Group housing of mice increases immobility and antidepressant sensitivity in the forced swim and tail suspension tests

The forced swim test and tail suspension test are often used in laboratory practice to identify compounds that possess antidepressant-like activity. This experiment was conducted to determine whether housing conditions per se influence the response of mice in these antidepressant screening procedures. Male NIH Swiss mice were housed individually or in groups (five per cage) for 8 weeks prior to testing. After 8 weeks, the animals were exposed to the forced swim and tail-suspension tests. Group housed mice displayed high levels of immobility in the forced swim and tail suspension tests. Desipramine injection 60 min prior testing, in doses 7.5 and 15 mg/kg, produced significant reductions in the immobility time in forced swimming and tail suspension tests. Individually housed mice, when exposed to these tests, displayed lower levels of immobility with a magnitude comparable to the effect of desipramine in group housed mice. Desipramine given to individually housed mice did not reduce the duration of immobility either in the forced swim test or in the tail suspension test. These results indicate that both tests are sensitive to housing conditions. This observation suggests that long lasting group housing may be critical to the behavioral response in these preclinical screening procedures in mice.

Corticotropin-releasing factor receptor type 1 mediates stress-induced relapse to cocaine-conditioned place preference in rats

Corticotropin-releasing factor (CRF) has been suggested to play an important role in the development of drug dependence and withdrawal. Based on the recent finding that CRF receptor antagonists inhibit the stress-induced relapse to opiate dependence and attenuate anxiety-like responses related to cocaine withdrawal, the present experiment was performed to examine the possible effect of different CRF receptor antagonists on reactivation of cocaine-conditioned place preference induced by cocaine and stress in rats. The results show that a single injection of cocaine (10 mg/kg, i.p.) could reactivate cocaine-conditioned place preference following a 28-day extinction, and pretreatment with i.c.v. 10 microg alpha-helical CRF, a nonspecific CRF receptor antagonist, significantly attenuated this reactivation of conditioned place preference. However, pretreatment with i.p. 1 or 10 mg/kg CP-154,526 (butyl-[2,5-dimethyl-7-(2,4,6-trimethylphenyl)-7H-pyrrolo[2,3-d]pyrimidin-4-yl]-ethylamine), a specific CRF receptor subtype 1 antagonist, and i.c.v. 1 or 10 microg AS-30 ([D-Phe(11),His(12)]Svg-(11-40)), a specific CRF receptor subtype 2 antagonist, failed to show the same effects. In addition, a single footshock stress also elicited the reactivation of cocaine-conditioned place preference following a 28-day extinction and pretreatment with alpha-helical CRF (10 microg, i.c.v.) and CP-154,526 (1 or 10 mg/kg, i.p.) significantly blocked this effect. In contrast, pretreatment with AS-30 at a dose of 1 or 10 microg (i.c.v.) did not affect the stress-induced reactivation of cocaine-conditioned place preference. The present study demonstrated that CRF receptor type 1, but not CRF receptor type 2, mediates the stress-induced reactivation of cocaine-conditioned place preference. These findings suggest that CRF receptor subtype 1 antagonists might be of some value in the treatment and prevention of stress-induced relapse to drug dependence long after detoxification.

[Behavioral and neurochemical study on the mechanism of the anxiolytic effect of a selective serotonin reuptake inhibitor, a selective serotonin1A agonist and lithium carbonate]

