Non-selective orexin-receptor antagonist attenuates stress-re-stress-induced core PTSD-like symptoms in rats: Behavioural and neurochemical analyses.

Post-traumatic stress disorder (PTSD) is a psychological disorder affecting many around the world. Growing evidence suggests that orexin-A is involved in the pathophysiology of depression and panic anxiety disorder. However, the role of orexin-A in PTSD remains unclear. Therefore, pharmacological manipulation of orexin-A can be a potential approach for the treatment of PTSD. Male Wistar rats were subjected to stress re-stress (SRS) by restraining them for 2 h followed by foot shock (FS) and halothane exposure on day-2 (D-2). Then the rats were weekly exposed to FS as re-stress cue . Suvorexant, an orexin antagonist (10, 20 and 30 mg/kg p.o.) and paroxetine (10 mg/kg p.o.) were administered from D-8 to D-32. Plasma and cerebrospinal fluid (CSF) were collected for corticosterone and orexin-A measurement. The analysis of serotonin and corticotropin-releasing factor receptor-1 (CRF-R1) were performed in the amygdalar tissue. SRS-induced PTSD-like symptoms like fear response, anxiety-like behaviour and hypocorticosteronism were attenuated by suvorexant and paroxetine. Interestingly, SRS exposed rats showed activation of orexin-A and serotonergic systems, which were also attenuated by suvorexant. Additionally, suvorexant ameliorated the extrahypothalamic induced upregulation of CRH-R1 in SRS-exposed rats. Therefore, orexin-A may be considered as a neurochemical-marker for PTSD and suvorexant alleviated PTSD-like symptoms through modulating orexinergic, serotonergic and neuroendocrine systems.

Short-term sleep fragmentation enhances anxiety-related behavior: The role of hormonal alterations.

INTRODUCTION: The neuroendocrine background of acute sleep fragmentation in obstructive sleep apnea and sleep fragmentation involvement in psychiatric comorbidities, common in these patients, are still largely unknown. The aim of this study was to determine the effects of short-term experimental sleep fragmentation on anxiety -like behavior and hormonal status in rats. METHODS: Male rats were adapted to treadmill (ON and OFF mode with belt speed set on 0.02m/s and 0.00m/s) and randomized to: 1) treadmill control (TC, only OFF mode); 2) motion, activity control (AC, 10min ON and 30min OFF mode) and 3) sleep fragmentation (SF, 30s ON and 90s OFF mode) group. Six hours later, the animals were tested in the open field, elevated plus maze and light/dark test (n = 8/group). Testosterone, estradiol, progesterone and corticosterone were determined in separate animal cohort immediately upon sleep fragmentation (n = 6/group). RESULTS: SF rats showed decreased rearings number, decreased time spent in the central area and increased thigmotaxic index compared to TC and AC rats in the open field test. Similarly, increased anxiety upon sleep fragmentation was observed in the elevated plus maze and the light/dark test. Significantly lower testosterone, estradiol and progesterone levels were determined in SF in comparison to AC and TC groups, while there was no significant difference in the levels of corticosterone. CONCLUSION: Short term sleep fragmentation enhances anxiety-related behavior in rats, which could be partly mediated by the observed hormonal changes presented in the current study in form of testosterone, estradiol and progesterone depletion.

Markers of HPA-axis activity and nucleic acid damage from oxidation after electroconvulsive stimulations in rats.

OBJECTIVE: Oxidative stress has been suggested to increase after electroconvulsive therapy (ECT), a treatment which continues to be the most effective for severe depression. Oxidative stress could potentially be mechanistically involved in both the therapeutic effects and side effects of ECT. METHODS: We measured sensitive markers of systemic and central nervous system (CNS) oxidative stress on DNA and RNA (urinary 8-oxodG/8-oxoGuo, cerebrospinal fluid 8-oxoGuo, and brain oxoguanine glycosylase mRNA expression) in male rats subjected to electroconvulsive stimulations (ECS), an animal model of ECT. Due to the previous observations that link hypothalamic-pituitary-adrenal (HPA)-axis activity and age to DNA/RNA damage from oxidation, groups of young and middle-aged male animals were included, and markers of HPA-axis activity were measured. RESULTS: ECS induced weight loss, increased corticosterone (only in middle-aged animals), and decreased cerebral glucocorticoid receptor mRNA expression, while largely leaving the markers of systemic and CNS DNA/RNA damage from oxidation unaltered. CONCLUSION: These results suggest that ECS is not associated with any lasting effects on oxidative stress on nucleic acids neither in young nor middle-aged rats.

Monoamines, BDNF, IL-6 and corticosterone in CSF in patients with Parkinson's disease and major depression.

