Sst neurons revealed that these neurons are directly innervated by neurons in the locus coeruleus (LC), the primary source of norepinephrine well-known to mediate diverse stress-related functions in the brain. Consistently, we found that norepinephrine increased excitatory synaptic transmission onto LSd^Sst neurons, suggesting the functional connectivity between LSd^Sst neurons and LC noradrenergic neurons. However, optogenetic stimulation of LSd^Sst neurons did not affect stress-related behaviors or autonomic functions, likely owing to the functional heterogeneity within this population. Together, our findings show that LSd^Sst neurons are activated by diverse stressors and suggest that norepinephrine released from the LC may modulate the activity of LSd^Sst neurons under stressful circumstances.

A balancing act: the role of pro- and anti-stress peptides within the central amygdala in anxiety and alcohol use disorders

The central nucleus of the amygdala (CeA) is widely implicated as a structure that integrates both appetitive and aversive stimuli. While intrinsic CeA microcircuits primarily consist of GABAergic neurons that regulate amygdala output, a notable feature of the CeA is the heterogeneity of neuropeptides and neuropeptide/neuromodulator receptors that it expresses. There is growing interest in the role of the CeA in mediating psychopathologies, including stress and anxiety states and their interactions with alcohol use disorders. Within the CeA, neuropeptides and neuromodulators often exert pro- or anti- stress actions, which can influence anxiety and alcohol associated behaviours. In turn, alcohol use can cause adaptions within the CeA, which may render an individual more vulnerable to stress which is a major trigger of relapse to alcohol seeking. This review examines the neurocircuitry, neurochemical phenotypes and how pro- and anti-stress peptide systems act within the CeA to regulate anxiety and alcohol seeking, focusing on preclinical observations from animal models. Furthermore, literature exploring the targeting of genetically defined populations or neuronal ensembles and the role of the CeA in mediating sex differences in stress x alcohol interactions are explored.

The α1-adrenergic receptors in the amygdala regulate the induction of learned despair through protein kinase C-beta signaling

Hyperactivity of amygdala is observed in patients with major depressive disorder. Although the role of α1-adrenoceptor in amygdala on fear memory has been well studied, the role of α1-adrenoceptor in amygdala on depression-like behaviors remains unclear. Therefore, we investigated the effect of α1A-adrenoreceptor in amygdala on despair behavior, evaluated by the immobility time during tail suspension test (TST), pharmacological intervention, and immunohistological methods. C57BL6/J mice given a bilateral intra-amygdala injection of artificial cerebrospinal fluid exhibited an increased duration of immobility in the latter half of both trials of TST with a 24-h interval, a phenomenon known as learned despair. Intra-amygdala injection of WB4101 (1.7 nmol/0.1 µl), an α1 adrenoreceptor antagonist, but not propranolol (250 pmol/0.1 µl), a β-adrenoreceptor antagonist, blocked the induction of learned despair during TST. Immunostaining experiments revealed that ~61-75% of α1A-adrenoreceptor-positive neurons were colocalized with GAD65/67 in amygdala, implying that the α1-adrenoceptors in amygdala may enormously regulate the GABA release. Protein kinase C-beta (PKCβ) was predominantly expressed in the α1A-adrenoreceptor-positive neurons in the BLA, whereas protein kinase C-epsilon (PKCε) was highly expressed with the α1A-adrenoreceptor in the Central nucleus of amygdala. Intra-amygdala injection of ruboxistaurin (10 pmol/0.1 µl), a PKCβ inhibitor, blocked the induction of learned despair during TST, whereas neither TAT-εV1-2 (500 ng/0.1 μl), a cell-permeant PKCε inhibitory peptide, nor HBDDE (50 pmol/0.1 µl), an inhibitor of PKCα and -γ, affected the duration of immobility during TST. These data suggest that the α1-adrenoreceptor in amygdala regulates the induction of learned despair via PKCβ.

Preclinical characterization of ACH-000029, a novel anxiolytic compound acting on serotonergic and alpha-adrenergic receptors

Anxiety disorders are serious and common mental diseases, yet there is still a need for the development of more effective anxiolytics with better safety profiles than benzodiazepines and serotonin reuptake inhibitors. The serotonergic and noradrenergic systems have reciprocal interactions and are intricately related to the pathogenesis of anxiety. In this study, the anxiolytic-like effect of the novel compound ACH-000029, 3-(2-(4-(2-methoxyphenyl) piperazine-1-yl) ethyl) quinazoline-4(3H)-one, is reported. This compound acts at selected serotonergic (5-HT1A and 5-HT1D partial agonism and 5-HT2A antagonism) and α-adrenergic (α-1A, 1B and 1D antagonism) receptors, with good selectivity over other G-protein-coupled receptors. ACH-000029 exhibited high blood-brain barrier permeation and acute anxiolytic effects in the marble burying (MB) and light-dark box (LDB) models of anxiety over the dose ranges of 8-32 mg/kg i.p. and 16-30 mg/kg p.o. The anxiolytic activity was comparable to that observed for serotonin reuptake inhibitors (paroxetine and fluoxetine) and benzodiazepines (alprazolam, diazepam and clobazam). The analysis of the whole-brain c-fos expression following oral dosing showed that ACH-000029 regulated regions highly associated with the processing of environmental stimuli and anxiety behavior, such as the amygdala, paraventricular nucleus of the thalamus, retrosplenial dorsal, pallidum, bed nuclei of the stria terminalis, and locus ceruleus. No safety concerns were identified for ACH-000029 in the functional observational battery up to 50 mg/kg i.p. and in the nonprecipitated withdrawal test up to 30 mg/kg p.o. twice daily for 20 days. This work supports the further development of ACH-000029 as a drug candidate for the treatment of anxiety disorders. The analysis of the in vitro pharmacology and brain regions regulated by this compound may also lead to the exploration of other indications within the psychiatry field.

Genetic identification of a population of noradrenergic neurons implicated in attenuation of stress-related responses

Noradrenergic signaling plays a well-established role in promoting the stress response. Here we identify a subpopulation of noradrenergic neurons, defined by developmental expression of Hoxb1, that has a unique role in modulating stress-related behavior. Using an intersectional chemogenetic strategy, in combination with behavioral and physiological analyses, we show that activation of Hoxb1-noradrenergic (Hoxb1-NE) neurons decreases anxiety-like behavior and promotes an active coping strategy in response to acute stressors. In addition, we use cerebral blood volume-weighted functional magnetic resonance imaging to show that chemoactivation of Hoxb1-NE neurons results in reduced activity in stress-related brain regions, including the bed nucleus of the stria terminalis, amygdala, and locus coeruleus. Thus, the actions of Hoxb1-NE neurons are distinct from the well-documented functions of the locus coeruleus in promoting the stress response, demonstrating that the noradrenergic system contains multiple functionally distinct subpopulations.