The authors investigated the effects of citalopram [selective serotonin (5-HT) reuptake inhibitor; SSRI] and MKC-242 (a selective 5-HT1A agonist) following treatment with subchronic lithium (p.o., 1 week) on the expression of conditioned freezing, an index of anxiety, and on extracellular 5-HT concentrations in the medial prefrontal cortex (mPFC). In conditioned fear stress experiments, acute administration of citalopram (s.c.) reduced freezing significantly at a high dose (30 mg/kg), while showing no effect at lower doses (3 and 10 mg/kg). Acute administration of MKC-242 (s.c.; 0.1-10 mg/kg) dose-dependently reduced freezing. Subchronic lithium treatment (1 week; 0.05 or 0.2% lithium carbonate in diet; p.o.) showed no effect on freezing behavior. Acute treatment with both citalopram (3 and 30 mg/kg) and MKC-242 (1 mg/kg) after subchronic treatment with high, but not low, concentrations of lithium (1 week) reduced freezing markedly and significantly, as compared with either drug alone. In brain microdialysis experiments, acute treatment with citalopram showed significant increases in the extracellular 5-HT concentrations in a dose-dependent manner. Subchronic lithium group showed significantly higher basal levels of extracellular 5-HT, compared with normal diet controls. Acute citalopram (3 and 30 mg/kg) treatment with subchronic lithium treatment showed significant increases in the extracellular 5-HT concentrations, compared with citalopram treatment alone. Subchronic lithium did not cause decreases in extracellular 5-HT after presynaptic stimulation of 5-HT1A receptors by MKC-242. These results suggest that subchronic lithium treatment enhanced the anxiolytic-like effects of these serotonergic drugs by facilitating central 5-HT neurotransmission at clinically therapeutic plasma lithium levels. It is hypothesized that subchronic lithium treatment gives an additive effect to the treatment with citalopram (3 and 30 mg/kg) by increasing the extracellular 5-HT concentrations in the mPFC, and that subchronic lithium treatment enhances the anxiolytic effect of MKC-242 by increasing sensitivity of postsynaptic 5-HT1A receptors.

Regional wall stress predicts ventricular remodeling after anteroseptal myocardial infarction in the Healing and Early Afterload Reducing Trial (HEART): an echocardiography-based structural analysis

BACKGROUND

Increased left ventricular (LV) wall stress after myocardial infarction (MI) has been implicated in LV remodeling. However, the relationship between LV wall stress and LV remodeling is incompletely defined.

METHOD

We prospectively studied the relationship between regional wall stress and LV remodeling by application of the finite element method to end-systolic LV models from patients enrolled in the Healing and Early Afterload Reducing Therapy (HEART) Trial. Individual LV models were constructed from orthogonal apical echocardiographic views obtained at day 14 after anteroseptal MI in 64 patients. Of these, 31 patients received low-dose (0.625 mg) ramipril and 33 patients received full-dose (10 mg) ramipril. LV wall stress was calculated by the finite element method and correlated with change in LV volume from day 14 to day 90 after MI.

RESULTS

Among all patients, increases in apical regional wall stress were associated with LV volume changes (P -trend =.015). The relationship between apical regional wall stress and change in LV volume was strongest in the low-dose ramipril group (r = 0.53, P =.002) and remained significant after adjustment for end-diastolic volume, infarct size, ejection fraction, and systolic blood pressure yet was attenuated in the full-dose ramipril group.

CONCLUSIONS

Apical regional wall stress is an independent predictor of subsequent LV remodeling after MI. The relationship between increased apical wall stress and LV dilatation appears to be attenuated by full-dose angiotensin-converting enzyme inhibition.

Prenatal stress and postnatal development of neonatal rats--sex-dependent effects on emotional behavior and learning ability of neonatal rats

Maternal sound stress (800 Hz; 77 dB, every other minute for 15 min/day, from day 10 to 18 of gestation), combined with forced swimming stress (15 min/day), was found to cause potentiation of sound-induced loss of locomotor activity, referred to as emotional behavior, of male offspring, but not that of female offspring, at 4 weeks of age. Maternal stress also caused an increase in the total number of errors by male, but not female offspring in the water-maze test at 6 weeks of age. These effects of stress on emotional behavior and learning behavior were abolished when dams were pretreated with buspirone (30 min before the stress, from day 8 to 18 of gestation). Thus, prenatal stress might have sex-dependent effects on emotional behavior and learning ability of neonatal rats.

Development of differential tolerance to the sedative and anti-stress effects of benzodiazepines

Differential degree of tolerance has been reported to develop for anticonvulsant, sedative and skeletal muscle relaxant effects of benzodiazepines (BZDs). Acute treatment with BZDs reportedly reduces the formation of gastric stress ulcers and attenuates stress-induced immunosuppression. The present study investigates whether tolerance develops to these antistress effects of BZDs by using diazepam and chlordiazepoxide as representative drugs. A single dose of diazepam (5 mg/kg, i.p.) or chlordiazepoxide (20 mg/kg, i.p.) produced a significant reduction in locomotor activity, a measure of sedative effect and antagonized the effect of restraint stress (RS) on gastric mucosal lesions and anti-sheep red blood cell (SRBC) antibody titre. With chronic treatment (X 7 d), there was a marked tolerance to the sedative effect of both the studied BZD drugs, while much less tolerance developed to their ulcer protective action. However, no tolerance was observed to the attenuating effect of diazepam and chlordiazepoxide on RS-induced immunosuppression. Thus, the results of the present study indicate that different mechanisms may be involved in the development of tolerance to the sedative, antiulcer and immunomodulatory effects of BZDs.

