Differential effects of CRH infusion into the central nucleus of the amygdala in the Roman high-avoidance and low-avoidance rats

Pharmacological and Physiological Correlates of the Bidirectional Fear Phenotype of the Carioca Rats and Other Bidirectionally Selected Lines

The Carioca rat lines originated from the selective bidirectional breeding of mates displaying extreme defense responses to contextual conditioned fear. After three generations, two distinct populations could be distinguished: the Carioca High- and Low-conditioned Freezing rats, CHF, and CLF, respectively. Later studies identified strong anxiety-like behaviors in the CHF line, while indications of impulsivity and hyperactivity were prominent in the CLF animals. The present review details the physiological and pharmacological-related findings obtained from these lines. The results discussed here point towards a dysfunctional fear circuitry in CHF rats, including alterations in key brain structures and the serotoninergic system. Moreover, data from these animals highlight important alterations in the stress-processing machinery and its associated systems, such as energy metabolism and antioxidative defense. Finally, evidence of an alteration in the dopaminergic pathway in CLF rats is also debated. Thus, accumulating data gathered over the years, place the Carioca lines as significant animal models for the study of psychiatric disorders, especially fear-related ones like anxiety.

A Window on the Study of Aversive Instrumental Learning: Strains, Performance, Neuroendocrine, and Immunologic Systems

The avoidance response is present in pathological anxiety and interferes with normal daily functions. The aim of this article is to shed light on performance markers of active avoidance (AA) using two different rat strains, Sprague-Dawley (SD) and Wistar. Specifically, good and poor performers were evaluated regarding anxiety traits exhibited in the elevated plus maze (EPM) and corticosterone levels and motor activity in the open field test. In addition, the plasma levels of Interleukin-6 (IL-6), Interleukin-1Beta (IL-1beta), Nerve Growth Factor Beta (NGF-beta), Tumor Necrosis Factor-Alpha (TNF-alpha) and cytokine-induced neutrophil chemoattractant 1 (CINC-1) were compared in the good and poor performers to better understand the role of the immunologic system in aversive learning. Behavioral criteria were employed to identify subpopulations of SD and Wistar rats based on their behavioral scores during a two-way AA test. The animals were tested for anxiety-like behavior in the EPM and motor activity in the open-field test. Plasma corticosterone levels were measured at the end of the avoidance test. Cytokine levels of IL-6, IL-1beta, NGF-beta, TNF-alpha, and CINC-1 were measured in the plasma of the Wistar rats. Sixty-six percent of the Wistar rats and 35% of the SD rats exhibited a poor performance. This feature was associated with a decrease in anxiety-like behavior in the EPM. The poor and good performers exhibited lower levels of corticosterone compared with the control animals, which suggests that training alters corticosterone levels, thereby leading to hypocortisolism, independent of the performance. The CINC-1 levels were increased in the poor performers, which reinforces the role of immunologic system activation in learning deficits. Our study provides a better understanding of the complex interactions that underlie neuroimmune consequences and their implications for performance.

Effect of Stress-free Therapy on Cerebral Blood Flow: Comparisons among patients with metabolic cardiovascular disease, healthy subjects and placebo-treated subjects

BACKGROUND AND AIMS

We have developed a Stress-free Therapy(®) device wherein "Pinpoint Plantar Long-wavelength Infrared Light Irradiation (PP-LILI)" increases peripheral-deep body temperature and blood flow volume and stabilizes blood pressure as well as significantly reduces stress hormones such as adrenocorticotrophic hormone and cortisol without using drugs. Moreover, we have found this therapy to significantly improve blood glucose and insulin resistance in patients with type 2 diabetes. Based on this background of clinical efficacy, we validated changes in cerebral blood flow in patients with metabolic cardiovascular disease and examined the efficacy of Stress-free Therapy(®) on cerebral blood flow as compared to that in healthy control subjects and placebo-treated patients.

RESULTS

The change in cerebral blood flow volume during 15-minute PP-LILI was 5.1 ± 1.8 mL/min in patients with metabolic cardiovascular disease, showing a significant increase (P<0.05) of 3.1 mL/min as compared with the mean blood flow value after resting for 15 minutes.