Ventral hippocampal overexpression of Cannabinoid Receptor Interacting Protein 1 (CNRIP1) produces a schizophrenia-like phenotype in the rat

Adolescent cannabis use has been implicated as a risk factor for schizophrenia; however, it is neither necessary nor sufficient. Previous studies examining this association have focused primarily on the role of the cannabinoid receptor 1 (CB1R) with relatively little known about a key regulatory protein, the cannabinoid receptor interacting protein 1 (CNRIP1). CNRIP1 is an intracellular protein that interacts with the C-terminal tail of CB1R and regulates its intrinsic activity. Previous studies have demonstrated aberrant CNRIP1 DNA promoter methylation in post-mortem in human patients with schizophrenia, and we have recently reported decreased methylation of the CNRIP1 DNA promoter in the ventral hippocampus (vHipp) of a rodent model of schizophrenia susceptibility. To examine whether augmented CNRIP1 expression could contribute to the pathology of schizophrenia, we performed viral-mediated overexpression of CNRIP1 in the vHipp of Sprague Dawley rats. We then tested these rats for behavioral correlates of schizophrenia symptoms, followed by electrophysiology to determine the effects on the dopamine system, known to underlie psychosis. Here, we report that overexpression of vHipp CNRIP1 induces impairments in latent inhibition and social interaction, similar to those observed in individuals with schizophrenia and in rodent models of the disease. Furthermore, rats overexpressing vHipp CNRIP1 displayed a significant increase in ventral tegmental area (VTA) dopamine neuron population activity, a putative correlate of psychosis. These data provide evidence that alterations in CNRIP1 may contribute to the pathophysiology of schizophrenia, as overexpression is sufficient to produce neurophysiological and behavioral correlates consistently observed in rodent models of the disease.

Biobehavioral Interactions Between Stress and Alcohol

In this review, the effects of stress on alcohol drinking are discussed. The interactions between biological stress systems and alcohol drinking are examined, with a focus on the hypothalamic pituitary adrenal axis, corticotropin releasing factor, dynorphin, neuropeptide Y, and norepinephrine systems. Findings from animal models suggest that these biological stress systems may be useful targets for medications development for alcohol use disorder and co-occurring stress-related disorders in humans.

Uncovering the neural circuitry involved in the stress-attenuation effects of chewing

Previous animal studies have indicated that coupling restraint stress load with activation of the masticatory organs (chewing) causes a reduction in the systemic and central nervous system stress response. However, the brain mechanism underlying this effect is unknown. Therefore, in this review, we summarize the literature regarding brain regions involved in the attenuating effects of chewing and the systemic stress response attenuation effects induced by those brain regions. In addition, we also focusing on the amygdala, as the emotional control center, and the hypothalamic-pituitary-adrenal axis, as one of the outputs of the systemic response. In particular, we will report on one of the chewing-related stress attenuation mechanisms within the brain brought about by the activation of the inhibition pathway accompanying the activation of the amygdala's GABAergic function.

Embryonic stem cell transplants as a therapeutic strategy in a rodent model of autism

Autism is a neurodevelopmental disorder characterized by disruptions in three core behavioral domains: deficits in social interaction, impairments in communication, and repetitive and stereotyped patterns of behavior or thought. There are currently no drugs available for the treatment of the core symptoms of ASD and drugs that target comorbid symptoms often have serious adverse side effects, suggesting an urgent need for new therapeutic strategies. The neurobiology of autism is complex, but converging evidence suggests that ASD involves disruptions in the inhibitory GABAergic neurotransmitter system. Specifically, people with autism have a reduction in parvalbumin (PV)-containing interneurons in the PFC, leading to the suggestion that restoring interneuron function in this region may be a novel therapeutic approach for ASD. Here we used a dual-reporter embryonic stem cell line to generate enriched populations of PV-positive interneurons, which were transplanted into the medial prefrontal cortex (mPFC) of the Poly I:C rodent model of autism. PV interneuron transplants were able to decrease pyramidal cell firing in the mPFC and alleviated deficits in social interaction and cognitive flexibility. Our results suggest that restoring PV interneuron function in the mPFC may be a novel and effective treatment strategy to reduce the core symptoms of autism.

Maternal androgen excess and obesity induce sexually dimorphic anxiety-like behavior in the offspring

Maternal polycystic ovary syndrome (PCOS), a condition associated with hyperandrogenism, is suggested to increase anxiety-like behavior in the offspring. Because PCOS is closely linked to obesity, we investigated the impact of an adverse hormonal or metabolic maternal environment and offspring obesity on anxiety in the offspring. The obese PCOS phenotype was induced by chronic high-fat-high-sucrose (HFHS) consumption together with prenatal dihydrotestosterone exposure in mouse dams. Anxiety-like behavior was assessed in adult offspring with the elevated-plus maze and open-field tests. The influence of maternal androgens and maternal and offspring diet on genes implicated in anxiety were analyzed in the amygdala and hypothalamus with real-time PCR ( n = 47). Independent of diet, female offspring exposed to maternal androgens were more anxious and displayed up-regulation of adrenoceptor α 1B in the amygdala and up-regulation of hypothalamic corticotropin-releasing hormone ( Crh). By contrast, male offspring exposed to a HFHS maternal diet had increased anxiety-like behavior and showed up-regulation of epigenetic markers in the amygdala and up-regulation of hypothalamic Crh. Overall, there were substantial sex differences in gene expression in the brain. These findings provide novel insight into how maternal androgens and obesity exert sex-specific effects on behavior and gene expression in the offspring of a PCOS mouse model.-Manti, M., Fornes, R., Qi, X., Folmerz, E., Lindén Hirschberg, A., de Castro Barbosa, T., Maliqueo, M., Benrick, A., Stener-Victorin, E. Maternal androgen excess and obesity induce sexually dimorphic anxiety-like behavior in the offspring.

Stem cell-derived interneuron transplants as a treatment for schizophrenia: preclinical validation in a rodent model

An increasing literature suggests that schizophrenia is associated with a reduction in hippocampal interneuron function. Thus, we posit that stem cell-derived interneuron transplants may be an effective therapeutic strategy to reduce hippocampal hyperactivity and attenuate behavioral deficits in schizophrenia. Here we used a dual-reporter embryonic stem cell line to generate enriched populations of parvalbumin (PV)- or somatostatin (SST)-positive interneurons, which were transplanted into the ventral hippocampus of the methylazoxymethanol rodent model of schizophrenia. These interneuron transplants integrate within the existing circuitry, reduce hippocampal hyperactivity and normalize aberrant dopamine neuron activity. Further, interneuron transplants alleviate behaviors that model negative and cognitive symptoms, including deficits in social interaction and cognitive inflexibility. Interestingly, PV- and SST-enriched transplants produced differential effects on behavior, with PV-enriched populations effectively normalizing all the behaviors examined. These data suggest that the stem cell-derived interneuron transplants may represent a novel therapeutic strategy for schizophrenia.