Anti-oxidant effect of Withania somnifera glycowithanolides in chronic footshock stress-induced perturbations of oxidative free radical scavenging enzymes and lipid peroxidation in rat frontal cortex and striatum

The antioxidant activity of Withania somnifera (WS) glycowithanolides was assessed in chronic footshock stress induced changes in rat brain frontal cortex and striatum. The stress procedure, given once daily for 21 days, induced an increase in superoxide dismutase (SOD) and lipid peroxidation (LPO) activity, with concomitant decrease in catalase (CAT) and glutathione peroxidase (GPX) activities in both the brain regions. WS glycowithanolides (WSG), administered orally 1 h prior to the stress procedure for 21 days, in the doses of 10, 20 and 50 mg/kg, induced a dose-related reversal of the stress effects. Thus, WSG tended to normalise the augmented SOD and LPO activities and enhanced the activities of CAT and GPX. The results indicate that, at least part of chronic stress-induced pathology may be due to oxidative stress, which is mitigated by WSG, lending support to the clinical use of the plant as an antistress adaptogen.

Effect of Ocimum sanctum on noise induced changes in neutrophil functions

The effect of ethanolic extract of Ocimum sanctum was studied on the noise stress induced changes in albino rats. Acute noise stress caused leukopenia, increased corticosterone level and enhanced the neutrophil functions as indicated by an increase in the Candida phagocytosis and Nitro blue tetrazolium (NBT) reduction. Pretreatment with the O. sanctum Linn. (OS) extract brought back the stress altered values to normal levels indicating the stress alleviating effect of O. sanctum.

The sympathetic adrenomedullary system, but not the hypothalamic-pituitary-adrenal axis, participates in aorta adaptive response to stress: nitric oxide involvement

Stress induced a decrease in the reactivity of the aorta to noradrenaline (NA), as a consequence of an endothelial nitric oxide (NO) system hyperactivity. The main characteristic of the stress response is activation of the hypothalamic-pituitary-adrenal (HPA) axis and sympathetic adrenomedullary (SA) system. The participation of the HPA axis and SA system in the decreased reactivity to NA in the aorta of rats exposed to 4-h immobilization was investigated. Concentration-response relationships for NA were obtained in the aorta, with and without endothelium, isolated from normal and stressed rats, following these procedures: (1) in the absence and presence of L-NAME; (2) after adrenalectomy (ADX) or not, in the absence or presence of L-NAME; (3) ADX rats treated or not with corticosterone; (4) ADX associated with stress; and (5) treated or not with reserpine. The reactivity of aorta without endothelium was unaffected by the procedures. The reactivity of aorta with endothelium was decreased by either stress or ADX. This effect was reversed by both L-NAME and corticosterone. ADX did not potentiate the decrease in the aorta reactivity induced by stress. Reserpine did not change the reactivity of aorta with endothelium from normal rats, but prevented the decrease in reactivity induced by stress. It is concluded that the HPA axis participates in endothelium-dependent modulation of aorta reactivity in normal conditions and that the SA system participates in hyperactivity of the endothelial NO-system induced by stress, which is responsible for the decreased aorta reactivity to NA.

The anxiolytic effect of chronic inositol depends on the baseline level of anxiety

Inositol, a precursor for membrane phosphoinositides involved in signal transduction, has been found to be clinically effective in a number of psychiatric disorders and to reverse behavioural effects of lithium. To gain insight into the mechanism of action of inositol, it is critical to establish its efficacy in animal models. Following the initial report by Cohen et al. (1997b) that inositol was anxiolytic in the elevated plus maze model of anxiety, the effect of chronic intraperitoneal and chronic dietary inositol administration in rats was tested in four experiments. There was a significant increase in closed arm and total arm entries following chronic injection of inositol, but no effect of inositol when it was given chronically in rat chow. Because the first 2 experiments suggested that the mode of drug administration affected the control levels of anxiety (open arm entries and time in open arms) in control groups, the effect of chronic dietary inositol was tested in rats that were exposed to a mild and a more severe form of stress. Chronic saline injections elevated anxiety in the plus maze, which was only marginally affected by chronic dietary inositol. Following 3 weeks administration of 5% dietary inositol rats were pre-exposed to a cat. There was a clear increase in number of entries into open arms, suggesting an anxiolytic effect of inositol.