CONCLUSIONS

Our results suggested Stress-free Therapy(®) to significantly increase cerebral blood flow, possibly leading to the prevention of metabolic cardiovascular disease.

Effect of pinpoint plantar long-wavelength infrared light irradiation on subcutaneous temperature and stress markers

BACKGROUND AND AIMS

The current investigation was aimed at the development of a novel non-invasive treatment system, "pinpoint plantar long-wavelength infrared light irradiation (PP-LILI)", which may be able to relieve mental stress and reduce stress-related hormones. Materials (Subjects) and methods: We compared the subcutaneous temperature, blood pressure, the degree of secretion of stress hormones before and after pinpoint irradiations (wavelength: 8-11 μm; output: 30mW). The study enrolled 15 subjects (Japanese healthy adults; 8 males, 7 females; average age 47.8 ± 14.6 years). Two parts of the planter region were irradiated for 15 min respectively. The stress markers such as ACTH, salivary amylase and cortisol were measured. As well, core body temperature and blood pressure were analyzed before and after the irradiation.

RESULTS

A series of experiments revealed increased body temperature, decreased levels of blood pressure and stress markers described above after the irradiation.

CONCLUSIONS

These results clearly suggest that the PP-LILI system will be quite useful for relieving stress and improvement of homeostatic functions in the body.

Effect of pinpoint plantar long-wavelength infrared light irradiation on subcutaneous temperature and stress markers

BACKGROUND AND AIMS

The current investigation was aimed at the development of a novel non-invasive treatment system, "pinpoint plantar long-wavelength infrared light irradiation (PP-LILI)", which may be able to relieve mental stress and reduce stress-related hormones. Materials (Subjects) and methods: We compared the subcutaneous temperature, blood pressure, the degree of secretion of stress hormones before and after pinpoint irradiations (wavelength: 8-11 μm; output: 30mW). The study enrolled 15 subjects (Japanese healthy adults; 8 males, 7 females; average age 47.8 ± 14.6 years). Two parts of the planter region were irradiated for 15 min respectively. The stress markers such as ACTH, salivary amylase and cortisol were measured. As well, core body temperature and blood pressure were analyzed before and after the irradiation.

RESULTS

A series of experiments revealed increased body temperature, decreased levels of blood pressure and stress markers described above after the irradiation.

CONCLUSIONS

These results clearly suggest that the PP-LILI system will be quite useful for relieving stress and improvement of homeostatic functions in the body.

Active coping with stress suppresses glucose metabolism in the rat hypothalamus

We used 18F-fluorodeoxyglucose small-animal positron-emission tomography to determine whether different styles of coping with stress are associated with different patterns of neuronal activity in the hypothalamus. Adult rats were subjected to immobilization (IMO)-stress or to a non-immobilized condition for 30 min, in random order on separate days, each of which was followed by brain-scanning. Some rats in the immobilized condition were allowed to actively cope with the stress by chewing a wooden stick during IMO, while the other immobilized rats were given nothing to chew on. Voxel-based statistical analysis of the brain imaging data shows that chewing counteracted the stress-induced increased glucose uptake in the hypothalamus to the level of the non-immobilized condition. Region-of-interest analysis of the glucose uptake values further showed that chewing significantly suppressed stress-induced increased glucose uptake in the paraventricular hypothalamic nucleus and the anterior hypothalamic area but not in the lateral hypothalamus. Together with the finding that the mean plasma corticosterone concentration at the termination of the IMO was also significantly suppressed when rats had an opportunity to chew a wooden stick, our results showed that active coping by chewing inhibited the activation of the hypothalamic-pituitary-adrenal axis to reduce the endocrine stress response.

