The role of neuropeptide Y in the amygdala on corticotropin-releasing factor receptor-mediated behavioral stress responses in the rat

Neuropeptide Y (NPY) is one of the most abundant peptides in the brain and has been shown to be a critical regulator of emotionality, most notably for its effect in decreasing anxiety-like behaviors. The stress response in both humans and animals has been shown to involve a cascade of biological events initiated by corticotropin releasing factor (CRF), another centrally acting peptide. Interestingly, NPY and CRF are present in similar brain regions mediating stress responses and may act in an opposing fashion. The basolateral nucleus of the amygdala (BLA) is a distinct division of the amygdala and contains CRF receptors and the highest concentration of NPY neurons. The current study investigates the behavioral effects in rodents when NPY is injected directly into the BLA prior to the pharmacological stressor, urocortin I (Ucn; a CRF receptor agonist) or the emotional stressor, restraint. The animals that underwent restraint were evaluated in the social interaction (SI) test, while those injected with Ucn into the BLA were assessed in the two floor choice test, a modified version of the conditioned-place avoidance paradigm. The results showed that injections of NPY into the BLA prior to Ucn significantly blocked the development of the avoidance behavior in the two floor choice test and the decrease in SI time that is usually seen following restraint stress. These results provide further support that an interaction between NPY and CRF within the BLA may be critical for maintaining a normal homeostatic emotional state.     

The role of information in the emission of observing responses: a test of two hypotheses

Pigeons were trained on a trial procedure in a Skinner box. Each trial began with a fixed-interval schedule. Responding on this schedule produced a stimulus and a delayed trial outcome. The stimulus signalled whether the forthcoming outcome was reinforcement or nonreinforcement. Thus, the response was an observing response. When reinforcement was the outcome on 20% of the trials, response rates in the fixed interval were higher than when reinforcement was the outcome on 80% of the trials. This result is consistent with the hypothesis that observing responses are reinforced by the information associated with the stimulus signalling reinforcement. The result seems inconsistent with the hypothesis that observing responses are also reinforced by the information associated with the stimulus signalling nonreinforcement.     

The informational constraints of behavioral distraction by unexpected sounds: The role of event information

Sounds deviating from an otherwise repeated stream of task-irrelevant auditory stimuli (deviant sounds among standard sounds) are known to capture attention and impact negatively on ongoing behavioral performance (behavioral oddball distraction). Traditional views consider such distraction as the ineluctable consequence of the deviant sounds' low probability of occurrence relative to that of the standard. Contrary to this contention, recent evidence demonstrates that distraction by deviant sounds is not obligatory and occurs only when sounds (standards and deviants), though to be ignored, act as useful warning cues by providing information as to whether and when a target stimulus is to be presented (Parmentier, Elsley, & Ljungberg, 2010). The present study aimed to extend this finding by disentangling the roles of event information (target's probability of occurrence) and temporal information (target's time of occurrence). Comparing performance in a cross-modal oddball task where standard and deviant sounds provided temporal information, event information, both, or none, we found that distraction by deviant sounds emerged when sounds conveyed event information. These results suggest that unexpected changes in a stream of sounds yield behavioral distraction to the extent that standards and deviants carry relevant goal-directed information, specifically, the likelihood of occurrence of an upcoming target. (PsycINFO Database Record (c) 2012 APA, all rights reserved).     

Physiological and behavioral concomitants of mild stress: The effects of accuracy of temporal information

Sixty human subjects were exposed to a mild auditory stress after a fixed anticipatory period during which they performed a reaction time task. Suspense subjects were correctly informed of the time of onset of stress; Surprise subjects were told to expect the stress 10 min. later than it actually occurred. Subjects were provided with elapsed time information either automatically or on demand. Suspence subjects showed larger anticipatory electrodermal responses and smaller responses to stress than Surprise subjects but the two groups did not differ in their ratings of the unpleasantness of the stress. Female subjects showed greater anticipatory responses and consistently slower reaction times than males. The data are discussed in terms of explanations of the negative preception effect.     

Dissecting adrenal and behavioral responses to stress by targeted gene inactivation in mice

To define the molecular pathways modulating adrenal and behavioral responses to stress, we have generated mice with inactivation of hypothalamic neuropeptides and signaling pathways. Studies in mice deficient in corticotropin-releasing hormone (CRH) have revealed the essential role for CRH in adrenal glucocorticoid production in response to many physiological and psychological stressors. Immune system activation in CRH-deficient mice provides a unique exception to the necessity for CRH in stimulating adrenal glucocorticoid production. By analyzing mice deficient in interleukin-6 (IL-6) and CRH, we find that restoration of glucocorticoid output with inflammation is largely mediated by dysregulated IL-6 production. Current studies focus on identifying cellular and gene targets by which glucocorticoids regulate immune system function. In contrast to impaired adrenocortical responses to stress, CRH-deficient mice exhibit normal behavioral responses to stress. To determine signaling pathways that may contribute to the behavioral responses to stress, we have generated and analyzed mice deficient in adenylyl cyclase type 8 (AC8). AC8 deficient mice have intact adrenocortical responses to stress, but an inability to undergo stress-induced alterations in behavior.     