α2-adrenoceptor-mediated inhibition in the central amygdala blocks fear-conditioning

The central amygdala is critical for the acquisition and expression of fear memories. This region receives a dense innervation from brainstem noradrenergic cell groups and has a high level of α₂-adrenoceptor expression. Using whole-cell electrophysiological recordings from rat brain slices, we characterise the role of pre-synaptic α₂-adrenoceptor in modulating discrete inhibitory and excitatory connections within both the lateral and medial division of the central amygdala. The selective α₂-adrenoceptor agonist clonidine blocked the excitatory input from the pontine parabrachial neurons onto neurons of the lateral central amygdala. In addition, clonidine blocked inhibitory connections from the medial paracapsular intercalated cell mass onto both lateral and medial central amygdala neurons. To examine the behavioural consequence of α₂-adrenoceptor-mediated inhibition of these inputs, we infused clonidine into the central amygdala prior to contextual fear-conditioning. In contrast to vehicle-infused rats, clonidine-infused animals displayed reduced levels of freezing 24 hours after training, despite showing no difference in freezing during the training session. These results reveal a role for α₂-adrenoceptors within the central amygdala in the modulation of synaptic transmission and the formation of fear-memories. In addition, they provide further evidence for a role of the central amygdala in fear-memory formation.

Manual Acupuncture at PC6 Ameliorates Acute Restraint Stress-Induced Anxiety in Rats by Normalizing Amygdaloid Noradrenergic Response

Acupuncture improves ethanol withdrawal-induced anxiety in rats in an acupoint-dependent manner. Thus, the present study investigated the effects of acupuncture on acute restraint stress- (ARS-) induced anxiety. Male rats were exposed to ARS for 3 h followed by acupuncture at either PC6 (Neiguan), HT7 (Shenmen), or a nonacupoint (tail) once a day for three consecutive days. Five minutes after the third acupuncture treatment, anxiety-like behavior was evaluated in an elevated plus maze (EPM). Additionally, plasma corticosterone (CORT) levels were measured by radioimmunoassay and the concentrations of norepinephrine (NE) and 3-methoxy-4-hydroxy-phenylglycol (MHPG) in the central nucleus of the amygdala (CeA) were determined using high-performance liquid chromatography. Acupuncture at PC6, but not HT7 or a nonacupoint, attenuated anxiety-like behavior, but this attenuation was abolished by a postacupunctural intra-CeA infusion of NE. Acupuncture at PC6 also reduced the oversecretion of plasma CORT and inhibited increases in amygdaloid NE and MHPG induced by ARS. Further, Western blot analyses and real-time polymerase chain reaction assays revealed that acupuncture at PC6 prevented ARS-induced enhancements in the protein and mRNA expressions of tyrosine hydroxylase in the CeA. These results suggest that acupuncture performed specifically at acupoint PC6 reduces ARS-induced anxiety-like behavior by dampening amygdaloid noradrenergic responses.

Higher pretreatment blood pressure is associated with greater alcohol drinking reduction in alcohol-dependent individuals treated with doxazosin

BACKGROUND

Preclinical and clinical research suggest that the α₁ receptor antagonist prazosin reduces alcohol consumption. Furthermore, clinical studies indicate a role for prazosin in treating Post-Traumatic Stress Disorder (PTSD) symptoms and a recent trial suggested that pre-treatment blood pressure (BP) predicts therapeutic response for prazosin in PTSD patients. Whether pre-treatment BP may predict response to α₁ blockers in alcohol-dependent (AD) patients is unknown. We previously reported a randomized controlled trial (RCT) where doxazosin, an α₁ receptor antagonist with a more favorable pharmacokinetic profile than prazosin, reduced drinks per week (DPW) and heavy drinking days (HDD) in AD patients with a high family history density of alcoholism. In this study, we tested pre-treatment BP as another potentially valuable clinical moderator of doxazosin's response on alcohol consumption.

METHODS

This was a double-blind placebo-controlled RCT testing doxazosin up to 16mg/day in AD treatment-seeking patients (N=41). The hypothesized moderator effect of baseline standing systolic and diastolic BP on DPW and HDD was tested.

RESULTS

With pre-treatment standing diastolic BP as a moderator, there were significant BP x medication interactions for both DPW [**p=0.009, d=0.80] and HDD [*p=0.018, d=1.11]. Post-hoc analyses indicated significant doxazosin effects in patients with higher standing BP in reducing both DPW and HDD.

CONCLUSION

These findings suggest that higher standing diastolic BP at baseline (pre-treatment) may represent a predictor of doxazosin's response on alcohol consumption in AD patients. These results further elucidate the possible efficacy and mechanisms of action of α₁ receptor antagonism in AD individuals.

Acute Stress Suppresses Synaptic Inhibition and Increases Anxiety via Endocannabinoid Release in the Basolateral Amygdala

Stress and glucocorticoids stimulate the rapid mobilization of endocannabinoids in the basolateral amygdala (BLA). Cannabinoid receptors in the BLA contribute to anxiogenesis and fear-memory formation. We tested for rapid glucocorticoid-induced endocannabinoid regulation of synaptic inhibition in the rat BLA. Glucocorticoid application to amygdala slices elicited a rapid, nonreversible suppression of spontaneous, but not evoked, GABAergic synaptic currents in BLA principal neurons; the effect was also seen with a membrane-impermeant glucocorticoid, but not with intracellular glucocorticoid application, implicating a membrane-associated glucocorticoid receptor. The glucocorticoid suppression of GABA currents was not blocked by antagonists of nuclear corticosteroid receptors, or by inhibitors of gene transcription or protein synthesis, but was blocked by inhibiting postsynaptic G-protein activity, suggesting a postsynaptic nongenomic steroid signaling mechanism that stimulates the release of a retrograde messenger. The rapid glucocorticoid-induced suppression of inhibition was prevented by blocking CB1 receptors and 2-arachidonoylglycerol (2-AG) synthesis, and it was mimicked and occluded by CB1 receptor agonists, indicating it was mediated by the retrograde release of the endocannabinoid 2-AG. The rapid glucocorticoid effect in BLA neurons in vitro was occluded by prior in vivo acute stress-induced, or prior in vitro glucocorticoid-induced, release of endocannabinoid. Acute stress also caused an increase in anxiety-like behavior that was attenuated by blocking CB1 receptor activation and inhibiting 2-AG synthesis in the BLA. Together, these findings suggest that acute stress causes a long-lasting suppression of synaptic inhibition in BLA neurons via a membrane glucocorticoid receptor-induced release of 2-AG at GABA synapses, which contributes to stress-induced anxiogenesis.

SIGNIFICANCE STATEMENT

We provide a cellular mechanism in the basolateral amygdala (BLA) for the rapid stress regulation of anxiogenesis in rats. We demonstrate a nongenomic glucocorticoid induction of long-lasting suppression of synaptic inhibition that is mediated by retrograde endocannabinoid release at GABA synapses. The rapid glucocorticoid-induced endocannabinoid suppression of synaptic inhibition is initiated by a membrane-associated glucocorticoid receptor in BLA principal neurons. We show that acute stress increases anxiety-like behavior via an endocannabinoid-dependent mechanism centered in the BLA. The stress-induced endocannabinoid modulation of synaptic transmission in the BLA contributes, therefore, to the stress regulation of anxiety, and may play a role in anxiety disorders of the amygdala.

