Chronic intermittent cold stress sensitises the hypothalamic-pituitary-adrenal response to a novel acute stress by enhancing noradrenergic influence in the rat paraventricular nucleus

Chronically stressed male and female mice show a similar peripheral and central pro-inflammatory profile after an immune challenge

Although acute stressors are known for stimulating the production of glucocorticoids and pro-inflammatory cytokines in rodents, the effects of chronic stressors on cytokine levels and the activation of the hypothalamic-pituitary-adrenal (HPA) axis, especially in response to a subsequent challenge, are less clear. In this study, male and female mice were exposed to 6 weeks of chronic variable stress (CVS) and the peripheral and central levels of IL-1β, IL-6, and TNF-α, as well as the HPA axis reactivity, were measured after an acute injection of LPS. The findings indicate that the pro-inflammatory profile in the plasma, regardless of stress exposure, was similar between male and female animals, whereas there was a region-, sex-, and stress-dependent pattern in the brain. Exposure to chronic stressors blunted the HPA reactivity to the LPS challenge, indicating a modulatory effect on the stress axis responsiveness.

Wistar Kyoto rats exhibit decreased serotonin neuronal firing and increased norepinephrine burst activity but dampened hippocampal α2-adrenoceptor sensitivity

BACKGROUND

Wistar Kyoto (WKY) rats manifest abnormalities in the function of monoamine receptors and transporters, as well as levels of these neurotransmitters in the brain. The present study assessed alterations in the firing activity of serotonin (5-hydroxytryptamine [5-HT]), norepinephrine (NE), and dopamine (DA) neurons, as well as the activity of 5-HT and NE receptors and transporters in the hippocampus.

METHODS

In vivo electrophysiological recordings were conducted in male WKY and Wistar rats. Extracellular single-unit recordings of 5-HT, NE, and DA neurons were performed. Recordings of pyramidal neurons were conducted in the medial prefrontal cortex (mPFC) and the hippocampus, where direct application of 5-HT and NE by iontophoresis was also carried out.

RESULTS

The mean firing rate of 5-HT neurons was significantly decreased in WKY compared to Wistar rats. The burst activity of NE neurons was significantly increased in WKY, while their mean firing activity was not changed. There was no alteration in the firing, burst, and population activity of DA neurons in WKY animals. In the hippocampus, a decrease in sensitivity of α2-adrenoceptors, but not 5-HT receptors, was observed. There was, however, no change in the activity of 5-HT and NE transporters. The firing activity of mPFC pyramidal neurons was similar in WKY versus Wistar rats.

CONCLUSION

In WKY rats, there was a decrease in the firing activity of 5-HT neurons. There was also an enhanced burst activity of NE neurons, accompanied by a reduction in sensitivity of the α2-adrenoceptor in the hippocampus, inferring a decrease in NE transmission.

Influence of depression on the association between colder indoor temperature and higher blood pressure

OBJECTIVES

Cold exposure accounts for more than 7% of all-cause mortality worldwide, and cold-induced blood pressure (BP) elevation and consequent cardiovascular events are partially responsible. For prevention, it is important to identify risk factors for exaggerated temperature-sensitivity of BP but this is not fully understood. This study investigated whether depressive symptoms affect the relationship between indoor temperature and BP.

METHODS

We conducted a cross-sectional analysis of 1076 community-based individuals who were at least 60 years of age. Depressive symptoms were assessed using the 15-item Geriatric Depression Scale at a cutoff point of 4/5. We performed ambulatory BP monitoring and indoor temperature measurement on two consecutive days during the cold season in Nara, Japan.

RESULTS

When using daytime SBP as a dependent variable, multilevel linear regression analyses showed that lower daytime indoor temperature was significantly associated with higher daytime SBP in the depressive group (n = 216, β = -0.804, P < 0.001) but not in the nondepressive group (n = 860, β = -0.173, P = 0.120); moreover, a significant interaction between depression and daytime indoor temperature was observed (P = 0.014). These relationships were independent of potential confounders including age, gender, BMI, medications, and physical activity. Similar results were obtained for morning SBP, nocturnal SBP dipping, and morning BP surge.

CONCLUSION

The results suggest that depressive participants are more likely to have cold-induced BP elevation than nondepressive participants. Further longitudinal studies are warranted to determine whether people with depressive symptoms are at a high risk for cold-related cardiovascular events.

Neuroinflammation as an etiological trigger for depression comorbid with inflammatory bowel disease

Patients with inflammatory bowel disease (IBD) suffer from depression at higher rates than the general population. An etiological trigger of depressive symptoms is theorised to be inflammation within the central nervous system. It is believed that heightened intestinal inflammation and dysfunction of the enteric nervous system (ENS) contribute to impaired intestinal permeability, which facilitates the translocation of intestinal enterotoxins into the blood circulation. Consequently, these may compromise the immunological and physiological functioning of distant non-intestinal tissues such as the brain. In vivo models of colitis provide evidence of increased blood–brain barrier permeability and enhanced central nervous system (CNS) immune activity triggered by intestinal enterotoxins and blood-borne inflammatory mediators. Understanding the immunological, physiological, and structural changes associated with IBD and neuroinflammation may aid in the development of more tailored and suitable pharmaceutical treatment for IBD-associated depression.

In vivo demonstration of a novel non-invasive model for inducing localized hypothermia to ameliorate hepatotoxicity

Moderate hypothermia (32 °C) has been previously shown to ameliorate drug-induced liver injuries in vitro. However, there are concerns regarding its clinical relevance as it remains a challenge to perform selective liver cooling in a non-invasive manner. To reconcile this dilemma, we propose the use of pulsed cooling for regional hypothermic conditioning in liver. This involves intermittent cooling applied in pulses of 15 min each, with a one-hour recovery interval between pulses. Cooling is achieved by applying ice packs to the cutaneous region overlying the liver. Through an in vivo C57BL/6NTac mouse study, we demonstrated the feasibility of attaining localized hypothermia close to the liver while maintaining core body temperature. This has successfully ameliorated acetaminophen-induced liver injury based on the liver function tests, liver histology and total weight change. Collectively, we provide a proof of concept for pulsed external localized cooling as being clinically actionable to perform induced selective hypothermia.

Histopathological, histochemical and biochemical postmortem changes in induced fatal hypothermia in rats

Reaching a postmortem diagnosis of hypothermia is challenging in forensic practice. Therefore, this study was conducted to detect the histopathological, histochemical and biochemical changes that occur in adult albino rats following exposure to induced fatal hypothermia. Twenty-four adult albino rats were divided into the negative control, moderate hypothermia, severe hypothermia and hypoxia groups. Rats in the control group were euthanized when those in the moderate hypothermic group died. Blood samples were collected via heart puncture, and the cerebrum, heart, suprarenal gland, kidney, liver and skeletal muscle were removed to investigate the biochemical, histochemical and histopathological changes. Postmortem assessment depicted significant changes in lipid peroxidation, represented by increased malondialdehyde levels in the studied organs of the rats in hypothermic and hypoxia groups. Histopathological examination of the rats’ organs revealed degeneration and necrosis in the hypothermia and hypoxia groups. Sections taken from the severe hypothermic rats revealed a loss of normal cardiac tissue architecture, necrotic changes in the pyramidal cells in the cerebral cortex, and massive necrosis, mainly in the tubules of the renal cortex and medulla. These findings suggest that histological changes might be used as biochemical markers for postmortem diagnosing of fatal hypothermia, particularly in severe hypothermic conditions.

Key points

Death by hypothermia is a serious public health problem worldwide.

Confirming a diagnosis and determining the cause of death in cases of hypothermia are among the most difficult practices in forensic medicine.

Death by hypothermia might be associated with structural abnormalities in various organs.

Studies using different tissue staining techniques will enable an overall illustration of the role of histopathological changes in body organs as indicators of hypothermia.

