Differential effects of the stress peptides PACAP and CRF on sleep architecture in mice.

Stress produces profound effects on behavior, including persistent alterations in sleep patterns. Here we examined the effects of two prototypical stress peptides, pituitary adenylate cyclase-activating polypeptide (PACAP) and corticotropin-releasing factor (CRF), on sleep architecture and other translationally-relevant endpoints. Male and female mice were implanted with subcutaneous transmitters enabling continuous measurement of electroencephalography (EEG) and electromyography (EMG), as well as body temperature and locomotor activity, without tethering that restricts free movement, body posture, or head orientation during sleep. At baseline, females spent more time awake (AW) and less time in slow wave sleep (SWS) than males. Mice then received intracerebral infusions of PACAP or CRF at doses producing equivalent increases in anxiety-like behavior. The effects of PACAP on sleep architecture were similar in both sexes and resembled those reported in male mice after chronic stress exposure. Compared to vehicle infusions, PACAP infusions decreased time in AW, increased time in SWS, and increased rapid eye movement sleep (REM) time and bouts on the day following treatment. In addition, PACAP effects on REM time remained detectable a week after treatment. PACAP infusions also reduced body temperature and locomotor activity. Under the same experimental conditions, CRF infusions had minimal effects on sleep architecture in either sex, causing only transient increases in SWS during the dark phase, with no effects on temperature or activity. These findings suggest that PACAP and CRF have fundamentally different effects on sleep-related metrics, and provide new insights into the mechanisms by which stress disrupts sleep.

Behavioral methods to study anxiety in rodents.

Stress is a precipitating factor for anxiety-related disorders, which are among the leading forms of psychiatric illness and impairment in the modern world. Rodent-based behavioral tests and models are widely used to understand the mechanisms by which stress triggers anxiety-related behaviors and to identify new treatments for anxiety-related disorders. Although substantial progress has been made and many of the key neural circuits and molecular pathways mediating stress responsiveness have been characterized, these advances have thus far failed to translate into fundamentally new treatments that are safer and more efficacious in humans. The purpose of this article is to describe methods that have been historically used for this type of research and to highlight new approaches that align with recent conceptualizations of disease symptomatology and that may ultimately prove to be more fruitful in facilitating the development of improved therapeutics.

El estrés es un factor precipitante para los trastornos relacionados con la ansiedad, los cuales están entre las principales formas de enfermedad psiquiátrica y discapacidad en el mundo moderno. Los modelos y las pruebas conductuales basadas en roedores son ampliamente empleadas para la comprensión de los mecanismos mediante los cuales el estrés gatilla conductas relacionadas con la ansiedad y para identificar nuevos tratamientos para los trastornos relacionados con la ansiedad. Aunque ha habido un significativo progreso y se han caracterizado muchos de los circuitos neurales y vías moleculares clave que median la respuesta de estrés, estos avances han sido insuficientes para traducirse en tratamientos fundamentalmente nuevos que sean más seguros y más eficaces en humanos. El propósito de este artículo es describir los métodos que se han empleado históricamente en este tipo de investigación y destacar los nuevos enfoques que sean concordantes con las conceptualizaciones recientes de la sintomatología de la enfermedad, susceptibles de ser finalmente los más fructíferos para facilitar el desarrollo de los mejores tratamientos.

Le stress est un facteur précipitant des troubles liés à l'anxiété qui représentent la majorité des maladies et du handicap psychiatriques du monde moderne. Des modèles et des tests comportementaux sont largement utilisés chez les rongeurs pour comprendre les mécanismes par lesquels le stress déclenche des comportements anxieux et pour identifier de nouveaux traitements des troubles liés à l'anxiété. Des progrès importants ont été réalisés et de nombreux circuits neuronaux et voies moléculaires clés véhiculant la réactivité au stress ont été caractérisés, mais ces avancées n'ont pas, jusqu'à présent, réussi à se traduire en nouveaux traitements réellement plus sûrs et plus efficaces chez l'homme. Cet article a pour but de décrire les méthodes historiques utilisées pour ce type de recherche et de souligner les nouvelles approches concordant avec les conceptions récentes de la symptomatologie de la maladie susceptibles d'être finalement plus fructueuses pour faciliter le développement de meilleurs traitements.