Involvement of medial prefrontal cortex alpha-2 adrenoceptors on memory acquisition deficit induced by arachidonylcyclopropylamide, a cannabinoid CB1 receptor agonist, in rats; possible involvement of Ca2+ channels

Functional interactions between cannabinoid and alpha-2 adrenergic systems in cognitive control in the medial prefrontal cortex (mPFC) seem possible. The present study evaluated the possible role of alpha-2 adrenoceptors of the prefrontal cortex on effect of arachidonylcyclopropylamide (ACPA), a cannabinoid CB1 receptor (CB1R) agonist, in adult male Wistar rats. The animals were bilaterally implanted with chronic cannulae in the mPFC, trained in a step-through task, and tested 24 h after training to measure step-through latency. Results indicate that pre-training microinjection of ACPA (0.05 and 0.5 μg/rat) and clonidine (alpha-2 adrenoceptor agonist; 1 and 2 μg/rat) reduce memory acquisition. Pre-training subthreshold dose of clonidine (0.5 µg/rat) restored memory-impairing effect of ACPA (0.05 and 0.5 µg/rat). On the other hand, pre-training administration of the alpha-2 adrenoceptor antagonist yohimbine in all doses used (0.5, 1, and 2 μg/rat) did not affect memory acquisition by itself, while a subthreshold dose of yohimbine (2 µg/rat) potentiated memory impairment induced by ACPA (0.005 µg/rat). Finally, a subthreshold dose of SKF96365 (a Ca(2+) channel blocker) blocked clonidine and yohimbine effect of memory responses induced by ACPA. In conclusion, these data indicate that mPFC alpha-2 adrenoceptors play an important role in ACPA-induced amnesia and Ca(2+) channels have a critical role this phenomenon.

A2 noradrenergic neurons regulate forced swim test immobility

The Wistar-Kyoto (WKY) rat is a widely used animal model of depression, which is characterized by dysregulation of noradrenergic signaling. We previously demonstrated that WKY rats show a unique behavioral profile on the forced swim test (FST), characterized by high levels of immobility upon initial exposure and a greater learning-like response by further increasing immobility upon re-exposure than the genetically related Wistar rats. In the current study we aimed to determine whether altered activation of brainstem noradrenergic cell groups contributes to this behavioral profile. We exposed WKY and Wistar rats, to either 5min of forced swim or to the standard two-day FST (i.e. 15min forced swim on Day 1, followed by 5min on Day 2). We then stained their brains for FOS/tyrosine hydroxylase double-immunocytochemistry to determine potential differences in the activation of the brainstem noradrenergic cell groups. We detected a relative hyperactivation in the locus coeruleus of WKY rats when compared to Wistars in response to both one- and two-day forced swim. In contrast, within the A2 noradrenergic cell group, WKY rats exhibited diminished levels of FOS across both days of the FST, suggesting their lesser activation. We followed up these observations by selectively lesioning the A2 neurons, using anti-dopamine-β-hydroxylase-conjugated saporin, in Wistar rats, which resulted in increased FST immobility on both days of the test. Together these data indicate that the A2 noradrenergic cell group regulates FST behavior, and that its hypoactivation may contribute to the unique behavioral phenotype of WKY rats.

Inhibition of vasopressin V1a receptors in the medioventral bed nucleus of the stria terminalis has sex- and context-specific anxiogenic effects

Vasopressin V1a receptors (V1aR) are thought to contribute to the pathophysiology of psychiatric disorders such as anxiety and depression, sparking interest in V1aR as a therapeutic target. Although the global effects of V1aR have been documented, less is known about the specific neural circuits mediating these effects. Moreover, few studies have examined context-specific V1aR function in both males and females. By using the California mouse, we first studied the effects of sex and social defeat stress on V1aR binding in the forebrain. In females but not males, V1aR binding in the bed nucleus of the stria terminalis (BNST) was negatively correlated to social interaction behavior. In females stress also increased V1aR binding in the nucleus accumbens (NAc). Infusions of V1aR antagonist in to the medioventral BNST (BNSTmv) had anxiogenic effects only in animals naïve to defeat. For males, inhibition of V1aR in BNSTmv had anxiogenic effects in social and nonsocial contexts, but for females, anxiogenic effects were limited to social contexts. In stressed females, inhibition of V1aR in the NAc shell had no effect on social interaction behavior, but had an anxiogenic effect in an open field test. These data suggest that V1aR in BNSTmv have anxiolytic and prosocial effects in males, and that in females, prosocial and anxiolytic effects of V1aR appear to be mediated independently by receptors in the BNSTmv and NAc shell, respectively. These findings suggest that males have more overlap in neural circuits modulating anxiety in social and nonsocial contexts than females.

How Administration of the Beta-Blocker Propranolol Before Extinction can Prevent the Return of Fear

Combining beta-blockers with exposure therapy has been advocated to reduce fear, yet experimental studies combining beta-blockers with memory reactivation have had contradictory results. We explored how beta-blockade might affect the course of safety learning and the subsequent return of fear in a double-blind placebo-controlled functional magnetic resonance imaging study in humans (N=46). A single dose of propranolol before extinction learning caused a loss of conditioned fear responses, and prevented the subsequent return of fear and decreased explicit memory for the fearful events in the absence of drug. Fear-related neural responses were persistently attenuated in the dorsal medial prefrontal cortex (dmPFC), increased in the hippocampus 24 h later, and correlated with individual behavioral indices of fear. Prediction error-related responses in the ventral striatum persisted during beta-blockade. We suggest that this pattern of results is most consistent with a model where beta-blockade can prevent the return of fear by (i) reducing retrieval of fear memory, via the dmPFC and (ii) increasing contextual safety learning, via the hippocampus. Our findings suggest that retrieval of fear memory and contextual safety learning form potential mnemonic target mechanisms to optimize exposure-based therapy with beta-blockers.

CRF antagonism within the ventral tegmental area but not the extended amygdala attenuates the anxiogenic effects of cocaine in rats

In addition to its initial rewarding effects, cocaine has been shown to produce profound negative/anxiogenic actions. Recent work on the anxiogenic effects of cocaine has examined the role of corticotropin releasing factor (CRF), with particular attention paid to the CRF cell bodies resident to the extended amygdala (i.e., the central nucleus of the amygdala [CeA] and the bed nucleus of the stria terminalis [BNST]) and the interconnections within and projections outside the region (e.g., to the ventral tegmental area [VTA]). In the current study, localized CRF receptor antagonism was produced by intra-BNST, intra-CeA or intra-VTA application of the CRF antagonists, D-Phe CRF(12-41) or astressin-B. The effect of these treatments were examined in a runway model of i.v. cocaine self-administration that has been shown to be sensitive to both the initial rewarding and delayed anxiogenic effects of the drug in the same animal on the same trial. These dual actions of cocaine are reflected in the development of an approach-avoidance conflict ("retreat behaviors") about goal box entry that stems from the mixed associations that subjects form about the goal. CRF antagonism within the VTA, but not the CeA or BNST, significantly reduced the frequency of approach-avoidance retreat behaviors while leaving start latencies (an index of the positive incentive properties of cocaine) unaffected. These results suggest that the critical CRF receptors contributing to the anxiogenic state associated with acute cocaine administration may lie outside the extended amygdala, and likely involve CRF projections to the VTA.