Hypertension in Prenatally Undernourished Young-Adult Rats Is Maintained by Tonic Reciprocal Paraventricular-Coerulear Excitatory Interactions

Prenatally malnourished rats develop hypertension in adulthood, in part through increased α₁-adrenoceptor-mediated outflow from the paraventricular nucleus (PVN) to the sympathetic system. We studied whether both α₁-adrenoceptor-mediated noradrenergic excitatory pathways from the locus coeruleus (LC) to the PVN and their reciprocal excitatory CRFergic connections contribute to prenatal undernutrition-induced hypertension. For that purpose, we microinjected either α₁-adrenoceptor or CRH receptor agonists and/or antagonists in the PVN or the LC, respectively. We also determined the α₁-adrenoceptor density in whole hypothalamus and the expression levels of α_1A-adrenoceptor mRNA in the PVN. The results showed that: (i) agonists microinjection increased systolic blood pressure and heart rate in normotensive eutrophic rats, but not in prenatally malnourished subjects; (ii) antagonists microinjection reduced hypertension and tachycardia in undernourished rats, but not in eutrophic controls; (iii) in undernourished animals, antagonist administration to one nuclei allowed the agonists recover full efficacy in the complementary nucleus, inducing hypertension and tachycardia; (iv) early undernutrition did not modify the number of α₁-adrenoceptor binding sites in hypothalamus, but reduced the number of cells expressing α_1A-adrenoceptor mRNA in the PVN. These results support the hypothesis that systolic pressure and heart rate are increased by tonic reciprocal paraventricular-coerulear excitatory interactions in prenatally undernourished young-adult rats.

Skin damage caused by scale loss modifies the intestine of chronically stressed gilthead sea bream (Sparus aurata, L.)

The present study was designed to test if the damage caused by scale loss provokes a change in other innate immune barriers such as the intestine and how chronic stress affects this response. Sea bream (Sparus aurata) were kept in tanks at low density (16 kg m^-3, LD) or exposed to a chronic high density (45 kg m^-3, HD) stress for 4 weeks. Scales were then removed (approximately 50%) from the left flank in the LD and HD fish. Intestine samples (n = 8/group) were examined before and at 12 h, 3 days and 7 days after scale removal. Changes in the morphology of the intestine revealed that chronic stress and scale loss was associated with intestinal inflammation. Specifically, enterocyte height and the width of the lamina propria, submucosa and muscle layer were significantly increased (p < 0.05) 3 days after skin damage in fish under chronic stress (HD) compared to other treatments (LDWgut3d or HDgut0h). This was associated with a significant up-regulation (p < 0.05) in the intestine of gene transcripts for cell proliferation (pcna) and anti-inflammatory cytokine tgfβ1 and down-regulation of gene transcripts for the pro-inflammatory cytokines tnf-α and il1β (p < 0.05) in HD and LD fish 3 days after scale removal compared to the undamaged control (LDgut0h). Furthermore, a significant up-regulation of kit, a marker of mast cells, in the intestine of HDWgut3d and LDWgut3d fish suggests they may mediate the crosstalk between immune barriers. Skin damage induced an increase in cortisol levels in the anterior intestine in HDWgut12 h fish and significant (p < 0.05) down-regulation of mr expression, irrespective of stress. These results suggest glucocorticoid levels and signalling in the intestine of fish are modified by superficial cutaneous wounds and it likely modulates intestine inflammation.

Macrophage Stimulated by Low Ambient Temperature Hasten Tumor Growth via Glutamine Production

Ambient temperature can regulate the immune response and affect tumor growth. Although thermoneutral caging reduces tumor growth via immune activation, little attention has been paid to the tumorigenic effect of low temperature. In the present study, tumor growth was higher at low ambient temperature (4 °C for 8 h/d) than at the standard housing temperature (22 °C) in allograft models. Low temperature-stimulated tumor growth in mice was reduced by monocyte depletion using clodronate liposomes. Proliferation was considerably greater in cancer cells treated with 33 °C-cultured RAW264.7 cell-conditioned media (33CM) than in cells treated with 37 °C-cultured RAW264.7 cell-conditioned media (37CM). Additionally, glutamine levels were markedly higher in 33CM-treated cells than in 37CM-treated cells. We further confirmed that the addition of glutamine into 37CM enhanced its effects on cancer cell proliferation and glutamine uptake inhibition ameliorated the accelerated proliferation induced by 33CM. Consistently, the inhibition of glutamine uptake in the allograft model exposed to low temperature, effectively reduced tumor volume and weight. Collectively, these data suggest that the secretion and utilization of glutamine by macrophages and cancer cells, respectively, are key regulators of low temperature-enhanced cancer progression in the tumor microenvironment.

Expression of ADR-α1, 2 and ADR-β2 in cumulus cell culture of infertile women with polycystic ovary syndrome and poor responder who are a candidate for IVF: the novel strategic role of clonidine in this expression

OBJECTIVE

Alpha and beta-adrenoceptors (ADR-α1, 2, and β2) play a regulatory role in the folliculogenesis and steroidogenesis in the ovarian follicles. This study aimed to measure these adrenoceptors mRNA and its protein levels in cumulus cells (CCs) culture of poor ovarian reserve (POR) and polycystic ovarian syndrome (PCOS) infertile women (IVF candidate) and the effect of clonidine treatment at CCs culture.

METHODS

This case/control study was conducted in 2017 includes a control (donation oocytes) and two studies (PCO and POR) groups. The ovulation induction drugs were prescribed in all groups. After the oocyte puncture, the follicular fluid was collected and CCs were isolated were cultured. RNA was extracted and cDNA was synthesized and designed the primer for the ADR-α1, 2 and ADR-β2 gene expression. The protein levels were investigated by Western Blot.

RESULTS

The results showed a high level of three adrenergic expressions in PCO women compared to the control group (p-value <.001), which can be reduced by clonidine. POR group showed a significant decrease in the gene expression of ADR-α1 (p-value = .004) and ADR-α2 (p-value = .003) compared to the control group and clonidine treatment had no effect.

CONCLUSION

The significant increase of three adrenoceptors gene expression and protein levels in CCs culture indicate to the hyperactivity of the ovarian sympathetic nervous system at the receptor levels in women with PCOS, and clonidine confirmed it by reducing this expression. In POR women, the reduction of ADR-α1, 2 expressions maybe lead to the aging process in the ovary.

Amelioration effects of Kaempferol on immune response following chronic intermittent cold-stress

Cold-stress causes disturbance of the homeostatic regulation of animals, and gradually impairs the immune and antioxidant functions of animals. Therefore, increasing the effectiveness of the immune response and antioxidant function are the most attractive strategies against cold-stress. Kaempferol (KPF) exerts both an anti-inflammatory and antioxidant pharmacological effect. However, nor much is known of the effects of KPF on providing protection from cold-induced intestinal oxidative damage and improving immunity. This study investigated the effects of KPF on immune factors and intestinal antioxidation in the blood of cold-stressed mice. KPF was solubilized in diluted saline before administration. The mice were randomly divided into 4 groups: (1) control, (2) cold-stress, (3) KPF 25 mg/kg, and (4) cinnamon (CAM) 30 mg/kg groups. Groups (2)-(4) were exposed to cold stress once a day for 7 days. Cold-stress was achieved by exposing the mice to a temperature of -15 °C and 70 ± 10% humidity for 60 min, once a day. The histopathological changes in the small intestine of the mice were analyzed. The T lymphocyte populations in blood were measured using flow cytometry. The level of SLC6a4, 5-HT3 and 5-HTT in small intestine tissue was assessed using RT-PCR analysis. Cow blood samples were obtained for the hematological analysis. Kaempferol (KPF) (25 mg/kg) regularized the intestinal antioxidant activity in the cold stress animals. KPF was able to significantly (P < .05) return intestinal SLC6a4, 5-HT3 and 5-HTT levels to normal after it had increased due to cold-stress. KPF treatment prevented the cold stress-induced decrease in blood CD4⁺T cells and decrease CD8⁺T cells levels in mice. Improved hematological profiles were additionally observed on treatment cows with KPF. KPF compared favorably with cinnamon in cold stress management, suggesting cold stress disturbs the anti-inflammatory effect of KPF. Thus, KPF contributes to suppress the activated pro-inflammatory cytokines, IL-9, IL-13, CD8⁺T and neurochemicals, and to increase anti-inflammatory cytokines and CD4⁺T levels.