Long-term lithium administration abolishes the resistance to stress in rats sensitized to morphine

Morphine sensitized rats appear protected from the sequelae of an unavoidable stress: when exposed to stress (after a 7-day morphine wash-out) and then tested for escape, they perform like naive animals. This protection appears similar to that induced by chronic imipramine treatment, as it is antagonized by the inhibition of D(1)-dopamine receptors before exposure to unavoidable stress. Repeated unavoidable stress induces in rats a condition characterized by hyporeactivity to noxious stimuli and reverted by long-term antidepressant treatments, and this state is regarded as an experimental model of depression. The resistance to stress in morphine sensitized rats could be considered as the behavioral counterpart of the sensitivity to stress in control rats, i.e. as a model of mania. The aim of the present study was to validate such a putative model by studying whether the resistance to stress induced by morphine sensitization would respond to a long-term administration of lithium, the reference antimanic drug. Long-term lithium treatment induces in rats a condition of hyporeactivity to noxious stimuli, accompanied by decreased levels of dopamine in the nucleus accumbens shell. In morphine sensitized rats chronic lithium abolished the resistance to stress, but it did not modify the D(1)-dopamine receptor mediated response to morphine, nor did it modify the levels of extraneuronal dopamine in the nucleus accumbens shell. Thus, lithium treatment abolished the resistance to stress in morphine sensitized rats, conferring predictive validity to the paradigm. Moreover, it did so through a mechanism which appeared to be independent of D(1)-dopamine receptor activity.

Cocaine- and alcohol-mediated expression of inducible transcription factors is blocked by pentobarbital anesthesia

Identifying the neurocircuitry involved in behavioral responses to drugs of abuse is an important step towards understanding the mechanisms of drug addiction. The present study sought to distinguish brain regions involved in pharmacological effects of cocaine and ethanol from secondary effects by administering these drugs in the presence or absence of pentobarbital anesthesia. Changes in neuronal activity were assessed by immunohistochemical analysis of expression of an inducible transcription factor (ITF), c-Fos, in the brain of rats habituated to repeated pentobarbital anesthesia or saline administration. Cocaine administration (15 mg/kg, i.v.) in non-anesthetized animals produced a strong induction of c-Fos in the striatum and large number of other brain areas. Ethanol administration (2 g/kg, i.p.) induced c-Fos in a smaller number of characteristic brain areas, including the central nucleus of amygdala and paraventricular nucleus of hypothalamus. However, neither of these drugs was able to induce c-Fos in pentobarbital-anesthetized rats (50 mg/kg, i.v.). The suppressive effects of pentobarbital were not specific to c-Fos, such that pentobarbital also suppressed expression of ITFs FosB and Egr1 in the striatum of cocaine-treated rats. On the other hand, pentobarbital by itself strongly induced c-Fos expression in the lateral habenula of saline-, cocaine-, and ethanol-injected rats. It is not clear whether the suppressive effects of anesthesia on ITF expression in other areas are mediated by activation of lateral habenula, or are independent of this event. Our data suggest that in the absence of conscious awareness of drug-associated cues, cocaine and alcohol activate only a fraction of the neural elements engaged in the unanesthetized state.

Corticotropin-releasing factor receptor type I mediates stress-induced relapse to opiate dependence in rats

The possible effect of different corticotropin-releasing factor receptor (CRFR) antagonists (alpha-helical CRF, CP-154,526 and AS-30) on the maintenance and reactivation of morphine-conditioned place preference (CPP) induced by morphine or footshock stress, respectively, were investigated in rats. The results show that morphine-induced maintenance of CPP was not affected by pretreatment with any CRFR antagonists. However, morphine-induced the reactivation of CPP was significantly attenuated by pre-administration of 10 microg alpha-helical CRF (i.c.v.). The maintenance of morphine CPP could be induced by repeated footshock and this effect was significantly attenuated by pretreatment of 10 microg alpha-helical CRF (i.c.v.) and 10 mg CP-154,526 (i.p.). Furthermore, following a 28-day extinction of morphine CPP, a single footshock could again elicit the reactivation of place preference that was blocked by pretreatment with 10 microg alpha-helical CRF (i.c.v.) and 1 or 10 mg CP-154,526 (i.p.). The present study demonstrates that CRFR type 1, but not CRFR type 2, mediates the stress-induced maintenance and reactivation of morphine CPP. These findings suggest that CRFR type 1 antagonists might be of some value in the treatment and prevention of stress-induced relapse to drug dependence long after detoxification.