Statins Promote Long-Term Recovery after Ischemic Stroke by Reconnecting Noradrenergic Neuronal Circuitry

Inhibitors of HMG-CoA reductase (statins), widely used to lower cholesterol in coronary heart and vascular disease, are effective drugs in reducing the risk of stroke and improving its outcome in the long term. After ischemic stroke, cardiac autonomic dysfunction and psychological problems are common complications related to deficits in the noradrenergic (NA) system. This study investigated the effects of statins on the recovery of NA neuron circuitry and its function after transient focal cerebral ischemia (tFCI). Using the wheat germ agglutinin (WGA) transgene technique combined with the recombinant adenoviral vector system, NA-specific neuronal pathways were labeled, and were identified in the locus coeruleus (LC), where NA neurons originate. NA circuitry in the atorvastatin-treated group recovered faster than in the vehicle-treated group. The damaged NA circuitry was partly reorganized with the gradual recovery of autonomic dysfunction and neurobehavioral deficit. Newly proliferated cells might contribute to reorganizing NA neurons and lead anatomic and functional recovery of NA neurons. Statins may be implicated to play facilitating roles in the recovery of the NA neuron and its function.

Evidence for involvement of a limbic paraventricular hypothalamic inhibitory network in hypothalamic-pituitary-adrenal axis adaptations to repeated stress

Emotional stressors activate a stereotyped set of limbic forebrain cell groups implicated in constraining stress-induced hypothalamic-pituitary-adrenal (HPA) axis activation by inhibiting hypophysiotropic neurons in the paraventricular hypothalamic nucleus (PVH). We previously identified a circumscribed, anterior part of the bed nuclei of the stria terminalis (aBST) that houses stress-sensitive, PVH-projecting, γ-aminobutyric acid (GABA)-ergic neurons as representing a site of convergence of stress-inhibitory influences originating from medial prefrontal and hippocampal cortices. Here we investigate whether exaggerated HPA axis responses associated with chronic variable stress (CVS; daily exposure to different stressors at unpredictable times over 14 days, followed by restraint stress on day 15) and diminished HPA output seen following repeated (14 days) restraint-stress exposure are associated with differential engagement of the limbic modulatory network. Relative to acutely restrained rats, animals subjected to CVS showed the expected increase (sensitization) in HPA responses and diminished levels of activation (Fos) of GABAergic neurons and glutamic acid decarboxylase (GAD) mRNA expression in the aBST. By contrast, repeated restraint stress produced habituation in HPA responses, maintained levels of activation of GABAergic neurons, and increased GAD expression in the aBST. aBST-projecting neurons in limbic sites implicated in HPA axis inhibition tended to show diminished activational responses in both repeated-stress paradigms, with the exception of the paraventricular thalamic nucleus, in which responsiveness was maintained in repeatedly restrained animals. The results are consistent with the view that differential engagement of HPA inhibitory mechanisms in the aBST may contribute to alterations in HPA axis responses to emotional stress in sensitization and habituation paradigms.

Guanfacine enhances inhibitory control and attentional shifting in early abstinent cocaine-dependent individuals

OBJECTIVES

Attenuation of adrenergic drive and cognitive enhancement, via stimulation of alpha2 pre- and post-synaptic receptors, may selectively enhance executive performance in early abstinent cocaine-dependent individuals. As these cognitive processes underpin important treatment-related behaviors, the alpha2 agonist, guanfacine HCl, may represent an effective pharmaco-therapeutic intervention.

METHODS

Twenty-five early abstinent cocaine-dependent individuals were administered a battery of neurocognitive tasks on entry into treatment (baseline) and again following 3 weeks of either placebo or guanfacine treatment (up to 3 mg). Tasks included: Stop Signal, Stroop, 3-Dimentional Intra-dimensional/Extra-dimensional (IDED) task, Spatial Working Memory (SWM), Paired Associates Learning (PAL), Verbal Fluency and the Rey Auditory Verbal Learning Test (RAVLT).

RESULTS

Compared with placebo, the guanfacine group demonstrated attenuated anxiety and negative affect as well as improved performance on selective executive tests. This included fewer directional errors on the stop signal task, fewer errors on the extra-dimensional shift component of the IDED task and better attentional switching during verbal fluency. Guanfacine did not improve strategic working memory or peripheral memory.

CONCLUSION

Guanfacine improves selective cognitive processes which may underlie salient treatment-related regulatory behaviors. Alpha2 agonists may therefore represent important agents for cocaine dependence.

Effects of fetal microwave radiation exposure on offspring behavior in mice

The recent rapid development of electronic communication techniques is resulting in a marked increase in exposure of humans to electromagnetic fields (EMFs). This has raised public concerns about the health hazards of long-term environmental EMF exposure for fetuses and children. Some studies have suggested EMF exposure in children could induce nervous system disorders. However, gender-dependent effects of microwave radiation exposure on cognitive dysfunction have not previously been reported. Here we investigated whether in utero exposure to 9.417-GHz microwave throughout gestation (Days 3.5-18) affected behavior, using the open field test (OFT), elevated-plus maze (EPM), tail suspension test (TST), forced swimming test (FST) and Morris water maze (MWM). We found that mice showed less movement in the center of an open field (using the OFT) and in an open arm (using the EPM) after in utero exposure to 9.417-GHz radiation, which suggested that the mice had increased anxiety-related behavior. Mice demonstrated reduced immobility in TST and FST after in utero exposure to 9.417-GHz radiation, which suggested that the mice had decreased depression-related behavior. From the MWM test, we observed that male offspring demonstrated decreased learning and memory, while females were not affected in learning and memory, which suggested that microwaves had gender-dependent effects. In summary, we have provided the first experimental evidence of microwaves inducing gender-dependent effects.

Prior extended daily access to cocaine elevates the reward threshold in a conditioned place preference test

We have previously shown that extended-access subjects exhibit heightened motivation for cocaine in the runway model, as reflected by reduced number of retreats. This heightened motivation could reflect either an increase in cocaine-induced reward or a decrease in cocaine-induced aversion. The current experiment was therefore devised to assess the cocaine-induced reward and aversion in extended-access rats using a place conditioning test. Rats trained to lever press for intravenous (IV) cocaine (0.25 mg/infusion) were provided 6-hour daily access to the drug over 10 days. Lever pressing in control subjects produced IV infusions of saline. Following drug self-administration, subjects underwent place conditioning for the immediate or delayed effects of cocaine (1.0 or 2.5 mg/kg, IV). In control subjects, the immediate effects of the low dose of cocaine produced conditioned places preferences (CPPs), while the delayed effects produced conditioned place aversions (CPAs). In contrast, the animals receiving low cocaine dose for 6 hours, exhibited place aversions but not preferences; an effect that was reversed when the dose of cocaine was increased. Additionally, in the 6-hour group, delayed conditioning was associated with a reduction in zif268 immunoreactivity in the medial prefrontal cortex and nucleus accumbens shell while immediate conditioning was associated with an increase in zif268-positive cells in the central nucleus of the amygdala. Collectively, these data suggest that extended daily access to cocaine produces a shift in the subject's perceived reward threshold that is paralleled by alterations in the activity of both the reward and stress pathways.