The biochemical basis of major depression (MD) in Parkinson's disease (PD) is largely unknown. To increase our understanding of MD in PD patients, the levels of monoamine metabolites (HVA, 5-HIAA and MHPG), BDNF, orexin-A, IL-6 and corticosterone were examined in cerebrospinal fluid. The analyses were performed in MD patients with (n = 11) and without (n = 12) PD at baseline and after 12 weeks' of treatment with the antidepressant citalopram, and in patients with solely PD (n = 14) at baseline and after 12 weeks. The major findings were that PD patients with MD had significantly lower baseline levels of MHPG, corticosterone and IL-6 when compared to patients with solely MD. In response to citalopram treatment, patients with solely MD exhibited an expected decrease in 5-HIAA and MHPG levels which was not found in PD patients with MD. Moreover, the levels of BDNF and IL-6 were lower in PD patients with MD compared with patients with solely MD after treatment with citalopram. Thus, the biochemical basis and the response to citalopram differ between PD patients with MD and patients with solely MD.

Antidepressant-like effects of psoralen isolated from the seeds of Psoralea corylifolia in the mouse forced swimming test.

The forced swimming test (FST) is suggested to produce abnormalities in the serotonergic and hypothalamic-pituitary-adrenal (HPA) axis systems. Therefore, compounds that attenuate these neurobiological alterations may have potential as antidepressants. The behavioral and biochemical effects of psoralen, a major furocoumarin isolated from Psoralea corylifolia, were investigated in the FST model of depression in male mice. Psoralen significantly reduced immobility and increased swimming without altering climbing in the mouse FST. Psoralen remarkably reversed FST-induced alterations in serotonin (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) levels in frontal cortex and hippocampus in mice. Furthermore, psoralen attenuated FST-induced elevations in serum corticotropin-releasing factor (CRF) and corticosterone concentrations to normalize the HPA axis activity. These results suggested that psoralen possessed potent antidepressant-like properties which were at least in part mediated by improving the abnormalities in the serotonergic and the HPA axis systems.

Selective blockade of the rat brain aqueduct with thermogelling hydrogel nanoparticle dispersion.

Experimental methods targeting molecules or drugs to specific neuronal tissue(s) can be important in determining function. In this study we focused on blockade of the small channel or aqueduct connecting the third and fourth ventricles of the rat brain. A cannula was placed into the aqueduct between the third and fourth ventricle. A second cannula was placed into the third or fourth ventricle. An aqueous dispersion of hydrogel nanoparticles, that maintains a liquid state at temperatures below 33 degrees C and solidifies near body temperature (35 degrees C), was infused into the aqueduct. Two interpenetrating polymer networks (IPN) of hydrogel nanoparticles with polymer concentrations at 2% by weight and 3% by weight were separately infused into the aqueduct to block cerebrospinal fluid (CSF) flow. Following infusion of hydrogel CSF was isolated to a particular ventricle as shown by the lack of dye movement between the ventricles. In addition, stress hormone, corticosterone, feeding behavior and blood glucose levels were measured. Results show upon reaching the aqueduct the hydrogel dispersion solidified and restricted the flow of CSF. A higher concentration of dispersion (3% wt.) was more effective in blocking the aqueduct and isolating the third from the fourth ventricle. Over the period of measurement, infusion of the dispersion had no measurable detrimental physiological effects on the animal. We conclude that isolation of ventricles in the brain can be completed for 48-h by using dispersions of hydrogel nanoparticles and the effects of drugs on certain brain tissues can be determined with this method.

The role of corticosterone in human hypothalamic-pituitary-adrenal axis feedback.

OBJECTIVE: In humans, the glucocorticoid corticosterone circulates in blood at 10-20-fold lower levels than cortisol, but is found in higher relative amounts in postmortem brain samples. Access of cortisol and corticosterone to the central nervous system may not be equal. Additionally, the relative affinities for the glucocorticoid and mineralocorticoid receptors differ, such that corticosterone may play a significant role in human brain function. DESIGN: We measured cortisol and corticosterone levels in paired plasma and cerebrospinal fluid (CSF) samples. To test the relative potency of cortisol vs. corticosterone on hypothalamic-pituitary-adrenal (HPA) feedback, subjects underwent a three-phase, single-blind, randomized study assessing the postmetyrapone ACTH response over 3 h to an intravenous bolus of vehicle, cortisol or corticosterone (0.15 mg/kg and 0.04 mg/kg). PARTICIPANTS: Outpatients undergoing diagnostic lumbar puncture who were subsequently deemed to be free of disease. Feedback was tested in healthy male volunteers. MEASUREMENTS: Plasma and CSF corticosterone to cortisol ratio was calculated and the ACTH response over time after the bolus glucocorticoid measured. RESULTS: Plasma corticosterone : cortisol was 0.069 +/- 0.007; CSF corticosterone : cortisol was 0.387 +/- 0.050 (P < 0.001). Cortisol and corticosterone (0.15 mg/kg) suppressed ACTH vs. vehicle (P = 0.002); there was no difference between corticosterone and cortisol. The 0.04 mg/kg dose had no effect on ACTH despite supraphysiological plasma corticosterone levels. CONCLUSIONS: Corticosterone contributes almost 40% of total active glucocorticoids (cortisol and corticosterone) in the CSF. Significant effects on HPA axis suppression were only seen with supraphysiological levels of corticosterone, suggesting that corticosterone is not important in this model of nonstress-induced ACTH hypersecretion, in which the effect of cortisol predominates.