Scientific basis for the therapeutic use of Withania somnifera (ashwagandha): a review

OBJECTIVE

The objective of this paper is to review the literature regarding Withania somnifera (ashwagandha, WS) a commonly used herb in Ayurvedic medicine. Specifically, the literature was reviewed for articles pertaining to chemical properties, therapeutic benefits, and toxicity.

DESIGN

This review is in a narrative format and consists of all publications relevant to ashwagandha that were identified by the authors through a systematic search of major computerized medical databases; no statistical pooling of results or evaluation of the quality of the studies was performed due to the widely different methods employed by each study.

RESULTS

Studies indicate ashwagandha possesses anti-inflammatory, antitumor, antistress, antioxidant, immunomodulatory, hemopoietic, and rejuvenating properties. It also appears to exert a positive influence on the endocrine, cardiopulmonary, and central nervous systems. The mechanisms of action for these properties are not fully understood. Toxicity studies reveal that ashwagandha appears to be a safe compound.

CONCLUSION

Preliminary studies have found various constituents of ashwagandha exhibit a variety of therapeutic effects with little or no associated toxicity. These results are very encouraging and indicate this herb should be studied more extensively to confirm these results and reveal other potential therapeutic effects. Clinical trials using ashwagandha for a variety of conditions should also be conducted.

Chronic administration of the selective corticotropin-releasing factor 1 receptor antagonist CP-154,526: behavioral, endocrine and neurochemical effects in the rat

Corticotropin-releasing factor 1 (CRF(1)) receptor antagonists may represent a novel group of drugs for the pharmacotherapy of depression and/or anxiety disorders. We have investigated the behavioral, endocrine, and neurochemical effects of chronic administration of a selective CRF(1) receptor antagonist, CP-154,526. After 9 to 10 days of treatment with CP-154,526 (3.2 mg/kg/day), defensive withdrawal behavior was significantly decreased suggesting anxiolytic activity. In animals treated for 14 days with the low dose of CP-154,526, serum corticosterone concentrations returned to baseline levels faster after application of an airpuff startle. Using in situ hybridization, no changes in CRF(1) receptor mRNA expression were detected in parietal cortex, basolateral amygdala, or cerebellum after chronic treatment with CP-154,526. A dose-dependent decrease in CRF mRNA expression was observed in the hypothalamic paraventricular nucleus (PVN) and the Barrington's nucleus, an effect that was significant at the high but not the low dose of CP-154,526. CP-154,526 did not alter central CRF(2A) receptor binding or mRNA expression, or urocortin mRNA expression. The present findings suggest that chronic administration of CP-154, 526 produces anxiolytic-like effects but no evidence of adrenal insufficiency. Previous postmortem studies revealed increased CRF peptide and mRNA levels in the PVN of depressed patients, which may mediate the hyperactivity of the hypothalamic-pituitary-adrenal axis observed in such patients. In view of a possible use for CRF(1) receptor antagonists in the treatment of depression, the present finding that CP-154,526 decreases CRF synthesis in the PVN is of considerable interest.

Effects of two acute stressors on the anxiolytic efficacy of chlordiazepoxide

RATIONALE

Limited published data show that drug efficacy can be influenced by stressors. Thus, drug testing in stressed animals may unravel important variables determining drug effects.

OBJECTIVES

The experiments tested the anxiolytic efficacy of the benzodiazepine chlordiazepoxide under conditions of acute stress.

METHODS

Previously group-housed rats were injected with 0, 3, and 10 mg/kg chlordiazepoxide, thereafter being exposed to two types of stress: novelty (transfer to an individual cage) and social defeat. Controls were group-housed animals. Anxiety was assessed on the plus maze.

RESULTS

Speed of locomotion was increased by chlordiazepoxide in both stressed groups but not in controls. Chlordiazepoxide exerted a marked reduction in anxiety in controls and defeated rats but not in novelty exposed animals. The effects of novelty exposure were considerably weaker when drug testing was performed 24 h later.