Excitatory drive onto dopaminergic neurons in the rostral linear nucleus is enhanced by norepinephrine in an α1 adrenergic receptor-dependent manner

Dopaminergic innervation of the extended amygdala regulates anxiety-like behavior and stress responsivity. A portion of this dopamine input arises from dopamine neurons located in the ventral lateral periaqueductal gray (vlPAG) and rostral (RLi) and caudal linear nuclei of the raphe (CLi). These neurons receive substantial norepinephrine input, which may prime them for involvement in stress responses. Using a mouse line that expresses eGFP under control of the tyrosine hydroxylase promoter, we explored the physiology and responsiveness to norepinephrine of these neurons. We find that RLi dopamine neurons differ from VTA dopamine neurons with respect to membrane resistance, capacitance and the hyperpolarization-activated current, Ih. Further, we found that norepinephrine increased the frequency of spontaneous excitatory postsynaptic currents (sEPSCs) on RLi dopamine neurons. This effect was mediated through the α1 adrenergic receptor (AR), as the actions of norepinephrine were mimicked by the α1-AR agonist methoxamine and blocked by the α1-AR antagonist prazosin. This action of norepinephrine on sEPSCs was transient, as it did not persist in the presence of prazosin. Methoxamine also increased the frequency of miniature EPSCs, indicating that the α1-AR action on glutamatergic transmission likely has a presynaptic mechanism. There was also a modest decrease in sEPSC frequency with the application of the α2-AR agonist UK-14,304. These studies illustrate a potential mechanism through which norepinephrine could recruit the activity of this population of dopaminergic neurons.

Noradrenergic β-receptor antagonism within the central nucleus of the amygdala or bed nucleus of the stria terminalis attenuates the negative/anxiogenic effects of cocaine

Cocaine has been shown to produce both initial rewarding and delayed anxiogenic effects. Although the neurobiology of cocaine's rewarding effects has been well studied, the mechanisms underlying its anxiogenic effects remain unclear. We used two behavioral assays to study these opposing actions of cocaine: a runway self-administration test and a modified place conditioning test. In the runway, the positive and negative effects of cocaine are reflected in the frequency of approach-avoidance conflict that animals develop about entering a goal box associated with cocaine delivery. In the place conditioning test, animals develop preferences for environments paired with the immediate/rewarding effects of cocaine, but avoid environments paired with the drug's delayed/anxiogenic actions. In the present study, these two behavioral assays were used to examine the role of norepinephrine (NE) transmission within the central nucleus of the amygdala (CeA) and the bed nucleus of the stria terminalis (BNST), each of which has been implicated in drug-withdrawal-induced anxiety and stress-induced response reinstatement. Rats experienced 15 single daily cocaine-reinforced (1.0 mg/kg, i.v.) runway trials 10 min after intracranial injection of the β1 and β2 NE receptor antagonists betaxolol and ICI 118551 or vehicle into the CeA or BNST. NE antagonism of either region dose dependently reduced approach-avoidance conflict behavior compared with that observed in vehicle-treated controls. In addition, NE antagonism selectively interfered with the expression of conditioned place aversions while leaving intact cocaine-induced place preferences. These data suggest a role for NE signaling within the BNST and the CeA in the anxiogenic actions of cocaine.

Both α1- and α2-adrenoceptors in the insular cortex are involved in the cardiovascular responses to acute restraint stress in rats

The insular cortex (IC) is a limbic structure involved in cardiovascular responses observed during aversive threats. However, the specific neurotransmitter mediating IC control of cardiovascular adjustments to stress is yet unknown. Therefore, in the present study we investigated the role of local IC adrenoceptors in the cardiovascular responses elicited by acute restraint stress in rats. Bilateral microinjection of different doses (0.3, 5, 10 and 15 nmol/100 nl) of the selective α1-adrenoceptor antagonist WB4101 into the IC reduced both the arterial pressure and heart rate increases elicited by restraint stress. However, local IC treatment with different doses (0.3, 5, 10 and 15 nmol/100 nl) of the selective α2-adrenoceptor antagonist RX821002 reduced restraint-evoked tachycardia without affecting the pressor response. The present findings are the first direct evidence showing the involvement of IC adrenoceptors in cardiovascular adjustments observed during aversive threats. Our findings indicate that IC noradrenergic neurotransmission acting through activation of both α1- and α2-adrenoceptors has a facilitatory influence on pressor response to acute restraint stress. Moreover, IC α1-adrenoceptors also play a facilitatory role on restraint-evoked tachycardiac response.

Differential postpartum sensitivity to the anxiety-modulating effects of offspring contact is associated with innate anxiety and brainstem levels of dopamine beta-hydroxylase in female laboratory rats

In female mammals, the postpartum period involves dramatic shifts in many socioemotional behaviors. This includes a suppression of anxiety-related behaviors that requires recent physical contact with offspring. Factors contributing to differences among females in their susceptibility to the anxiety-modulating effect of offspring contact are unknown, but could include their innate anxiety and brain monoaminergic activity. Anxiety behavior was assessed in a large group of nulliparous female rats and the least-anxious and most-anxious tertiles were mated. Anxiety was assessed again postpartum after females were permitted or prevented from contacting their offspring 4 h before testing. Levels of dopamine β-hydroxylase (DBH, norepinephrine synthesizing enzyme) and tryptophan hydroxylase-2 (TPH2, serotonin synthesizing enzyme) were measured in the brainstem and dorsal raphe, respectively. It was found that anxiety-related behavior in the two groups did not differ when dams were permitted contact with offspring before testing. Removal of the offspring before testing, however, differentially affected anxiety based on dams' innate anxiety. Specifically, dams reverted back to their pre-mating levels of anxiety such that offspring removal slightly increased anxiety in the most-anxious females but greatly lowered anxiety in the least-anxious females. This reduction in anxiety in the least-anxious females after litter removal was associated with lower brainstem DBH. There was no relationship between females' anxiety and dorsal raphe TPH2. Thus, a primary effect of recent contact with offspring on anxiety-related behavior in postpartum rats is to shift females away from their innate anxiety to a more moderate level of responding. This effect is particularly true for females with the lowest anxiety, may be mediated by central noradrenergic systems, and has implications for their ability to attend to their offspring.

