Long-term swimming in an inescapable stressful environment attenuates the stimulatory effect of endurance swimming on duodenal calcium absorption in rats

Atomoxetine and escitalopram migrate the derangement of the temporomandibular joint morphologic and histologic changes in rats exposed to stress-induced depression

PURPOSE

The purpose of this in vivo study was to determine the effects of stress-induced depression and antidepressants on depressive-like behavior, microstructure, and histomorphology of the temporomandibular joint (TMJ) using rats.

METHODS

Experimentally induced depression in rats was created before being treated with two antidepressants; escitalopram (selective-serotonin-reuptake inhibitors) and atomoxetine (norepinephrine-reuptake inhibitors). Micro-computed tomography (Micro-CT) was performed to measure the change in bone volume and bone porosity of the condyle. Further histological evaluation of the condylar cartilage was performed.

RESULTS

Micro-CT scanning revealed a decrease in bone volume in the depression group. The bone porosity percentage significantly increased in both the escitalopram and atomoxetine groups compared with the control group and the depression group. Histopathological analysis showed increased thickness of cartilage layers in the depression group. In the atomoxetine group, there was a significant increase in the pre-hypertrophic and hypertrophic layer thickness and cell count, but a significant decrease in proteoglycans.

CONCLUSION

The present study findings indicated the change in TMJ characteristics, especially on the superficial part of the condylar head in the depression group. Concerning the applicability of the different antidepressants, depression with the treatment of atomoxetine has the most disadvantages due to bone porosity and cartilaginous condyle changes.

Positive long-term outcomes from presuckling calcium supplementation in lactating rats and the offspring

Adequate dietary calcium intake and the enhanced intestinal calcium absorption in lactating mothers have long been postulated to prevent maternal bone loss and benefit neonatal bone growth. We recently showed that calcium supplementation just before breastfeeding efficiently alleviated lactation-induced bone loss in dams as well as increased milk calcium concentration, which led to higher bone mineral density (BMD) in the newborns. Herein, we further elaborated in detail how presuckling calcium supplements worked in lactating rats and how they benefited bone growth in the offspring. As revealed by bone histomorphometry, presuckling supplement with calcium alone reduced the osteoclast surface and active erosion surface, leading to an increase in trabecular thickness without changes in trabecular separation or number in dams. The beneficial effects of presuckling calcium supplements, particularly the regimen containing glucose and galactose that enhanced intestinal calcium absorption, were found to last for 3 mo postweaning, although it could not restore estrogen-deficient osteopenia induced by ovariectomy. Regarding the neonatal benefits, pups nursed by calcium-supplemented dams exhibited increases in trabecular BMD, which could be observed even at the age of 27 wk. Bone elongation was also greater in pups of calcium-supplemented dams, which was due possibly to accelerated growth plate chondrocyte turnover. It could be concluded that calcium supplements markedly diminished the lactation-induced osteopenia in dams and positively affected BMD and bone elongation in growing rats. Therefore, presuckling calcium supplementation in lactating mothers is an effective strategy for promoting a long-lasting high bone density for both mother and the offspring.

Voluntary wheel running mitigates the stress-induced bone loss in ovariectomized rats

In estrogen-deficient rodents with osteopenia, repetitive exposure to mild-to-moderate stress, which mimics the chronic aversive stimuli (CAS) of the modern urban lifestyle in postmenopausal women, has been hypothesized to cause the bone microstructure to further deteriorate. Recently, we have provided evidence in rats that voluntary impact exercise, e.g., wheel running, is as effective as pharmacological treatments for stress-induced anxiety and depression. The present study, therefore, aims to investigate whether a 4-week CAS exposure aggravates trabecular bone loss in ovariectomized (Ovx) rats, and whether CAS-induced bone loss can be rescued by voluntary wheel running. CAS was found to elevate the serum levels of corticosterone, a stress hormone from the adrenal gland. Dual energy X-ray absorptiometry revealed a decrease in bone mineral content (BMC) in the tibiae of CAS-exposed Ovx rats as compared to the CAS-free Ovx rats (control), while having no detectable effect on bone mineral density (BMD). Bone histomorphometric analysis of the proximal tibial metaphysis showed that CAS decreased trabecular bone volume and increased trabecular separation, which were completely restored to the baseline values of Ovx rats by voluntary wheel running. This CAS-induced trabecular bone loss in Ovx rats was probably due to an enhancement of osteoclast-mediated bone resorption, as indicated by increases in osteoclast surface and active erosion surface. Moreover, wheel running as well as non-impact exercise (endurance swimming) effectively increased the tibial BMD and BMC of CAS-exposed Ovx rats. It can be concluded that exercise is an effective intervention in mitigating CAS-induced bone loss in estrogen-deficient rats.