CONCLUSIONS

Stress exposure had an impact on the behavioral effects of chlordiazepoxide. Changes in locomotor activity induced by the drug appear to depend on the presence of a stressor, while anxiolytic efficacy appears to depend on the type of the stressor. Since it has been shown that drug efficacy changes in a variety of behavioral situations and drug classes, it is suggested that experimental background is an important variable in determining behavioral effects of drugs.

Differential effect of a polyherbal formulation-OB-200G in male and female mice subjected to forced swim stress

The antistress effect of a polyherbal formulation-OB-200G (500 mg/kg. p.o.) was studied in both male and female mice subjected to forced swim stress. Fluoxetine (10 mg/kg, i.p.) was chosen as standard drug for comparison. Exposure of mice to chronic stress regime resulted in decreased body weight in both male and female mice, increased sweetened food intake, anxiety, depression and locomotor activity in stressed female mice as compared to unstressed control (normal) mice. Treatment with OB-200G resulted in a further decrease in body weight, increased food intake and locomotor activity in both stressed male and female mice. It also reduced immobility time, decreased latency to enter and increased number of entries and time spent in mirror chamber in stressed female mice. Administration of fluoxetine (10 mg/kg, i.p.) decreased body weight and food intake in both stressed male and female mice. Fluoxetine treatment also increased time spent in mirror chamber and decreased immobility time in stressed female mice. Thus, like fluoxetine, OB-200G decreased body weight and produced antianxiety and antidepressant effects in stressed female mice and may prove beneficial in obese patients reported to be more susceptible to stress-related psychological disorders.

Ginkgo biloba extract (EGb 761) and CNS functions: basic studies and clinical applications

The effects of EGb 761 on the CNS underlie one of its major therapeutic indications; i.e., individuals suffering from deteriorating cerebral mechanisms related to age-associated impairments of memory, attention and other cognitive functions. EGb 761 is currently used as symptomatic treatment for cerebral insufficiency that occurs during normal ageing or which may be due to degenerative dementia, vascular dementia or mixed forms of both, and for neurosensory disturbances. Depressive symptoms of patients with Alzheimer's disease (AD) and aged non-Alzheimer patients may also respond to treatment with EGb 761 since this extract has an "anti-stress" effect. Basic and clinical studies, conducted both in vitro and in vivo, support these beneficial neuroprotective effects of EGb 761. EGb 761 has several major actions; it enhances cognition, improves blood rheology and tissue metabolism, and opposes the detrimental effects of ischaemia. Several mechanisms of action are useful in explaining how EGb 761 benefits patients with AD and other age-related, neurodegenerative disorders. In animals, EGb 761 possesses antioxidant and free radical-scavenging activities, it reverses age-related losses in brain alpha 1-adrenergic, 5-HT1A and muscarinic receptors, protects against ischaemic neuronal death, preserves the function of the hippocampal mossy fiber system, increases hippocampal high-affinity choline uptake, inhibits the down-regulation of hippocampal glucocorticoid receptors, enhances neuronal plasticity, and counteracts the cognitive deficits that follow stress or traumatic brain injury. Identified chemical constituents of EGb 761 have been associated with certain actions. Both flavonoid and ginkgolide constituents are involved in the free radical-scavenging and antioxidant effects of EGb 761 which decrease tissue levels of reactive oxygen species (ROS) and inhibit membrane lipid peroxidation. Regarding EGb 761-induced regulation of cerebral glucose utilization, bilobalide increases the respiratory control ratio of mitochondria by protecting against uncoupling of oxidative phosphorylation, thereby increasing ATP levels, a result that is supported by the finding that bilobalide increases the expression of the mitochondrial DNA-encoded COX III subunit of cytochrome oxidase. With regard to its "anti-stress" effect, EGb 761 acts via its ginkgolide constituents to decrease the expression of the peripheral benzodiazepine receptor (PBR) of the adrenal cortex.

[Correction by common sea buckthorn bark and sprout extracts of hormonal and metabolic disturbances during stress in rats]

Long-term administration of the common sea buckthorn bark and sprout extract improves the hormonal-metabolic organism status in rats disturbed by a stress factor (immobilization). The drug administration led to normalization of the altered functional activity indices of the neuro-endocrine system (disturbed adrenocorticotropin, 11-deoxycortisol, insulin, urea, and glucose levels) by affecting the production of glucocorticoids and increasing the hypothalamus sensitivity with respect to regulatory signals.