Direct targeting of peptidergic amygdalar neurons by noradrenergic afferents: linking stress-integrative circuitry

Amygdalar norepinephrine (NE) plays a key role in regulating neural responses to emotionally arousing stimuli and is involved in memory consolidation of emotionally charged events. Corticotropin-releasing factor (CRF) and dynorphin (DYN), two neuropeptides that mediate the physiological and behavioral responses to stress, are abundant in the central nucleus of the amygdala (CeA), and directly innervate brainstem noradrenergic locus coeruleus (LC) neurons. Whether the CRF- and DYN-containing amygdalar neurons receive direct noradrenergic innervation has not yet been elucidated. The present study sought to define cellular substrates underlying noradrenergic modulation of CRF- and DYN-containing neurons in the CeA using immunohistochemistry and electron microscopy. Ultrastructural analysis revealed that NE-labeled axon terminals form synapses with CRF- and DYN-containing neurons in the CeA. Semi-quantitative analysis showed that approximately 31 % of NET-labeled axon terminals targeted CeA neurons that co-expressed DYN and CRF. As a major source of CRF innervation to the LC, it is also not known whether CRF-containing CeA neurons are directly targeted by noradrenergic afferents. To test this, retrograde tract tracing using FluoroGold from the LC was combined with immunocytochemical detection of CRF and NET in the CeA. Our results revealed a population of LC-projecting CRF-containing CeA neurons that are directly innervated by NE afferents. Analysis showed that approximately 34 % of NET-labeled axon terminals targeted LC-projecting CeA neurons that contain CRF. Taken together, these results indicate significant interactions between NE, CRF and DYN in this critical limbic region and reveal direct synaptic interactions of NE with amygdalar CRF that influence the LC-NE arousal system.

Being a grump only makes things worse: a transactional account of acute stress on mind wandering

The current work investigates the influence of acute stress on mind wandering. Participants completed the Positive and Negative Affect Schedule as a measure of baseline negative mood, and were randomly assigned to either the high-stress or low-stress version of the Trier Social Stress Test. Participants then completed the Sustained Attention to Response Task as a measure of mind-wandering behavior. In Experiment 1, participants reporting a high degree of negative mood that were exposed to the high-stress condition were more likely to engage in a variable response time, make more errors, and were more likely to report thinking about the stressor relative to participants that report a low level of negative mood. These effects diminished throughout task performance, suggesting that acute stress induces a temporary mind-wandering state in participants with a negative mood. The temporary affect-dependent deficits observed in Experiment 1 were replicated in Experiment 2, with the high negative mood participants demonstrating limited resource availability (indicated by pupil diameter) immediately following stress induction. These experiments provide novel evidence to suggest that acute psychosocial stress briefly suppresses the availability of cognitive resources and promotes an internally oriented focus of attention in participants with a negative mood.

The effects of varied extinction procedures on contingent cue-induced reinstatement in Sprague-Dawley rats

RATIONALE

Cue exposure therapy, which attempts to limit relapse by reducing reactivity to cocaine-paired cues through repeated exposures, has had limited success.

OBJECTIVES

The current experiments examined cocaine cue-induced anxiogenesis and investigated whether a model of cue exposure therapy would reduce reinstatement of cocaine seeking in rats with a history of cocaine self-administration.

METHODS

Male rats experienced daily intravenous cocaine self-administration. Rats then experienced exposure to either the self-administration context or the context plus noncontingent presentations of cocaine-paired cues. Immediately following exposure, anxiety-like behavior was measured using elevated plus maze and defensive burying tests. In a second group of rats, self-administration was followed by 7 days of exposure to the context, context + noncontingent cue exposure, lever extinction, or cue + lever extinction. All animals then underwent two contingent cue-induced reinstatement tests separated by 7 days of lever extinction.

RESULTS

Exposure to noncontingent cocaine-paired cues in the self-administration context increased anxiety-like behavior on the defensive burying test. Animals that experienced lever + cue extinction displayed the least cocaine seeking on the first reinstatement test, and lever extinction reduced cocaine seeking below context exposure or context + noncontingent cue exposure. All animals had similar levels of cocaine seeking on the second reinstatement test.

CONCLUSION

Noncontingent cue exposure causes anxiety, and noncontingent cue and context exposure are less effective at reducing contingent cue-induced reinstatement than lever or lever + cue extinction. These data indicate that active extinction of the drug-taking response may be critical for reduction of relapse proclivity in former cocaine users.

Noradrenergic neurotransmission within the bed nucleus of the stria terminalis modulates the retention of immobility in the rat forced swimming test

The bed nucleus of the stria terminalis (BNST) is a limbic structure that has a direct influence on the autonomic, neuroendocrine, and behavioral responses to stress. It was recently reported that reversible inactivation of synaptic transmission within this structure causes antidepressant-like effects, indicating that activation of the BNST during stressful situations would facilitate the development of behavioral changes related to the neurobiology of depression. Moreover, noradrenergic neurotransmission is abundant in the BNST and has an important role in the regulation of emotional processes related to the stress response. Thus, this study aimed to test the hypothesis that activation of adrenoceptors within the BNST facilitates the development of behavioral consequences of stress. To investigate this hypothesis, male Wistar rats were stressed (forced swimming, 15 min) and 24 h later received intra-BNST injections of vehicle, WB4101, RX821002, CGP20712, or ICI118,551, which are selective α(1), α(2), β(1), and β(2) adrenoceptor antagonists, respectively, 10 min before a 5-min forced swimming test. It was observed that administration of WB4101 (10 and 15 nmol), CGP20712 (5 and 10 nmol), or ICI118,551 (5 nmol) into the BNST reduced the immobility time of rats subjected to forced swimming test, indicating an antidepressant-like effect. These findings suggest that activation of α(1), β(1), and β(2) adrenoceptors in the BNST could be involved in the development of the behavioral consequences of stress.

Inactivation of glucocorticoid receptor in noradrenergic system influences anxiety- and depressive-like behavior in mice

The aim of this study was to investigate whether conditional inactivation of the glucocorticoid receptors (GRs) in noradrenergic neurons affects animal behavior in mice. Selective ablation of GRs in the noradrenergic system was achieved using the Cre/loxP approach. We crossed transgenic mice expressing the Cre recombinase under the dopamine beta-hydroxylase (DBH) promoter with animals harboring the floxed GR gene. The resulting GR(DBHCre) mutant mice exhibited no alterations in terms of normal cage behavior, weight gain, spatial memory or spontaneous locomotor activity, regardless of gender. To assess depressive- and anxiety-like behaviors we performed the Tail Suspension Test and the Light-Dark Box Test. While male mutant animals did not show any alternations in both tests, female GR(DBHCre) mutants displayed depressive- and anxiety-like behavior. Additionally, male GR(DBHCre) mice were exposed to chronic restraint stress but still exhibited immobility times and anxiety statuses similar to those of non-stressed animals while stressed control mice clearly revealed depressive- and anxiety-like phenotype. Thus, in males the effects of the mutation were precipitated only after chronic restraint stress procedure. Our data reveal a possible gender-dependent role of GRs in the noradrenergic system in anxiety- and depressive-like behavior in mice.