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.

Chronic cold exposure results in subcutaneous adipose tissue browning and altered global metabolism in Qinghai-Tibetan plateau pika (Ochotona curzoniae)

The plateau pika (Ochotona curzoniae), one of the indigenous animals of the Qinghai-Tibet Plateau, is adapted to life in a cold and hypoxic environment. We conducted a series of genomic, proteomic and morphological studies to investigate whether changes in energy metabolism contribute to adaptation of the plateau pika to cold stress by analyzing summer and winter cohorts. The winter group showed strong morphological and histological features of brown adipose tissue (BAT) in subcutaneous white adipose tissue (sWAT). To obtain molecular evidence of browning of sWAT, we performed reverse transcription and quantitative real-time PCR, which revealed that BAT-specific genes, including uncoupling protein 1 (UCP-1) and PPAR-γ coactivator 1α (PGC-1α), were highly expressed in sWAT from the winter group. Compared with the summer group, Western blot analysis also confirmed that UCP-1, PGC-1α and Cox4 protein levels were significantly increased in sWAT from the winter group. Increased BAT mass in the inter-scapular region of the winter group was also observed. These results suggest that the plateau pika adapts to cold by browning sWAT and increasing BAT in order to increase thermogenesis. These changes are distinct from the previously reported adaptation of highland deer mice. Understanding the regulatory mechanisms underlying this adaptation may lead to novel therapeutic strategies for treating obesity and metabolic disorders.

Inhibitory effects of Aconiti Lateralis Radix Preparata on chronic intermittent cold-induced inflammation in the mouse hypothalamus

ETHNOPHARMACOLOGICAL RELEVANCE

Aconiti Lateralis Radix Preparata (AR) is the most frequently used herb to generate heat and treat symptoms associated with coldness in Asia.

AIMS OF THE STUDY

The hypothalamus is one of the master regulators to maintain constant core body temperature. Chronic exposure to cold stress disturbs homeostatic regulation, gradually resulting in hypothalamic inflammation. This study investigate the effects of AR, on the chronic intermittent cold (CIC)-induced release of pro-inflammatory signaling molecules in the mouse hypothalamus.

MATERIALS AND METHODS

Aconiti Lateralis Radix Preparata extract (ARE) were solubilized in distilled water and diluted with saline before administration. Male ICR mice (7 weeks old, 30-32g) were divided randomly into 6 groups: (1) control, (2) cold stress, (3) ARE 30, (4) ARE 100, (5) ARE 300, and (6) ARE 1000mg/kg groups. Groups (2)-(6) were exposed to CIC stress once a day for 14 days. CIC stress was achieved by exposing the mice to 4°C and 60 ± 10% humidity for 120min once a day. Rectal temperature was measured after terminating cold stress. Cortisol levels were measured from serum. Hypothalamus tissue was used for western blot analysis, and IL-9, IL-13, PGE1, and PGE2 levels were assessed.

RESULTS

ARE treatment prevented the CIC-induced decrease in rectal temperature and increase in serum cortisol level. ARE-treated CIC-exposed mice demonstrated decrease in nuclear c-Fos levels dose-dependently compared to CIC-exposed mice. Nuclear NF-kB expression showed significant increase in CIC-exposed mice. ARE treatment significantly blunted the increase in nuclear NF-kB expression. CIC-exposed mice had significantly increased levels of both IL-9 and IL-13. Treatment with ARE suppressed the elevated IL-9 and IL-13 levels. Between control and CIC-exposed mice PGE1 levels showed no difference. However ARE (1000mg/kg)-treated CIC-exposed mice had a significant increase in PGE1 level compared to CIC-exposed mice. PGE2 levels were significantly higher in CIC-exposed mice compared to control mice. ARE treatment significantly attenuated the increase in PGE2 levels.

CONCLUSIONS

Our findings suggest CIC stress disturbs the anti-inflammatory effect of cortisol and maintenance of the body temperature. Thus AR contributes to suppress the activated proinflammatory factors, IL-9, IL-13, and PGE-2, and to increase the heat production.

Regulation of Hypothalamo-Pituitary-Adrenocortical Responses to Stressors by the Nucleus of the Solitary Tract/Dorsal Vagal Complex

Hindbrain neurons in the nucleus of the solitary tract (NTS) are critical for regulation of hypothalamo-pituitary-adrenocortical (HPA) responses to stress. It is well known that noradrenergic (as well as adrenergic) neurons in the NTS send direct projections to hypophysiotropic corticotropin-releasing hormone (CRH) neurons and control activation of HPA axis responses to acute systemic (but not psychogenic) stressors. Norepinephrine (NE) signaling via alpha1 receptors is primarily excitatory, working either directly on CRH neurons or through presynaptic activation of glutamate release. However, there is also evidence for NE inhibition of CRH neurons (possibly via beta receptors), an effect that may occur at higher levels of stimulation, suggesting that NE effects on the HPA axis may be context-dependent. Lesions of ascending NE inputs to the paraventricular nucleus attenuate stress-induced ACTH but not corticosterone release after chronic stress, indicating reduction in central HPA drive and increased adrenal sensitivity. Non-catecholaminergic NTS glucagon-like peptide 1/glutamate neurons play a broader role in stress regulation, being important in HPA activation to both systemic and psychogenic stressors as well as HPA axis sensitization under conditions of chronic stress. Overall, the data highlight the importance of the NTS as a key regulatory node for coordination of acute and chronic stress.

Interoceptive modulation of neuroendocrine, emotional, and hypophagic responses to stress

Periods of caloric deficit substantially attenuate many centrally mediated responses to acute stress, including neural drive to the hypothalamic-pituitary-adrenal (HPA) axis, anxiety-like behavior, and stress-induced suppression of food intake (i.e., stress hypophagia). It is posited that this stress response plasticity supports food foraging and promotes intake during periods of negative energy balance, even in the face of other internal or external threats, thereby increasing the likelihood that energy stores are repleted. The mechanisms by which caloric deficit alters central stress responses, however, remain unclear. The caudal brainstem contains two distinct populations of stress-recruited neurons [i.e., noradrenergic neurons of the A2 cell group that co-express prolactin-releasing peptide (PrRP+ A2 neurons), and glucagon-like peptide 1 (GLP-1) neurons] that also are responsive to interoceptive feedback about feeding and metabolic status. A2/PrRP and GLP-1 neurons have been implicated anatomically and functionally in the central control of the HPA axis, anxiety-like behavior, and stress hypophagia. The current review summarizes a growing body of evidence that caloric deficits attenuate physiological and behavioral responses to acute stress as a consequence of reduced recruitment of PrRP+ A2 and hindbrain GLP-1 neurons, accompanied by reduced signaling to their brainstem, hypothalamic, and limbic forebrain targets.