Regulation of bed nucleus of the stria terminalis PACAP expression by stress and corticosterone.

Single-nucleotide polymorphisms (SNPs) in the genes for pituitary adenylyl cyclase-activating peptide (PACAP) and the PAC1 receptor have been associated with stress-related psychiatric disorders. Although, from recent work, we have argued that stress-induced PACAP expression in the bed nucleus of the stria terminalis (BNST) may mediate stress-related psychopathology, it is unclear whether stress-induced increases in BNST PACAP expression require acute or repeated stressor exposure and whether increased BNST PACAP expression is related to stress-induced increases in circulating glucocorticoids. In the current work, we have used real-time quantitative polymerase chain reaction (qPCR) to assess transcript expression in brain punches from rats after stressor exposure paradigms or corticosterone injection. BNST PACAP and PAC1 receptor transcript expression was increased only after 7 days of repeated stressor exposure; no changes in transcript levels were observed 2 or 24 hours after a single-restraint session. Moreover, repeated corticosterone treatment for 7 days was not sufficient to reliably increase BNST PACAP transcript levels, suggesting that stress-induced elevations in corticosterone may not be the primary drivers of BNST PACAP expression. These results may help clarify the mechanisms and temporal processes that underlie BNST PACAP induction for intervention in stress-related anxiety disorders.

PACAP in the BNST produces anorexia and weight loss in male and female rats.

Recent gene association studies have implicated pituitary adenylate cyclase-activating peptide (PACAP) systems in several psychiatric disorders associated with stressor exposure, and we have argued that many of the behavioral consequences of repeated stressor exposure may depend on the expression of PACAP in the bed nucleus of the stria terminalis (BNST). One behavioral consequence of the activation of stress systems can be anorexia and subsequent weight loss, and both the activation of central PACAP systems as well as neuronal activity in the BNST have also been associated with anorexic states in rodents. Hence, we investigated the regulation of food and water intake and weight loss following BNST PACAP infusion. BNST PACAP38 dose-dependently decreased body weight, as well as food and water intake in the first 24 h following infusion. Because different BNST subregions differentially regulate stress responding, we further examined the effects of PACAP38 in either the anterior or posterior BNST. Anterior BNST PACAP38 infusion did not alter weight gain, whereas posterior PACAP38 infusion resulted in weight loss. PACAP38 infused into the lateral ventricles did not alter weight, suggesting that the effects of BNST-infused PACAP were not mediated by leakage into the ventricular system. These data suggest that PACAP receptor activation in posterior BNST subregions can produce anorexia and weight loss, and corroborate growing data implicating central PACAP activation in mediating the consequences of stressor exposure.

Excitotoxic lesions of the bed nucleus of the stria terminalis (BNST) attenuate the effects of repeated stress on weight gain: evidence for the recruitment of BNST activity by repeated, but not acute, stress.

Exposure to repeated stress can lead to diverse and widespread behavioral consequences, including reduction in food and water intake and subsequent diminution in weight gain. Many reports have suggested that repeated stress substantially alters the neurochemistry, morphology and physiology of neurons within the bed nucleus of the stria terminalis (BNST). Here we investigate the role of the BNST in mediating the reduced weight gain observed during repeated stress. Rats exposed to a one-week variate stress paradigm exhibited a reduction in weight gain over the course of the 7-day paradigm. Excitotoxic lesions to a subregion of the anterolateral BNST containing the oval nucleus had no effects early in the 7-day paradigm, but significantly attenuated the effects of repeated stress on weight gain by the last day of stress. These data suggest that at least two mechanisms mediate the effects of stress on body weight gain, and that when stressor exposure becomes repeated, the BNST is recruited, worsening the symptoms of stressor exposure.

Overlapping neurobiology of learned helplessness and conditioned defeat: implications for PTSD and mood disorders.