Noradrenergic alpha-2 receptor modulators in the ventral bed nucleus of the stria terminalis: effects on anxiety behavior in postpartum and virgin female rats

Emotional hyperreactivity can inhibit maternal responsiveness in female rats and other animals. Maternal behavior in postpartum rats is disrupted by increasing norepinephrine release in the ventral bed nucleus of the stria terminalis (BSTv) with the α2-autoreceptor antagonist, yohimbine, or the more selective α2-autoreceptor antagonist, idazoxan (Smith et al., 2012). Because high noradrenergic activity in the BSTv can also increase anxiety-related behaviors, increased anxiety may underlie the disrupted mothering of dams given yohimbine or idazoxan. To assess this possibility, anxiety-related behaviors in an elevated plus maze were assessed in postpartum rats after administration of yohimbine or idazoxan. It was further assessed if the α2-autoreceptor agonist clonidine (which decreases norepinephrine release) would, conversely, reduce dams' anxiety. Groups of diestrous virgins were also examined. It was found that peripheral or intra-BSTv yohimbine did increase anxiety-related behavior in postpartum females. However, BSTv infusion of idazoxan did not reproduce yohimbine's anxiogenic effects and anxiety was not reduced by peripheral or intra-BSTv clonidine. Because yohimbine is a weak 5HT1A receptor agonist, other groups of females received BSTv infusion of the 5HT1A receptor agonist 8OH-DPAT, but it did not alter their anxiety-related behavior. Lastly, levels of norepinephrine and serotonin in tissue punches from the BSTv did not differ between postpartum and diestrous rats, but serotonin turnover was lower in mothers. These results suggest that the impaired maternal behavior after BSTv infusion of yohimbine or idazoxan cannot both be readily explained by an increase in dams' anxiety, and that BSTv α2-autoreceptor modulation alone has little influence on anxiety-related behaviors in postpartum or diestrous rats.

Does exposure to chronic stress influence blood pressure in rats?

The principal aim of this study was to determine whether prolonged chronic footshock stress can evoke sustained changes in blood pressure in rats and to elucidate possible underlying neurochemical mechanisms as mediated by the sympathoadrenal system. Adult male Wistar rats instrumented for telemetric recording of arterial pressure, heart rate and locomotor activity were subjected to six weeks of inescapable unpredictable electrical footshocks (FS+) or were exposed to shock chambers but were not shocked (FS-). Compared to FS- animals, FS+ animals had significantly reduced body weight gain (by 30%), locomotor activity (by 25%) and social interaction time (by 30%)--symptoms commonly induced by chronic stress and depression in humans. These changes were associated with small, but significant increases in systolic blood pressure (by 7%) and pulse pressure (by 11%) in FS+ rats relative to FS- rats. We have also found neurochemical alterations in sympathoadrenal pathways (that lasted for at least one week post-stress) including about 2-3 fold increases in the levels of tyrosine hydroxylase phosphorylation in the sympathetic ganglia and adrenal gland and a 1.8-fold increase in the expression of the Angiotensin II receptor type 1 protein in the adrenal gland of FS+ rats relative to FS- rats. We conclude that uncontrollable and unpredictable footshock stress can lead to elevation in systolic blood pressure when applied for an extended period of time (six weeks) in Wistar rats, and that these changes could be mediated by stress-induced modifications in sympathoadrenal pathways.

Noradrenergic control of the bed nucleus of the stria terminalis in stress and reward

The bed nucleus of the stria terminalis (BNST) is a group of inter-connected subnuclei that play critical roles in stress-reward interactions. An interesting feature of this brain region is the massive noradrenergic input that it receives. Important roles for norepinephrine in this region have been documented in a number of stress and reward related behaviors. This work has been paralleled over the last several years by efforts to understand the actions of norepinephrine on neuronal function in the region. In this review, we will summarize the current state of these research areas.

Too much of a good thing: blocking noradrenergic facilitation in medial prefrontal cortex prevents the detrimental effects of chronic stress on cognition

Cognitive impairments associated with dysfunction of the medial prefrontal cortex (mPFC) are prominent in stress-related psychiatric disorders. We have shown that enhancing noradrenergic tone acutely in the rat mPFC facilitated extra-dimensional (ED) set-shifting on the attentional set-shifting test (AST), whereas chronic unpredictable stress (CUS) impaired ED. In this study, we tested the hypothesis that the acute facilitatory effect of norepinephrine (NE) in mPFC becomes detrimental when activated repeatedly during CUS. Using microdialysis, we showed that the release of NE evoked in mPFC by acute stress was unchanged at the end of CUS treatment. Thus, to then determine if repeated elicitation of this NE activity in mPFC during CUS may have contributed to the ED deficit, we infused a cocktail of α(1)-, β(1)-, and β(2)-adrenergic receptor antagonists into the mPFC prior to each CUS session, then tested animals drug free on the AST. Antagonist treatment prevented the CUS-induced ED deficit, suggesting that NE signaling during CUS compromised mPFC function. We confirmed that this was not attributable to sensitization of adrenergic receptor function following chronic antagonist treatment, by administering an additional microinjection into the mPFC immediately prior to ED testing. Acute antagonist treatment did not reverse the beneficial effects of chronic drug treatment during CUS, nor have any effect on baseline ED performance in chronic vehicle controls. Thus, we conclude that blockade of noradrenergic receptors in mPFC protected against the detrimental cognitive effects of CUS, and that repeated elicitation of noradrenergic facilitatory activity is one mechanism by which chronic stress may promote mPFC cognitive dysfunction.

Yohimbine anxiogenesis in the elevated plus maze requires hindbrain noradrenergic neurons that target the anterior ventrolateral bed nucleus of the stria terminalis

The α2 adrenergic receptor antagonist yohimbine (YO) increases transmitter release from noradrenergic (NA) terminals in cortical and subcortical brain regions, including the bed nucleus of the stria terminalis (BST). YO activates the hypothalamic-pituitary-adrenal (HPA) stress axis and is potently anxiogenic in rats and humans. We previously reported that hindbrain NA neurons within the caudal nucleus of the solitary tract (NST-A2/C2) and ventrolateral medulla (VLM-A1/C1) that innervate the anterior ventrolateral (vl)BST contribute to the ability of YO to activate the HPA stress axis in rats. To determine whether the same NA pathway also contributes to YO-induced anxiogenesis in the elevated plus maze (EPMZ), a selective saporin ribotoxin conjugate (dopamine beta hydroxylase conjugated to saporin toxin, DSAP) was microinjected bilaterally into the anterior vlBST to destroy its NA inputs. Sham-lesioned controls were microinjected with vehicle. Two experiments were conducted to determine DSAP lesion effects on EPMZ behavior. DSAP lesions did not alter maze behavior in rats after intraperitoneal saline, and did not alter the significant effect of prior maze experience to reduce exploratory and open arm maze activities. However, in maze-naïve rats, DSAP lesions abolished YO anxiogenesis in the EPMZ. Post-mortem immunocytochemical analyses confirmed that DSAP consistently ablated caudal NST-A2/C2 and VLM-A1/C1 neurons that innervate the anterior vlBST. DSAP lesions did not destroy non-NA inputs to the anterior vlBST, and produced inconsistent cell loss within the pontine locus coeruleus (A6 cell group) that was unrelated to YO anxiogenesis. Thus, the ability of YO to increase anxiety-like behavior in the EPMZ depends on hindbrain NA neurons that target the anterior vlBST.