Conditional corticotropin-releasing hormone overexpression in the mouse forebrain enhances rapid eye movement sleep

Impaired sleep and enhanced stress hormone secretion are the hallmarks of stress-related disorders, including major depression. The central neuropeptide, corticotropin-releasing hormone (CRH), is a key hormone that regulates humoral and behavioral adaptation to stress. Its prolonged hypersecretion is believed to play a key role in the development and course of depressive symptoms, and is associated with sleep impairment. To investigate the specific effects of central CRH overexpression on sleep, we used conditional mouse mutants that overexpress CRH in the entire central nervous system (CRH-COE-Nes) or only in the forebrain, including limbic structures (CRH-COE-Cam). Compared with wild-type or control mice during baseline, both homozygous CRH-COE-Nes and -Cam mice showed constantly increased rapid eye movement (REM) sleep, whereas slightly suppressed non-REM sleep was detected only in CRH-COE-Nes mice during the light period. In response to 6-h sleep deprivation, elevated levels of REM sleep also became evident in heterozygous CRH-COE-Nes and -Cam mice during recovery, which was reversed by treatment with a CRH receptor type 1 (CRHR1) antagonist in heterozygous and homozygous CRH-COE-Nes mice. The peripheral stress hormone levels were not elevated at baseline, and even after sleep deprivation they were indistinguishable across genotypes. As the stress axis was not altered, sleep changes, in particular enhanced REM sleep, occurring in these models are most likely induced by the forebrain CRH through the activation of CRHR1. CRH hypersecretion in the forebrain seems to drive REM sleep, supporting the notion that enhanced REM sleep may serve as biomarker for clinical conditions associated with enhanced CRH secretion.

Corticotropin-releasing hormone receptors in the medial prefrontal cortex regulate hypothalamic-pituitary-adrenal activity and anxiety-related behavior regardless of prior stress experience

The hypothalamic-pituitary-adrenal (HPA) axis habituates, or gradually decreases its activity, with repeated exposure to the same stressor. During habituation, the HPA axis likely requires input from cortical and limbic regions involved in the processing of cognitive information that is important in coping to stress. Brain regions such as the medial prefrontal cortex (mPFC) are recognized as important in mediating these processes. The mPFC modulates stress-related behavior and some evidence suggests that the mPFC regulates acute and repeated stress-induced HPA responses. Interestingly, corticotropin-releasing hormone (CRH)-1 receptors, which integrate neuroendocrine, behavioral and autonomic responses to stress, are localized in the mPFC but have not been specifically examined with respect to HPA regulation. We hypothesized that CRH receptor activity in the mPFC contributes to stress-induced regulation of HPA activity and anxiety-related behavior and that CRH release in the mPFC may differentially regulate HPA responses in acutely compared to repeatedly stressed animals. In the present experiments, we found that blockade of CRH receptors in the mPFC with the non-selective receptor antagonist d-Phe-CRH (50 ng or 100 ng) significantly inhibited HPA responses compared to vehicle regardless of whether animals were exposed to a single, acute 30 min restraint or to the eighth 30 min restraint. We also found that intra-mPFC injections of CRH (20 ng) significantly increased anxiety-related behavior in the elevated plus maze in both acutely and repeatedly restrained groups compared to vehicle. Together, these results suggest an excitatory influence of CRH in the mPFC on stress-induced HPA activity and anxiety-related behavior regardless of prior stress experience.

Altered brain activity processing in high-anxiety rodents revealed by challenge paradigms and functional mapping

Pathological anxiety involves aberrant processing of emotional information that is hypothesized to reflect perturbations in fear/anxiety pathways. The affected neurobiological substrates in patients with different anxiety disorders are just beginning to be revealed. Important leads for this research can be derived from findings obtained in psychopathologically relevant rodent models of enhanced anxiety, by revealing where in the brain neuronal processing in response to diverse challenges is different to that in animals with lower anxiety levels. Different functional mapping methods in various rodent models, including psychogenetically selected lines or genetically modified animals, have been used for this purpose. These studies show that the divergent anxiety-related behavioral response of high-anxiety- vs. normal and/or low-anxiety rodents to emotional challenges is associated with differential neuronal activation in restricted parts of proposed fear/anxiety circuitries including brain areas thought to be important in stress, emotion and memory. The identification of neuronal populations showing differential activation depends in part on the applied emotional challenge, indicating that specific facets of elicited fear or anxiety preferentially engage particular parts of the fear/anxiety circuitry. Hence, only the use of an array of different challenges will reveal most affected brain areas. A number of the neuronal substrates identified are suggested as candidate mediators of dysfunctional brain activation in pathological anxiety. Indeed, key findings revealed in these rodent models show parallels to observations in human symptom provocation studies comparing anxiety disorder patients with healthy volunteers. Work to investigate exactly which of the changed neuronal activation patterns in high-anxiety rodents has to be modulated by therapeutic drugs to achieve effective anxiolysis and via which neurochemical pathways this can be accomplished is at its early stages but has identified a small number of promising candidates. Extending these approaches should help to provide further insight into these mechanisms, revealing new leads for therapeutic targets and strategies.