Optimizing laboratory animal stress paradigms: The H-H* experimental design

Major advances in behavioral neuroscience have been facilitated by the development of consistent and highly reproducible experimental paradigms that have been widely adopted. In contrast, many different experimental approaches have been employed to expose laboratory mice and rats to acute versus chronic intermittent stress. An argument is advanced in this review that more consistent approaches to the design of chronic intermittent stress experiments would provide greater reproducibility of results across laboratories and greater reliability relating to various neural, endocrine, immune, genetic, and behavioral adaptations. As an example, the H-H* experimental design incorporates control, homotypic (H), and heterotypic (H*) groups and allows for comparisons across groups, where each animal is exposed to the same stressor, but that stressor has vastly different biological and behavioral effects depending upon each animal's prior stress history. Implementation of the H-H* experimental paradigm makes possible a delineation of transcriptional changes and neural, endocrine, and immune pathways that are activated in precisely defined stressor contexts.

Learning about stress: neural, endocrine and behavioral adaptations

In this review, nonassociative learning is advanced as an organizing principle to draw together findings from both sympathetic-adrenal medullary and hypothalamic-pituitary-adrenocortical (HPA) axis responses to chronic intermittent exposure to a variety of stressors. Studies of habituation, facilitation and sensitization of stress effector systems are reviewed and linked to an animal's prior experience with a given stressor, the intensity of the stressor and the appraisal by the animal of its ability to mobilize physiological systems to adapt to the stressor. Brain pathways that regulate physiological and behavioral responses to stress are discussed, especially in light of their regulation of nonassociative processes in chronic intermittent stress. These findings may have special relevance to various psychiatric diseases, including depression and post-traumatic stress disorder (PTSD).

Association Between Ambient Temperature and Lower Urinary Tract Symptoms: A Hospital-Based Cross-Sectional Analysis

OBJECTIVES

To date, there is no overall agreement as to risk of ambient temperature for lower urinary tract symptoms (LUTS) due to benign prostatic hyperplasia (BPH). Thus, we focused on ambient temperature as an environmental factor affecting LUTS and attempted to explain the temperature differences in LUTS severity in cases in real clinical practice.

METHODS

This was a multicenter, cross-sectional survey. The study involved 1612 men aged 40 years and older who visited 23 university hospitals in 10 major areas in South Korea between September 2010 and December 2011. The participants who had good overall mental and physical health, and complaint of LUTS were included. Korea Meteorological Administration data were used to determine daily average temperatures and daily temperatures on the interview dates at each site.

RESULTS

The average age of the 1612 men was 66.57 ± 10.03 years. The mean International Prostate Symptom Score (IPSS) and symptom duration were 18.51 ± 6.77 and 3.79 ± 3.89 years, respectively. Daily average temperature and temperature difference ranged from -13.1 to 28.5 °C and 0 to 20.6 °C, respectively. Age was a significant risk factor for IPSS, symptom duration, prostate volume (PV), maximal urinary flow rate (Qmax), average urinary flow rate (Qave) and total voiding volume (P < 0.001) but not QOL. Logistic regression analysis after adjustment for age and PV revealed that Qave and total voiding volume were increased as the temperature declined. However, IPSS and Qmax did not show a statistically significant difference as the temperature declined.

CONCLUSION

Our findings did not demonstrate an increased clinically significant risk of LUTS severity in connection with ambient temperature in clinical practice.

Ascending mechanisms of stress integration: Implications for brainstem regulation of neuroendocrine and behavioral stress responses

In response to stress, defined as a real or perceived threat to homeostasis or well-being, brain systems initiate divergent physiological and behavioral processes that mobilize energy and promote adaptation. The brainstem contains multiple nuclei that engage in autonomic control and reflexive responses to systemic stressors. However, brainstem nuclei also play an important role in neuroendocrine responses to psychogenic stressors mediated by the hypothalamic-pituitary-adrenocortical axis. Further, these nuclei integrate neuroendocrine responses with stress-related behaviors, significantly impacting mood and anxiety. The current review focuses on the prominent brainstem monosynaptic inputs to the endocrine paraventricular hypothalamic nucleus (PVN), including the periaqueductal gray, raphe nuclei, parabrachial nuclei, locus coeruleus, and nucleus of the solitary tract (NTS). The NTS is a particularly intriguing area, as the region contains multiple cell groups that provide neurochemically-distinct inputs to the PVN. Furthermore, the NTS, under regulatory control by glucocorticoid-mediated feedback, integrates affective processes with physiological status to regulate stress responding. Collectively, these brainstem circuits represent an important avenue for delineating interactions between stress and health.

Inter-relation between autonomic and HPA axis activity in children and adolescents

Stress research in youth typically considers either the autonomic nervous system or HPA axis. However, these systems are highly coordinated and physically interconnected. We examined whether the inter-relation between cardio-autonomic and HPA axis measures was better associated with perceived stress than their singular associations. Children and adolescents (N=201) collected saliva samples to measure cortisol (AUCAG, AUCI, maximum), wore an electrocardiogram monitor for 24h to derive heart rate variability (HRV; LF, HF, LF/HF ratio), and completed the Perceived Stress Scale. The interaction between sympathovagal modulation (LF, LF/HF ratio) and cortisol awakening response (AUCAG, AUCI, maximum) explained significantly greater variance in perceived stress than either stress system alone. Higher sympathovagal modulation combined with higher cortisol awakening response was associated with greater perceived stress. Findings suggest that the inter-relation between cardio-autonomic and HPA axis activity may advance our understanding of how stress impacts health.

Stress-related synaptic plasticity in the hypothalamus

Stress necessitates an immediate engagement of multiple neural and endocrine systems. However, exposure to a single stressor causes adaptive changes that modify responses to subsequent stressors. Recent studies examining synapses onto neuroendocrine cells in the paraventricular nucleus of the hypothalamus demonstrate that stressful experiences leave indelible marks that alter the ability of these synapses to undergo plasticity. These adaptations include a unique form of metaplasticity at glutamatergic synapses, bidirectional changes in endocannabinoid signalling and bidirectional changes in strength at GABAergic synapses that rely on distinct temporal windows following stress. This rich repertoire of plasticity is likely to represent an important building block for dynamic, experience-dependent modulation of neuroendocrine stress adaptation.

Norepinephrine and corticosterone in the medial prefrontal cortex and hippocampus predict PTSD-like symptoms in mice

This study measured changes in brain extracellular norepinephrine (NE) and free corticosterone (CORT) levels in a mouse model of post-traumatic stress disorder and related them to hyperarousal and fear memory retention. To this end, microdialysis in the medial prefrontal cortex (mPFC) and the hippocampus (HPC) of male C57BL/6NCrl mice was performed during an acoustic startle response (ASR) and following an electric foot shock (FS), as well as during an ASR and recall of contextual fear (CF) 1 day later. Changes in ASR-stimulated NE levels in the mPFC corresponded to ASR 34 days after FS. Changes in basal and ASR-stimulated extracellular NE levels in the HPC, in contrast, were related to expression of early (day 2) and late (day 34) CF after FS. The increase in extracellular NE levels correlated in a U-shape manner with arousal levels and CF, thus suggesting a non-direct relationship. Stress of different modalities/strength (ASR, FS and CF) caused a similar relative increase in free CORT levels both in the mPFC and the HPC. One day after FS, ASR-induced increases in the CORT content in the mPFC tended to correlate with the FS-potentiated ASR in a U-shape manner. Taken together, these data show that the intracerebral increase in free CORT was likely related to an immediate response to stress, whereas NE neurotransmission in the forebrain predicted arousal and CF 1 month after trauma.