Experimentally-induced hyperthyroidism is associated with activation of the rat hypothalamic-pituitary-adrenal axis.

OBJECTIVE: Previous studies on the effects of altered thyroid function on the secretion and metabolism of adrenocortical hormones suggest a degree of adrenocortical hyperactivity in hyperthyroidism. We have previously shown that experimentally-induced hyperthyroidism is associated with significant alterations in pituitary-adrenal responsiveness to synthetic ovine corticotropin-releasing hormone (oCRH) that are contingent upon the duration of the altered thyroid function. The purpose of this study was to assess the time-dependent effects of hyperthyroidism on the functional integrity of the hypothalamic-pituitary-adrenal (HPA) axis by in vivo stimulation of the hypothalamic CRH neuron and adrenal cortex. METHODS: The functional integrity of the HPA axis was examined in vivo in sham-thyroidectomized male Sprague-Dawley rats given placebo or in thyroidectomized rats given 50 mug of thyroxine every day for 7 or 60 days. Responses to insulin-induced hypoglycemia and IL-1alpha stimulation were used to assess the hypothalamic CRH neuron. Adrenocortical reserve was assessed in response to low-dose adrenocorticotropic hormone (ACTH), following suppression of the HPA axis with dexamethasone. Adrenal and thymus tissue weight, in addition to basal plasma ACTH, corticosterone and thyroid indices were also determined. RESULTS: Basal plasma corticosterone and corticosterone binding globulin (CBG) concentrations were significantly increased in short- and long-term hyperthyroid rats, and by 60 days, cerebrospinal fluid (CSF) corticosterone levels were significantly increased. Basal plasma ACTH levels were similar to controls. Although plasma ACTH responses to hypoglycemic stress and IL-1alpha administration in both short- and long-term hyperthyroidism were normal, corticosterone responses to the ACTH release during the administration of these stimuli were significantly increased. The adrenal reserve was significantly elevated in short-term hyperthyroidsim. Long-term hyperthyroidism, however, was associated with a significant reduction in adrenocortical reserve. A significant increase in adrenal weights and a decrease in thymus weights were observed in both short- and long-term hyperthyroidism. CONCLUSIONS: The available data confirms that hyperthyroidism is associated with hypercorticosteronemia, although the locus that is principally affected still remains unclear. Despite the sustained hyperactivity of the HPA axis, long-term experimentally-induced hyperthyroidism is associated with diminished adrenal functional reserve. The alterations in HPA function in states of disturbed thyroid function were found to be somewhat more pronounced as the duration of thyroid dysfunction increased.

Long-term consequences of neonatal rearing on central corticotropin-releasing factor systems in adult male rat offspring.

In a series of studies on the long-term consequences of neonatal rearing, we compared hypothalamic and extrahypothalamic central corticotropin-releasing factor (CRF) systems in male rats reared under conditions of animal facility rearing, nonhandling (HMS0), handling with brief maternal separation for 15 min (HMS15), or handling with moderate maternal separation for 180 min (HMS180) daily from postnatal days 2-14. CRF-like immunoreactivity (CRFir) was elevated in lumbar cerebrospinal fluid of adult HMS180 and HMS0 rats relative to the other groups. In the paraventricular nucleus, central nucleus of the amygdala, bed nucleus of the stria terminalis, and locus coeruleus, CRFir and CRF mRNA levels were significantly elevated in HMS0 and HMS180 rats. Neonatal maternal separation was associated with regionally specific alterations in CRF receptor type 1 (CRF1) mRNA density in HMS180 rats. No rearing-associated differences in CRF2alpha binding were apparent in either the lateral septum or the ventromedial hypothalamus. These findings indicate that early rearing conditions can permanently alter the developmental set-point of central CRF systems, and potentially influence the expression of behavioral and endocrine responses to stress throughout life, thereby providing a possible neurobiological substrate for the relationship between early life events and increased vulnerability for hypothalamic-pituitary-adrenal axis and coping skill alterations and the frequency of mood disorders in patients with a history of such experiences.