Neuropeptides in anxiety modulation

This review is focused on the involvement of neuropeptides in the modulation of physiological and pathological anxiety. Neuropeptides play a major role as endogenous modulators of complex behaviours, including anxiety-related behaviour and psychopathology, particularly due to their high number and diversity, the dynamics of release patterns in distinct brain areas and the multiple and variable modes of interneuronal communication they are involved in. Manipulations of central neuropeptidergic systems to reveal their role in anxiety (and often comorbid depression-like behaviour) include a broad spectrum of loss-of-function and gain-of-function approaches. This article concentrates on those neuropeptides for which an involvement as endogenous anxiolytic or anxiogenic modulators is well established by such complementary approaches. Particular attention is paid to corticotropin-releasing hormone (CRH) and vasopressin (AVP) which, closely linked to stress, neuroendocrine regulation, social behaviour and learning/memory, play critical roles in the regulation of anxiety-related behaviour of rodents. Provided that their neurobiology, neuroendocrinology and molecular-genetic background are well characterized, these and other neuropeptidergic systems may be promising targets for future anxiolytic strategies.

Reduced brain CRH and GR mRNA expression precedes obesity in juvenile rats bred for diet-induced obesity

To assess the role of endogenous peptides involved in stress responsivity in the development of diet-induced obesity (DIO), selectively bred DIO and diet-resistant (DR) male were weaned onto a low fat (4.5%) chow diet at 3 weeks of age and then fed either chow or a 31% fat by energy content (high energy (HE)) diet for 9 days beginning at 4 weeks of age. Regardless of diet, DIO rats gained more weight than DR rats but did not show the selective DIO weight gain trait characteristic of older DIO rats fed HE diet. At this early age, both DR and DIO rats on HE diet ate more and had higher leptin levels but gained less body weight and had lower feed efficiency (body weight gain (g)/food intake (kcal)) than their chow-fed controls. HE diet also prevented the decline in 24h urine corticosterone levels from the third to fifth week observed in chow-fed rats. Terminally, DIO rats had lower hippocampal glucocorticoid receptor (GR) and amygdalar central nucleus corticotrophin-releasing hormone (CRH) mRNA than DR rats, regardless of their diets. Taken together with prior studies in these rats, there appears to be a critical period between 3 and 5 weeks of age when DIO and DR rats are not phenotypically different and hypothalamo-pituitary-adrenal (HPA) function is rapidly changing. The reduced expression of brain GR and CRH expression at the end of this period might contribute to the propensity of DIO rats to become obese selectively on HE diet after 5 weeks of age.

Stress-induced decrease of the intestinal barrier function. The role of muscarinic receptor activation

Recently the breakdown of the barrier function of the intestinal epithelium after application of an experimental psychological and physical stress protocol in rats has been observed. Not only did smaller molecules pass from the luminal to the serosal side, but so also did larger proteins with the dimensions of luminal antigens and toxins. The increased permeability for macromolecules is primarily due to a decrease of the tightness of the zonula occludens, but an increased endocytotic uptake indicates that transcytosis is increased also. From studies of model systems it can be concluded that activation of the intracellular protein kinase C route by muscarinic receptor activation or histamine receptor activation can be one of the underlying cellular pathways. The physical pathway relaying the stress from the brain to the intestinal tract appears to be the parasympathetic branch of the autonomic nervous system. The difference in reaction of different strains suggests that coping style is an important determinant of the response of the intestinal barrier to stress.