Intermittent cold exposure results in visceral adipose tissue "browning" in the plateau pika (Ochotona curzoniae)

The plateau pika has developed tolerance to cold and hypoxia in order to adapt to living in the extreme environment of the Qinghai-Tibetan Plateau. One mammalian mechanism for cold adaptation is thermogenesis by brown adipose tissue (BAT), but the degree to which pika exploits this mechanism or how it may be modified by the additional stresses of high altitude is not known. Intermittent Cold Exposure (ICE) is an approachable method to study cold adaptation in rodents. To investigate the role of adipose tissue in the adaptation of pika to cold temperatures, we have studied pika during ICE. We find that pika kept in warm temperatures has little classical brown fat, but "browning" of white adipose tissues is observed rapidly upon cold exposure. This is demonstrated by the increased expression of several markers of brown fat differentiation including uncoupling protein 1 (UCP-1). Surprisingly, this occurs mainly in visceral rather than epididymal adipose tissue. In addition, ICE increases the expression of several general adipose differentiation markers at both the mRNA and protein levels. These substantial changes in the distribution of fat are accomplished without changes in weight or blood levels of glucose and triglycerides, suggesting that the adaptable changes are coordinated and self-compensated. Together, our results demonstrate that ICE promotes recruitment of BAT in pika, and unlike small mammals in at lower altitudes, pika can activate visceral WAT to adapt to cold stress without major changes overall energy balance.

Stress-induced sensitization: the hypothalamic-pituitary-adrenal axis and beyond

Exposure to certain acute and chronic stressors results in an immediate behavioral and physiological response to the situation followed by a period of days when cross-sensitization to further novel stressors is observed. Cross-sensitization affects to different behavioral and physiological systems, more particularly to the hypothalamus-pituitary-adrenal (HPA) axis. It appears that the nature of the initial (triggering) stressor plays a major role, HPA cross-sensitization being more widely observed with systemic or high-intensity emotional stressors. Less important appears to be the nature of the novel (challenging) stressor, although HPA cross-sensitization is better observed with short duration (5-15 min) challenging stressors. In some studies with acute immune stressors, HPA sensitization appears to develop over time (incubation), but most results indicate a strong initial sensitization that progressively declines over the days. Sensitization can affect other physiological system (i.e. plasma catecholamines, brain monoamines), but it is not a general phenomenon. When studied concurrently, behavioral sensitization appears to persist longer than that of the HPA axis, a finding of interest regarding long-term consequences of traumatic stress. In many cases, behavioral and physiological consequences of prior stress can only be observed following imposition of a new stressor, suggesting long-term latent effects of the initial exposure.

Facilitation of the HPA axis to a novel acute stress following chronic stress exposure modulates histone acetylation and the ERK/MAPK pathway in the dentate gyrus of male rats

Evidence suggests that when presented with novel acute stress, animals previously exposed to chronic homotypic or heterotypic stressors exhibit normal or enhanced hypothalamic-pituitary-adrenal (HPA) response compared with animals exposed solely to that acute stressor. The molecular mechanisms involved in this effect remain unknown. The extracellular signal-regulated kinase (ERK) is one of the key pathways regulated in the hippocampus in both acute and chronic stress. The aim of this study was to examine the interaction of prior chronic stress, using the chronic variable stress model (CVS), with exposure to a novel acute stressor (2,5-dihydro-2,4,5-trimethyl thiazoline; TMT) on ERK activation, expression of the downstream protein BCL-2, and the glucocorticoid receptor co-chaperone BAG-1 in control and chronically stressed male rats. TMT exposure after chronic stress resulted in a significant interaction of chronic and acute stress in all 3 hippocampus subregions on ERK activation and BCL-2 expression. Significantly, acute stress increased ERK activation, BCL-2 and BAG-1 protein expression in the dentate gyrus (DG) of CVS-treated rats compared with control, CVS-treated alone, and TMT-only animals. Furthermore, CVS significantly increased ERK activation in medial prefrontal cortex, but acute stress had no significant effect. Inhibition of corticosterone synthesis with metyrapone had no significant effect on ERK activation in the hippocampus; therefore, glucocorticoids alone do not mediate the molecular effects. Finally, because post-translational modifications of histones are believed to play an important role in the stress response, we examined changes in histone acetylation. We found that, in general, chronic stress decreased K12H4 acetylation, whereas acute stress increased acetylation. These results indicate a molecular mechanism by which chronic stress-induced HPA axis plasticity can lead to neurochemical alterations in the hippocampus that influence reactivity to subsequent stress exposure. This may represent an important site of dysfunction that contributes to stress-induced pathology such as depression, anxiety disorders, and posttraumatic stress disorder.

Beyond inhibition: GABA synapses tune the neuroendocrine stress axis

We recently described a novel form of stress-associated bidirectional plasticity at GABA synapses onto hypothalamic parvocellular neuroendocrine cells (PNCs), the apex of the hypothalamus-pituitary-adrenal axis. This plasticity may contribute to neuroendocrine adaptation. However, this GABA synapse plasticity likely does not translate into a simple more and less of inhibition because the ionic driving force for Cl(-) , the primary charge carrier for GABAA receptors, is dynamic. Specifically, stress impairs a Cl(-) extrusion mechanism in PNCs. This not only renders the steady-state GABA response less hyperpolarizing but also makes PNCs susceptible to the activity-dependent accumulation of Cl(-) . Accordingly, GABA synapse plasticity impacts both the robustness of GABA voltage response and dynamic Cl(-) loading, imposing nonlinear influences on PNC excitability during circuit activities. This theoretical consideration predicts roles for GABA transmission far more versatile than canonical inhibition. We propose potential impacts of GABA synapse plasticity on the experience-dependent fine-tuning of neuroendocrine stress responses.

Involvement of magnitude of ambient temperature change in nonspecific effect in perceived placebo effect on lower urinary tract symptoms: study on switching of naftopidil in patients with benign prostatic hyperplasia

PURPOSE

To determine if switching from one brand of the α1-adrenoceptor antagonist naftopidil (Avishot™) to another brand (Flivas™) under the same conditions causes the same changes in lower urinary tract symptoms (LUTS) and quality of life (QOL) as the perceived placebo effect, and if ambient temperature as a nonspecific factor is related to those changes in benign prostatic hyperplasia (BPH) patients.

PATIENTS AND METHODS

A retrospective study was carried out on 217 BPH patients who had received Avishot™ for more than 6 months and then were switched to Flivas™ at the same dose and timing. The two drugs contain the same principal ingredient and display the same pharmacokinetic properties. The International Prostate Symptom Score (IPSS), QOL score, and average monthly ambient temperature at the patients' residence area from the Automated Meteorological Data Acquisition System in Japan were used for the evaluation.

RESULTS

A significant change in urinary storage symptoms (P = 0.006), and especially in nighttime frequency (P< 0.001), was observed by switching drugs, suggesting the perceived placebo effect. There was significant improvement of daytime frequency (P< 0.05), nighttime frequency (P< 0.001), storage symptoms (P< 0.001), and total IPSS (P< 0.05) when the magnitude of ambient temperature change from before and 3 months after switching drugs was higher than 10°C, while no significant improvement was noted in any of the parameters examined when the same was lower than 10°C.

CONCLUSION

The present study showed the nonspecific effect of magnitude of ambient temperature change was involved in the perceived placebo effect on LUTS, especially on storage symptoms, by switching drugs. The nonspecific effect on LUTS with BPH needs to be considered when evaluating subjective treatment efficacy of drugs for LUTS with BPH in routine clinical practice. The present study supports the lifestyle advice "avoid exposing the lower body to cold temperature" or "keep warm when it is cold" for LUTS with BPH.

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.

Neural control of chronic stress adaptation

Stress initiates adaptive processes that allow the organism to physiologically cope with prolonged or intermittent exposure to real or perceived threats. A major component of this response is repeated activation of glucocorticoid secretion by the hypothalamo-pituitary-adrenocortical (HPA) axis, which promotes redistribution of energy in a wide range of organ systems, including the brain. Prolonged or cumulative increases in glucocorticoid secretion can reduce benefits afforded by enhanced stress reactivity and eventually become maladaptive. The long-term impact of stress is kept in check by the process of habituation, which reduces HPA axis responses upon repeated exposure to homotypic stressors and likely limits deleterious actions of prolonged glucocorticoid secretion. Habituation is regulated by limbic stress-regulatory sites, and is at least in part glucocorticoid feedback-dependent. Chronic stress also sensitizes reactivity to new stimuli. While sensitization may be important in maintaining response flexibility in response to new threats, it may also add to the cumulative impact of glucocorticoids on the brain and body. Finally, unpredictable or severe stress exposure may cause long-term and lasting dysregulation of the HPA axis, likely due to altered limbic control of stress effector pathways. Stress-related disorders, such as depression and PTSD, are accompanied by glucocorticoid imbalances and structural/ functional alterations in limbic circuits that resemble those seen following chronic stress, suggesting that inappropriate processing of stressful information may be part of the pathological process.