The role of behavioral experience in judging risks.

This study used conditional risk assessments to examine the role of behavioral experiences in risk judgments. Adolescents and young adults (ages 10-30; N = 577) were surveyed on their risk judgments for natural hazards and behavior-linked risks, including their personal experiences with these events. Results indicated that participants who had experienced a natural disaster or engaged in a particular risk behavior estimated their chance of experiencing a negative outcome resulting from that event or behavior as less likely than individuals without such experience. These findings challenge the notion that risk judgments motivate behavior and instead suggest that risk judgments may be reflective of behavioral experiences. The results have implications for health education and risk communication.     

Lipid reactivity to stress: II. Biological and behavioral influences.

This study examined behavioral and physiological influences on lipid concentrations during acute and chronic stressors. One hundred men (n = 92) and women (n = 8) were tested during a chronic stressor and during 2 acute stressors. During chronic stress, diet, physical activity, exercise, and sleep were examined. During the acute stressors, catecholamines, cortisol, plasma volume, and cardiovascular responses were examined. None of the behavioral influences could explain the lipid response to chronic stress. Responses of the atherogenic lipids to acute stressors were not solely reflecting hemoconcentration of the plasma but were moderately correlated with cardiovascular, epinephrine, and cortisol reactivity. Diastolic blood pressure reactors to the acute stressors had larger lipid responses to the chronic stressor than did nonreactors. Elevations in blood lipids during stress are not artifacts and may be clinically significant.     

The role of neuroticism on psychological and physiological stress responses

This study examined the influence of personality on stressor appraisals and emotional, physiological, and behavioral responses to psychosocial stress. Appraisals were used to classify participants as threatened (they believed their coping resources were inadequate relative to stressor demands) or challenged (they believed their coping resources were commensurate with stressor demands). Neuroticism predicted threat appraisals, and both were related to negative emotional experience and poor task performance. The influence of neuroticism on negative emotions and poor performance was mediated by threat appraisals. High neuroticism confers stress vulnerability, but only when conditions are construed as threatening.     

Individual difference in anticipatory physiological responses to signaled stress: role of locus of control and autonomic balance.

Anticipatory cardiac activity to a signaled stressful event was hypothesized to be related to individual differences in locus of control and to autonomic balance. Subjects experienced 5 trials of a 105-db burst of white noise that was signaled by a milder tone. Significant increases in electrodermal as well as heart-rate responses occurred after the stress tone. While anticipating stress, the 10 subjects designated as having high levels of coherence between heart-rate and respiratory activity (high parasympathetic balance) showed reduced heart-rate and respiratory activity (high parasympathetic balance) showed reduced heart-rate variability over the 10 subjects with low coherence. Locus of control was not related to anticipatory activity. Anticipatory cardiac activity is discussed in light of two current psychophysiological models of attention.     

The role of stress mindset in shaping cognitive,emotional, and physiological responses to challenging and threatening stress

Background and objectives: Prior research suggests that altering situation-specific evaluations of stress as challenging versus threatening can improve responses to stress. The aim of the current study was to explore whether cognitive, physiological and affective stress responses can be altered independent of situation-specific evaluations by changing individuals’ mindsets about the nature of stress in general.

Design: Using a 2?×?2 design, we experimentally manipulated stress mindset using multi-media film clips orienting participants (N?=?113) to either the enhancing or debilitating nature of stress. We also manipulated challenge and threat evaluations by providing positive or negative feedback to participants during a social stress test.

Results: Results revealed that under both threat and challenge stress evaluations, a stress-is-enhancing mindset produced sharper increases in anabolic (“growth”) hormones relative to a stress-is-debilitating mindset. Furthermore, when the stress was evaluated as a challenge, a stress-is-enhancing mindset produced sharper increases in positive affect, heightened attentional bias towards positive stimuli, and greater cognitive flexibility, whereas a stress-is-debilitating mindset produced worse cognitive and affective outcomes.

Conclusions: These findings advance stress management theory and practice by demonstrating that a short manipulation designed to generate a stress-is-enhancing mindset can improve responses to both challenging and threatening stress.     

Employee adjustment to stress: The role of coping resources, situational factors, and coping responses

Abstract The present study was designed to examine further the stress-adjustment relationship in employees. Specifically, the relations among employees' coping resources (self-esteem, generalized control beliefs, neuroticism, and social support), their appraisals of a recent stressful event experienced at work (appraised stress, self-efficacy, and situational control beliefs), the coping strategies (problem- and emotion-focused coping) used to deal with the event, and levels of employee adjustment (psychological well-being and job satisfaction) were examined. Data were collected from 153 male and female employees in a public sector department, employed in a range of middle-management administrative activities. The data provided support for a modified version of a model that proposed that both situational appraisals and coping strategies are mediating processes in the stress-adjustment relationship. There was evidence that employees' coping responses to the recent stressful event experienced at work were related to concurrent levels of adjustment. As predicted, the use of problem-focused coping, in general, had positive relationships with the measures of adjustment, whereas the effects of emotion-focused coping were generally negative (there was, however, some evidence that the effects of coping were dependent on event controllability). There was also evidence that coping resources had both direct and indirect effects (via coping and via situational appraisals) on employee adjustment. The latter effects were most marked for generalized control beliefs and self-esteem. Situational appraisals (in particular, efficacy expectancies) also had indirect effects on employee adjustment, through their effects on coping responses.     