Exploratory behaviour and grooming after repeated restraint and chronic mild stress: effect of desipramine

In a previous study, we have recently shown that chronic treatment with desipramine either reduced or potentiated the locomotor response to the dopamine D(2)-like receptor agonist quinpirole, a behavioural response mediated by the mesolimbic dopamine system, depending on whether the animals were subjected, respectively, to repeated restraint or to chronic mild stress (different stressors randomly presented). In this study, we examined the interaction between prolonged exposure to either repeated restraint stress or chronic mild stress with the chronic administration of the antidepressant desipramine on two spontaneous behaviours, in which an involvement of the mesolimbic dopamine system has been suggested: novelty-induced exploratory activity and grooming. Exploratory activity in the open field was reduced by chronic mild stress regardless of the drug treatment, while it was not influenced by restraint stress. Desipramine reduced exploratory activity in rats subjected to restraint stress. Restraint stress increased grooming and desipramine reversed this effect, while increasing grooming in the chronic mild stress group. These findings suggest that antidepressants exert their effect by opposing the modifications induced by stress. The available experimental evidence is consistent with the hypothesis that an important role in the observed behavioural changes is played by the mesolimbic dopamine system.

Protective effect of a traditional Japanese medicine, Bu-zhong-yi-qi-tang (Japanese name: Hochu-ekki-to), on the restraint stress-induced susceptibility against Listeria monocytogenes

In this study, the effect of traditional Japanese (Chinese) medicine, Bu-zhong-yi-qi-tang (Japanese name: Hochu-ekki-to, HOT), on the restraint stress treatment (RST)-induced susceptibility against Listeria monocytogenes (L. monocytogenes) was examined. When RST was performed every day for 10 h from the day of infection, the bacterial numbers were increased at 3 and 5 days after the infection. Oral pretreatment with HOT for 7 days prevented such increases. Pretreatment with HOT prevented the suppression of antigen-specific IFN-gamma production by RST. HOT also prevented suppression of macrophage accumulation, including MHC-class II positives, in the peritoneal cavity and their bactericidal activity by RST. HOT suppressed the serum corticosterone level elevated by RST in infected mice. Taken together, the suppression of corticosterone using HOT participates in the prevention of suppressions of the bactericidal activity of macrophages, migration of macrophages and antigen-specific IFN-gamma production of Th1 cells by RST. Our findings suggest that HOT is a useful drug for patients suffering from stress disease to reduce the susceptibility to bacterial infection.

Morphine-induced suppression of saccharin intake is correlated with elevated corticosterone levels

Rats suppress intake of a saccharin conditioned stimulus (CS) when paired with a drug of abuse. This phenomenon, however, is not uniform across all subjects and is greater following exposure to stress and in animals that more readily self-administer drugs of abuse. The present study was designed to examine these individual differences in intake suppression following seven saccharin-morphine pairings. Plasma corticosterone also was evaluated both before and after conditioning in order to determine whether the magnitude of CS suppression is, or is not, related to circulating corticosterone levels. The findings indicated that, while all rats were exposed to the same number of saccharin-morphine pairings, only half of these animals actually suppressed intake of the saccharin CS. Moreover, the results showed that greater suppression of CS intake was associated with higher corticosterone levels at test (r=-0.84, P<0.0001). Taken together, the results demonstrate that individual differences affect not only the reduction in CS intake following taste-drug pairings, but also the associated cue-induced elevation in circulating corticosterone.

Effects of chronic mild stress (CMS) on thyroid hormone function in two rat strains

This work was carried out to assess the effects of chronic mild stress (CMS) on thyroid function. The CMS model produced an anhedonic effect (reduced preference to sucrose) in Sprague-Dawley and Wistar rats and this effect was reversed by imipramine (IMI) treatment. The effects of CMS on thyroid function were assessed by measuring tT4 (total Thyroxine), tT3 (total Triiodothyronine), TSH (Thyroid Stimulating Hormone) and fT4 (free Thyroxine) serum levels with appropriate immunoassays. CMS increased tT4 and tT3 serum levels in Sprague-Dawley and Wistar rats, but not TSH and fT4 serum levels. Imipramine (IMI) treatment normalized tT4 values. Albumin which binds a fraction of peripheral tT4 and tT3 was also significantly increased in response to CMS, possibly contributing to tT4 and tT3 elevations. The above findings suggest an impact of CMS on thyroid function, especially in tT4 values the changes being reversed with IMI treatment.