Influence of hypothalamic IL-6/gp130 receptor signaling on the HPA axis response to chronic stress

Abnormal basal activity and stress-evoked reactivity of the hypothalamic-pituitary-adrenal (HPA) axis are often seen in depression, implicating HPA axis dysfunction as a potentially causative or exacerbating factor. Chronic stress is also a factor in depression, but it is not known what may underlie the shift from adaptive to maladaptive HPA activity over the course of chronic stress. Interleukin 6 (IL-6), a stress-inducible cytokine that signals through gp130 and IL-6Rα receptors to activate the JAK/STAT3 signaling cascade, is elevated in some subtypes of depression, and may have a modulatory effect on HPA activation, raising the possibility that IL-6 contributes to depression through effects on the HPA axis. In this study, we examined the effects of three different stress modalities, acute footshock, chronic intermittent cold (CIC) stress and chronic unpredictable stress (CUS) on IL-6 signaling in the hypothalamus. We also investigated whether IL-6 modulates the HPA response to chronic stress, by blocking IL-6 signaling in the brain during CIC stress using either a neutralizing antibody or an inhibitor of STAT3 phosphorylation. We show that IL-6 and STAT3 in the hypothalamus are activated in response to footshock and CUS. We also found that basal IL-6 signaling through the JAK/STAT3 pathway is required for the sustained CORT response to chronic, but not acute, cold stress and therefore is a potential determinant of plasticity in the HPA axis specifically during chronic stress exposure.

Temporal association of elevated cholecystokininergic tone and adolescent trauma is critical for posttraumatic stress disorder-like behavior in adult mice

Adolescent trauma (AT) is a common risk factor for adult-onset posttraumatic stress disorder (PTSD). However, the vulnerability to AT among different individuals varies dramatically, indicating that other cofactors are important. Despite extensive studies, the identification of those cofactors has had little success. Here, we found that after subjected to traumatic stress at postnatal day 25 (P25), a stage that is comparable to the human adolescent period, inducible/reversible forebrain-specific cholecystokinin receptor-2 transgenic (IF-CCKR-2 tg) mice exhibited a significantly higher level of PTSD-like behavior at a later life (adult) stage compared with their wild-type littermates. Moreover, in these traumatized IF-CCKR-2 tg mice, both the glucocorticoid negative feedback inhibition and spatial learning and memory were impaired. Interestingly, if the CCKR-2 transgene was specifically suppressed during the time of AT exposure, these observations were largely diminished, indicating that a temporal association of the elevated CCKergic tone and AT is pathogenically critical. Treatment of traumatized IF-CCKR-2 tg mice with fluoxetine, a selective serotonin reuptake inhibitor, for a period of 4 wk significantly attenuated the PTSD-like behavior and the impaired glucocorticoid negative feedback inhibition, but not the memory deficit, implying that the memory deficit is an independent post-AT clinical entity and not a consequence of PTSD. Taken together, these results reveal a dynamic role of the CCKergic system in the development of post-AT psychopathologies and suggest that a timely antagonism of CCKR-2 activity during AT exposure is a potential preventive strategy for post-AT psychopathologies including PTSD and cognitive dysfunction.

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.

Acupuncture stimulation and neuroendocrine regulation

Acupuncture has been used to treat different conditions for at least 3000 years in China and has gained increasing acceptance worldwide. The acupuncture needle inserted into the muscle layer at the acupoint produces the so-called obtaining qi sensation that causes the excitation of A-δ and C-fibers of the muscle tissue, resulting in afferent signals. The afferent signals pass through the dorsal horn cells of the spinal cord ascending to the brain, such as the hypothalamus, enhancing the release of neuropeptides and hormones, and these afferent signals in the spinal segment may innervate the visceral organ, inducing effect on visceral function. Here, we reviewed the effect of acupuncture stimulation on neuropeptides and hormones, including β-endorphin, serotonin, oxytocin, adrenocorticotropic hormone, gonadotropin-releasing hormone, corticotrophin-releasing hormone, cholecystokinin, and acetylcholine, as well as insulin sensitivity, immunomodulation (anti-inflammation), and autonomic nerve activity.

Repeated stressor exposure regionally enhances beta-adrenergic receptor-mediated brain IL-1β production

It has been proposed that increased brain cytokines during repeated stressor exposure can contribute to neuropathological changes that lead to the onset of depression. Previous studies demonstrate that norepinephrine acting via beta-adrenergic receptors (β-ARs) mediate brain IL-1 production during acute stressor exposure. The aim of the current studies was to examine how the regulation of brain cytokines by adrenergic signaling might change following repeated stressor exposure. Fischer rats were exposed to four days of chronic mild stress and 24h after the last stressors β-AR expression, norepinephrine turnover, and β-AR-mediated induction of brain IL-1 were measured in limbic areas (e.g. hypothalamus, hippocampus, amygdala, and prefrontal cortex) and brainstem. Repeated stressor exposure resulted in decreases in β-AR expression (B(max)) measured by saturation binding curves in many limbic brain areas, while an increase was observed in the brainstem. This coincided with significant increases in norepinephrine turnover in the prefrontal cortex, hypothalamus, and amygdala, a significant increase in norepinephrine turnover was not observed in the hippocampus or brainstem. Stress increased overall IL-1 production in the amygdala (both basal and stimulated). While stress did not affect basal IL-1 levels in any other brain area, central administration of isoproterenol (a β-AR agonist) augmented IL-1 production in the hypothalamus of stressed animals. These data indicate that repeated stressor exposure results in brain area specific enhancements in β-AR-mediated IL-1 production and extends current knowledge of stress-induced enhancement of brain cytokine beyond sensitized response to immunological stimuli.

Relationship between Toe Temperature and Lower Urinary Tract Symptoms

OBJECTIVE

Cold stress can elicit increases in urinary urgency and frequency. We determined if there was a relationship between finger and toe temperatures and lower urinary tract symptoms (LUTS).

METHODS

We studied 50 people who visited a public health management seminar. The participants were divided into two groups according to self-described sensitivity to cold stress. The cold non-sensitive (CNS) group consisted of 3 males and 20 females (66.9 ± 10.8 years old), and the cold sensitive (CS) group consisted of 4 males and 23 females (65.8 ± 8.01 years old). Each participant was assessed to determine international prostate symptom score (IPSS), overactive bladder symptom score (OABSS), and quality of life (QOL) score. They were then instructed on lifestyle changes and exercises that could improve peripheral blood flow and provide relief for their LUTS. Next, the temperatures of their middle fingers and toes were measured before and after 5-10 min of the exercises. Two weeks later, the IPSS, OABSS, and QOL scores were reassessed.

RESULTS

Before exercise, the middle fingers were significantly warmer than the middle toes. Exercise had no significant effect on the middle finger temperature of either group; however, it did increase the middle toe temperature for both groups. The increase was greatest for the CS group. The CS group had higher LUTS storage symptoms than the CNS group, and these improved after 2 weeks of lifestyle changes and exercise.

CONCLUSION

Improvements in lifestyle and daily exercise may be effective for LUTS in CS people.