Zinc-induced peripheral anosmia and behavioral responses to novelty in mice: a quantitative-genetic analysis

Adult male mice were made anosmic by intranasal flushing with a 5% zinc sulfate solution. Twelve behavioral variables were measured in treated as well as saline-irrigated control animals placed in a novel environment. The genetic underpinnings and the genotype-treatment interactions with regard to these behaviors were analyzed in a classical Mendelian cross between the inbred strains C57BL/6 and DBA/2 and in a full 4 X 4 diallel cross, replicated five times, between these strains and strains C3H/St an CPB-K. Based on the hypothesis of an evolutionary history of directional selection for a well-balanced information-processing system, one might expect directional dominance for decrease in exploration after anosmization. Although decreases were found for several behavioral phenotypes, only few and relatively unimportant genotype-treatment interactions were present. This absence of any kind of genetic variation for behavioral change after anosmization points to an extremely strong directional selection which has eliminated all less favorable alleles. The findings support the hypothesis of directional selection for an efficient olfactory information-processing system.     

Epileptic tendencies in relation to behavioral responses to a novel environment in the Mongolian gerbil

The severity of epileptic-like seizures in gerbils (Meriones unguiculatus), placed in an open field, is directly related to their ambulatory activity on subsequent trials. An inverse relationship, however, occurs between seizure severity and oriented, bipedal rearing behavior on subsequent trials. Principal components and multiple linear regression analyses support the hypothesis that ambulation and rearing have different underlying neuronal mechanisms. If these two activities are considered as measures of arousal and attention, respectively, then epileptic-like seizures may be caused by hyperactivity of mechanisms which induce arousal.     

Baroreflex responses to the stress of severe hemorrhage in the rat.

In two groups of anesthetized (sodium pentobarbital), mature Sprague-Dawley rats, 1) aged 2 years and weighing 300-400 grams, 2) aged 6 months weighing 200-300 grams, baroreflex-induced circulatory responses to pressor (graded doses phenylephrine) and depressor (graded doses nitroglycerine) agents were compared to those occurring during progressive hemorrhage in the same animals. Graded withdrawals of blood from the femoral artery elicited progressive hypotension accompanied by bradycardia rather than expected tachycardia. Graded doses of phenylephrine (2.5 ug to 40 ug bolus, via femoral vein) regularly induced elevations in arterial blood pressure with associated reflex bradycardia. Similarly graded doses of nitroglycerine induced a marked decline in arterial blood pressure, without expected tachycardia. As hypotension became more severe (during hemorrhage), atrioventricular conduction slowed and A-V block developed, resulting in statistically greater slowing in ventricular than in atrial excitation and contractile cycles. Heart failure during hemorrhage in the rat is characterized sequentially by severe bradycardia, depressed atrial contractile force, impaired conduction and A-V block, terminating in ventricular, atrial, and finally, in pacemaker failure. Baroreceptor reflexes were blunted or even absent in both young and old animals during induced hypotension.     

Close partner as sculptor of the ideal self: behavioral affirmation and the Michelangelo phenomenon.

This work incorporates concepts from the behavioral confirmation tradition, self tradition, and interdependence tradition to identify an interpersonal process termed the Michelangelo phenomenon. The Michelangelo phenomenon describes the means by which the self is shaped by a close partner's perceptions and behavior. Specifically, self movement toward the ideal self is described as a product of partner affirmation, or the degree to which a partner's perceptions of the self and behavior toward the self are congruent with the self's ideal. The results of 4 studies revealed strong associations between perceived partner affirmation and self movement toward the ideal self, using a variety of participant populations and measurement methods. In addition, perceived partner affirmation--particularly perceived partner behavioral affirmation--was strongly associated with quality of couple functioning and stability in ongoing relationships.     

The role of autopecking in behavioral contrast

Four groups of four pigeons each were studied on two different multiple schedules. The cues correlated with the schedule components were localized on the response key for two groups and were not localized for the others. Two groups worked on multiple schedules with variable interval 15-sec in both components, and variable interval 15-sec in one component and extinction in the other. The other two groups had identical procedures except that food was presented on a response-independent variable-time schedule. Variable-interval birds with localized stimuli showed marked behavioral contrast; variable-interval birds with non-localized stimuli showed no behavioral contrast. Variable-time birds with key-light stimuli acquired high rates of autopecking, which changed as treatment changed in a manner that paralleled rate changes, resulting in behavioral contrast for variable-interval birds. Variable-time birds with non-localized stimuli key pecked only at a low rate. The findings indicate that behavioral contrast in pigeons may result from the autopecking that is obtained with stimulus-contingent food presentation.