Exposure to traumatic events can increase the risk for major depressive disorder (MDD) as well as posttraumatic stress disorder (PTSD), and pharmacological treatments for these disorders often involve the modulation of serotonergic (5-HT) systems. Several behavioral paradigms in rodents produce changes in behavior that resemble symptoms of MDD and these behavioral changes are sensitive to antidepressant treatments. Here we review two animal models in which MDD-like behavioral changes are elicited by exposure to an acute traumatic event during adulthood, learned helplessness (LH) and conditioned defeat. In LH, exposure of rats to inescapable, but not escapable, tailshock produces a constellation of behavioral changes that include deficits in fight/flight responding and enhanced anxiety-like behavior. In conditioned defeat, exposure of Syrian hamsters to a social defeat by a more aggressive animal leads to a loss of territorial aggression and an increase in submissive and defensive behaviors in subsequent encounters with non-aggressive conspecifics. Investigations into the neural substrates that control LH and conditioned defeat revealed that increased 5-HT activity in the dorsal raphe nucleus (DRN) is critical for both models. Other key brain regions that regulate the acquisition and/or expression of behavior in these two paradigms include the basolateral amygdala (BLA), central nucleus of the amygdala (CeA) and bed nucleus of the stria terminalis (BNST). In this review, we compare and contrast the role of each of these neural structures in mediating LH and conditioned defeat, and discuss the relevance of these data in developing a better understanding of the mechanisms underlying trauma-related depression. This article is part of a Special Issue entitled 'Post-Traumatic Stress Disorder'.

Roles for pituitary adenylate cyclase-activating peptide (PACAP) expression and signaling in the bed nucleus of the stria terminalis (BNST) in mediating the behavioral consequences of chronic stress.

Anxiety disorders are frequently long-lasting and debilitating for more than 40 million American adults. Although stressor exposure plays an important role in the etiology of some anxiety disorders, the mechanisms by which exposure to stressful stimuli alters central circuits that mediate anxiety-like emotional behavior are still unknown. Substantial evidence has implicated regions of the central extended amygdala, including the bed nucleus of the stria terminalis (BNST) and the central nucleus of the amygdala as critical structures mediating fear- and anxiety-like behavior in both humans and animals. These areas organize coordinated fear- and anxiety-like behavioral responses as well as peripheral stress responding to threats via direct and indirect projections to the paraventricular nucleus of the hypothalamus and brainstem regions (Walker et al. Eur J Pharmacol 463:199-216, 2003, Prog Neuropsychopharmacol Biol Psychiatry 33(8):1291-1308, 2009; Ulrich-Lai and Herman Nat Rev Neurosci 10:397-409, 2009). In particular, the BNST has been argued to mediate these central and peripheral responses when the perceived threat is of long duration (Waddell et al. Behav Neurosci 120:324-336, 2006) and/or when the anxiety-like response is sustained (Walker and Davis Brain Struct Funct 213:29-42, 2008); hence, the BNST may mediate pathological anxiety-like states that result from exposure to chronic stress. Indeed, chronic stress paradigms result in enhanced BNST neuroplasticity that has been associated with pathological anxiety-like states (Vyas et al. Brain Res 965:290-294, 2003; Pego et al. Eur J Neurosci 27:1503-1516, 2008). Here we review evidence that suggests that pituitary adenylate cyclase-activating polypeptide (PACAP) and corticotropin-releasing hormone (CRH) work together to modulate BNST function and increase anxiety-like behavior. Moreover, we have shown that BNST PACAP as well as its cognate PAC1 receptor is substantially upregulated following chronic stress, particularly in the BNST oval nucleus where PACAP-containing neurons closely interact with CRH-containing neurons (Kozicz et al. Brain Res 767:109-119, 1997; Hammack et al. Psychoneuroendocrinology 34:833-843, 2009). We describe how interactions between PACAP and CRH in the BNST may mediate stress-associated behaviors, including anorexia and anxiety-like behavior. These studies have the potential to define specific mechanisms underlying anxiety disorders, and may provide important therapeutic strategies for stress and anxiety management.