Effects of chronic plus acute prolonged stress on measures of coping style, anxiety, and evoked HPA-axis reactivity

Exposure to psychological trauma is the precipitating factor for PTSD. In addition, a history of chronic or traumatic stress exposure is a predisposing risk factor. We have developed a Chronic plus Acute Prolonged Stress (CAPS) treatment for rats that models some of the characteristics of stressful events that can lead to PTSD in humans. We have previously shown that CAPS enhances acute fear responses and impairs extinction of conditioned fear. Further, CAPS reduced the expression of glucocorticoid receptors in the medial prefrontal cortex. In this study we examined the effects of CAPS exposure on behavioral stress coping style, anxiety-like behaviors, and acute stress reactivity of the hypothalamic-pituitary-adrenal (HPA) axis. Male Sprague-Dawley rats were exposed to CAPS treatment, consisting of chronic intermittent cold stress (4 °C, 6 h/day, 14 days) followed on day 15 by a single 1-h session of sequential acute stressors (social defeat, immobilization, swim). After CAPS or control treatment, different groups were tested for shock probe defensive burying, novelty suppressed feeding, or evoked activation of adrenocorticotropic hormone (ACTH) and corticosterone release by an acute immobilization stress. CAPS resulted in a decrease in active burying behavior and an increase in immobility in the shock probe test. Further, CAPS-treated rats displayed increases in the latency to feed in the novelty suppressed feeding test, despite an increase in food intake in the home cage. CAPS treatment also reduced the HPA response to a subsequent acute immobilization stress. These results further validate CAPS treatment as a rat model of relevance to PTSD, and together with results reported previously, suggest that CAPS impairs fear extinction, shifts coping behavior from an active to a more passive strategy, increases anxiety, and alters HPA reactivity, resembling many aspects of human PTSD.

Nicotine modulates multiple regions in the limbic stress network regulating activation of hypophysiotrophic neurons in hypothalamic paraventricular nucleus

Nicotine intake affects CNS responses to stressors. We reported that nicotine self-administration (SA) augmented the hypothalamo-pituitary-adrenal (HPA) stress response, in part because of the altered neurotransmission and neuropeptide expression within hypothalamic paraventricular nucleus (PVN). Limbic-PVN interactions involving medial prefrontal cortex, amygdala, and bed nucleus of the stria terminalis (BST) greatly impact the HPA stress response. Therefore, we investigated the effects of nicotine SA on stress-induced neuronal activation in limbic-PVN network, using c-Fos protein immunohistochemistry and retrograde tracing. Nicotine decreased stress-induced c-Fos in prelimbic cortex (PrL), anteroventral BST (avBST), and peri-PVN, but increased c-Fos induction in medial amygdala (MeA), locus coeruleus, and PVN. Fluoro-gold (FG) was injected into avBST or PVN, as GABAergic neurons in avBST projecting to PVN corticotrophin-releasing factor neurons relay information from both PrL glutamatergic and MeA GABAergic neurons. The stress-induced c-Fos expression in retrograde-labeled FG+ neurons was decreased in PrL by nicotine, but increased in MeA, and also reduced in avBST. Therefore, within limbic-PVN network, nicotine SA exerts selective regional effects on neuronal activation by stress. These findings expand the mechanistic framework by demonstrating altered limbic-BST-PVN interactions underlying the disinhibition of PVN corticotrophin-releasing factor neurons, an essential component of the amplified HPA response to stress by nicotine.

Synaptic regulation of the hypothalamic-pituitary-adrenal axis and its modulation by glucocorticoids and stress

Dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis has been implicated in a range of affective and stress-related disorders. The regulatory systems that control HPA activity are subject to modulation by environmental influences, and stressful life events or circumstances can promote subsequent HPA dysregulation. The brain is a major regulator of the HPA axis, and stress-induced plasticity of the neural circuitry involved in HPA regulation might constitute an etiological link between stress and the development of HPA dysregulation. This review focuses on the synaptic regulation of neuroendocrine corticotropin-releasing hormone (CRH) neurons of the hypothalamic paraventricular nucleus, which are the cells through which the brain predominantly exerts its influence on the HPA axis. CRH neuronal activity is largely orchestrated by three neurotransmitters: GABA, glutamate, and norepinephrine. We discuss our current understanding of the neural circuitry through which these neurotransmitters regulate CRH cell activity, as well as the plastic changes in this circuitry induced by acute and chronic stress and the resultant changes in HPA function.

Synaptic regulation of the hypothalamic-pituitary-adrenal axis and its modulation by glucocorticoids and stress

Dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis has been implicated in a range of affective and stress-related disorders. The regulatory systems that control HPA activity are subject to modulation by environmental influences, and stressful life events or circumstances can promote subsequent HPA dysregulation. The brain is a major regulator of the HPA axis, and stress-induced plasticity of the neural circuitry involved in HPA regulation might constitute an etiological link between stress and the development of HPA dysregulation. This review focuses on the synaptic regulation of neuroendocrine corticotropin-releasing hormone (CRH) neurons of the hypothalamic paraventricular nucleus, which are the cells through which the brain predominantly exerts its influence on the HPA axis. CRH neuronal activity is largely orchestrated by three neurotransmitters: GABA, glutamate, and norepinephrine. We discuss our current understanding of the neural circuitry through which these neurotransmitters regulate CRH cell activity, as well as the plastic changes in this circuitry induced by acute and chronic stress and the resultant changes in HPA function.

Different stressors produce excitation or inhibition of mesolimbic dopamine neuron activity: response alteration by stress pre-exposure

Stressors can exert a wide variety of responses, ranging from adaptive responses to pathological changes; moreover, recent studies suggest that mild stressors can attenuate the response of a system to major stressful events. We have previously shown that 2-week exposure to cold, a comparatively mild inescapable stressor, induced a pronounced reduction in ventral tegmental area (VTA) dopamine (DA) neuron activity, whereas restraint stress increases DA neuron activity. However, it is not known if these stressors differentially impact the VTA in a region-specific manner, if they differentially impact behavioral responses, or whether the effects of such different stressors are additive or antagonistic with regard to their impact on DA neuron firing. To address these questions, single-unit extracellular recordings were performed in anesthetized control rats and rats exposed to chronic cold, and tested after delivery of a 2-h restraint session. Chronic cold stress strongly attenuated the number of DA neurons firing in the VTA, and this effect occurred primarily in the medial and central VTA regions that preferentially project to reward-related ventral striatal regions. Chronic cold exposure also prevented the pronounced increase in DA neuron population activity without affecting the behavioral sensitization to amphetamine produced by restraint stress. Taken together, these data show that a prolonged inescapable mild stressor can induce plastic changes that attenuate the DA system response to acute stress.

Cold Stress and Urinary Frequency

There have been few studies regarding the onset of urinary sensations and frequent urination induced by sudden whole-body cooling. In this article, we review the relationship between cold stress and urinary frequency based mainly on our previous studies. A recent study showed that cold stress induces bladder overactivity in conscious rats, and these effects were mediated, at least in part, by α1A -adrenergic receptor (AR) and α1D -AR. Another study suggested that the resiniferatoxin-sensitive nerves present in the urinary bladder may also be involved in the regulation of detrusor activity associated with cold stress. The mammalian transient receptor potential (TRP) channel family consists of 28 channels subdivided into five different classes: TRPV (vanilloid), TRPC (canonical), TRPM (melastatin), TRPML (mucolipin), and TRPA (ankyrin). TRP channels function as multifunctional sensors at the cellular level. They can be activated by physical (voltage, heat, cold, mechanical stress) or chemical stimuli and binding of specific ligands. In 2002, it was reported that a nonselective cation channel, TRPM8, could be activated by both menthol and thermal stimuli (8-28 °C). We demonstrated the presence of TRPM8 in the skin from the legs and back of rats by immunofluorescence staining and that stimulation of this receptor by menthol causes urinary frequency. There have been other reports demonstrating roles of TRPM8 not related to its thermosensory function. Further studies are needed to clarify the mechanism of cold stress-induced urinary frequency, and the roles of TRPM8 in the micturition control system.

Roles of the locus coeruleus and adrenergic receptors in brain-mediated hypothalamic-pituitary-adrenal axis responses to intracerebroventricular alcohol

BACKGROUND

Alcohol activates the hypothalamic-pituitary-adrenal (HPA) axis through its actions in both the periphery and the central nervous system (CNS). The studies presented here were designed to test the CNS-specific noradrenergic mechanisms by which alcohol stimulates HPA activity in the male rat.

METHODS

We used an experimental paradigm in which a small, nontoxic amount (5 μl) of alcohol was slowly microinfused intracerebroventricularly (icv). Alcohol was administered icv to animals with lesions of the locus coeruleus (LC) or in animals pretreated with α- or β-adrenergic receptor antagonists. Hormonal HPA activation was determined by measuring secretion of the pituitary stress hormone adrenocorticotropin (ACTH). Neuronal activation was determined by quantification of the expression of the transcription factor c-fos (Fos).

RESULTS

As expected, icv alcohol stimulated ACTH secretion from the pituitary and Fos expression in the paraventricular nucleus of the hypothalamus (PVN). Bilateral electrolytic LC lesions blocked the ability of icv alcohol to stimulate ACTH secretion. Pretreatment with icv propranolol increased basal ACTH secretion levels, but icv alcohol did not increase this effect. Propranolol also blunted icv alcohol-induced PVN Fos expression. A low dose of phenoxybenzamine, an α-adrenergic receptor antagonist, did not affect the ability of icv alcohol to stimulate ACTH release. However, a higher dose of the drug was able to block the ACTH response to icv alcohol. Despite this, phenoxybenzamine did not inhibit alcohol-induced Fos expression. Icv pretreatment with corynanthine, a selective α-1 adrenergic receptor antagonist, modestly raised basal ACTH levels and blocked the icv alcohol-induced secretion of this hormone.

CONCLUSIONS

These results indicate that the LC and norepinephrine play important roles in HPA activation caused by icv alcohol administration, but that the specific adrenergic receptor subtypes involved in this phenomenon still need to be identified.

Chronic intermittent cold stress sensitizes neuro-immune reactivity in the rat brain

Chronic stress contributes to many neuropsychiatric disorders in which the HPA axis, cognition and neuro-immune activity are dysregulated. Patients with major depression, or healthy individuals subjected to acute stress, present elevated levels of circulating pro-inflammatory markers. Acute stress also activates pro-inflammatory signals in the periphery and in the brain of rodents. However, despite the clear relevance of chronic stress to human psychopathology, the effects of prolonged stress exposure on central immune activity and reactivity have not been well characterized. Our laboratory has previously shown that, in rats, chronic intermittent cold stress (CIC stress, 4°C, 6h/day, 14 days) sensitizes the HPA response to a subsequent novel stressor, and produces deficits in a test of cognitive flexibility that is dependent upon prefrontal cortical function. We have hypothesized that CIC stress could potentially exert some of these effects by altering the neuro-immune status of the brain, leading to neuronal dysfunction. In this study, we have begun to address this question by determining whether previous exposure to CIC stress could alter the subsequent neuro-immune response to an acute immunological challenge (lipopolysaccharide, LPS) or an acute heterologous stressor (footshock). We examined the response of the pro-inflammatory cytokines, IL1β and IL6, the enzyme cyclooxygenase 2, and the chemokines, CXCL1 and MCP-1 in plasma, hypothalamus and prefrontal cortex. There was no effect of CIC stress on basal expression of these markers 24h after the termination of stress. However, CIC stress enhanced the acute induction of the pro-inflammatory cytokines, IL1β and particularly IL6, and the chemokines, CXCL1 and MCP-1, in plasma, hypothalamus and prefrontal cortex in response to LPS, and also sensitized the hypothalamic IL1β response to acute footshock. Thus, sensitization of acute pro-inflammatory responses in the brain could potentially mediate some of the CIC-dependent changes in HPA and cognitive function.

Prenatal stress induces long term stress vulnerability, compromising stress response systems in the brain and impairing extinction of conditioned fear after adult stress

Stress is a risk factor for the development of affective disorders, including depression, post-traumatic stress disorder, and other anxiety disorders. However, not all individuals who experience either chronic stress or traumatic acute stress develop such disorders. Thus, other factors must confer a vulnerability to stress, and exposure to early-life stress may be one such factor. In this study we examined prenatal stress (PNS) as a potential vulnerability factor that may produce stable changes in central stress response systems and susceptibility to develop fear- and anxiety-like behaviors after adult stress exposure. Pregnant Sprague-Dawley rats were immobilized for 1 h daily during the last week of pregnancy. Controls were unstressed. The male offspring were then studied as adults. As adults, PNS or control rats were first tested for shock-probe defensive burying behavior, then half from each group were exposed to a combined chronic plus acute prolonged stress (CAPS) treatment, consisting of chronic intermittent cold stress (4 °C, 6 h/d, 14 days) followed on day 15 by a single session of sequential acute stressors (social defeat, immobilization, cold swim). After CAPS or control treatment, different groups were tested for open field exploration, social interaction, or cued fear conditioning and extinction. Rats were sacrificed at least 5 days after behavioral testing for measurement of tyrosine hydroxylase (TH) and glucocorticoid receptor (GR) expression in specific brain regions, and plasma adrenocorticotropic hormone (ACTH) and corticosterone. Shock-probe burying, open field exploration and social interaction were unaffected by any treatment. However, PNS elevated basal corticosterone, decreased GR protein levels in hippocampus and prefrontal cortex, and decreased TH mRNA expression in noradrenergic neurons in the dorsal pons. Further, rats exposed to PNS plus CAPS showed attenuated extinction of cue-conditioned fear. These results suggest that PNS induces vulnerability to subsequent adult stress, resulting in an enhanced fear-like behavioral profile, and dysregulation of brain noradrenergic and hypothalamic-pituitary-adrenal axis (HPA) activity.

Bi-directional effect of cholecystokinin receptor-2 overexpression on stress-triggered fear memory and anxiety in the mouse

Fear, an emotional response of animals to environmental stress/threats, plays an important role in initiating and driving adaptive response, by which the homeostasis in the body is maintained. Overwhelming/uncontrollable fear, however, represents a core symptom of anxiety disorders, and may disturb the homeostasis. Because to recall or imagine certain cue(s) of stress/threats is a compulsory inducer for the expression of anxiety, it is generally believed that the pathogenesis of anxiety is associated with higher attention (acquisition) selectively to stress or mal-enhanced fear memory, despite that the actual relationship between fear memory and anxiety is not yet really established. In this study, inducible forebrain-specific cholecystokinin receptor-2 transgenic (IF-CCKR-2 tg) mice, different stress paradigms, batteries of behavioral tests, and biochemical assays were used to evaluate how different CCKergic activities drive fear behavior and hormonal reaction in response to stresses with different intensities. We found that in IF-CCKR-2 tg mice, contextual fear was impaired following 1 trial of footshock, while overall fear behavior was enhanced following 36 trials of footshock, compared to their littermate controls. In contrast to a standard Yerkes-Dodson (inverted-U shaped) stress-fear relationship in control mice, a linearized stress-fear curve was observed in CCKR-2 tg mice following gradient stresses. Moreover, compared to 1 trial, 36 trials of footshock in these transgenic mice enhanced anxiety-like behavior in other behavioral tests, impaired spatial and recognition memories, and prolonged the activation of adrenocorticotropic hormone (ACTH) and glucocorticoids (CORT) following new acute stress. Taken together, these results indicate that stress may trigger two distinctive neurobehavioral systems, depending on both of the intensity of stress and the CCKergic tone in the brain. A “threshold theory” for this two-behavior system has been suggested.