Anxiolytic-like effects of mitragynine in the open-field and elevated plus-maze tests in rats

The effects of mitragynine on anxiety-related behaviours in the open-field and elevated plus-maze tests were evaluated. Male Sprague-Dawley rats were orally treated with mitragynine (10, 20 and 40 mg/kg) or diazepam (10 mg/kg) 60 min before behavioural testing. Mitragynine doses used in this study were selected on the basis of approximately human equivalent doses with reference to our previous literature reports. Acute administration of mitragynine (10, 20 and 40 mg/kg) or diazepam (10 mg/kg) increased central zone and open arms exploration in the open-field and elevated plus-maze tests respectively. These anxiolytic-like effects of mitragynine were effectively antagonized by intraperitoneal administration of naloxone (2 mg/kg), flumazenil (10 mg/kg), sulpiride (0.5 mg/kg) or SCH 23390 (0.02 mg/kg) 15 min before mitragynine treatments. These findings reveal that the acute administration of mitragynine produces anxiolytic-like effects and this could be possibly attributed to the interactions among opioidergic, GABAergic and dopaminergic systems in brain regions involved in anxiety.

Influence of training frequency on serum concentrations of some essential trace elements and electrolytes in male swimmers

Elemental fluctuations during physical performances have been a point of interest. This study was designed to investigate the effect of swimming frequency on serum concentrations of some trace elements (chromium, iron, copper, zinc, selenium) and electrolytes (sodium, magnesium, potassium, calcium). Three groups of different-level male swimmers were included in the study, as elite swimmers (n = 14), amateur swimmers (n = 11), and sedentary individuals (n = 10). Elite and amateur swimmer groups followed a 3-week training program. At the end of the period, all volunteers were subjected to a controlled swimming test, and blood samples were collected at the beginning of (pre-test), immediately after (post-test), and 1 h after this activity. Element concentrations were determined by inductively coupled plasma mass spectrometry using a dilute and shoot procedure. Apart from the swimming test applied, pre-test calcium and potassium levels were higher in elite swimmers compared to amateurs and controls. The difference in pre-test levels of these elements can be associated with adaptive mechanisms emerged by the frequent training. Regarding the test applied, changes in magnesium, calcium, copper, zinc, and selenium levels exhibited a common pattern in all study groups, with higher post-test serum concentrations. Another point of note was a drop of copper, zinc, and selenium levels at 1 h after the test in elite swimmers. The decrease in serum zinc was also observed in the other groups. Results highlight the value of regular control of elemental status to provide insight into transient effects and deficiencies.

Beneficial effects of fluoxetine, reboxetine, venlafaxine, and voluntary running exercise in stressed male rats with anxiety- and depression-like behaviors

Rodents exposed to mild but repetitive stress may develop anxiety- and depression-like behaviors. Whether this stress response could be alleviated by pharmacological treatments or exercise interventions, such as wheel running, was unknown. Herein, we determined anxiety- and depression-like behaviors in restraint stressed rats (2h/day, 5 days/week for 4 weeks) subjected to acute diazepam treatment (30min prior to behavioral test), chronic treatment with fluoxetine, reboxetine or venlafaxine (10mg/kg/day for 4 weeks), and/or 4-week voluntary wheel running. In elevated plus-maze (EPM) and forced swimming tests (FST), stressed rats spent less time in the open arms and had less swimming duration than the control rats, respectively, indicating the presence of anxiety- and depression-like behaviors. Stressed rats also developed learned fear as evaluated by elevated T-maze test (ETM). Although wheel running could reduce anxiety-like behaviors in both EPM and ETM, only diazepam was effective in the EPM, while fluoxetine, reboxetine, and venlafaxine were effective in the ETM. Fluoxetine, reboxetine, and wheel running, but not diazepam and venlafaxine, also reduced depression-like behavior in FST. Combined pharmacological treatment and exercise did not further reduce anxiety-like behavior in stressed rats. However, stressed rats treated with wheel running plus reboxetine or venlafaxine showed an increase in climbing duration in FST. In conclusion, regular exercise (voluntary wheel running) and pharmacological treatments, especially fluoxetine and reboxetine, could alleviate anxiety- and depression-like behaviors in stressed male rats.

Upregulated mRNA levels of SERT, NET, MAOB, and BDNF in various brain regions of ovariectomized rats exposed to chronic aversive stimuli

Estrogen deficiency increases the risk of anxiety and mood disorders, presumably by deranging metabolism of the monoamine neurotransmitters and the expression of their reuptake transporters in the brain. Although estrogen-deficient individuals were also susceptible to stress, little was known regarding the effect of stress on the levels of transcripts related to brain monoamine metabolism. Herein, we used quantitative real-time PCR to quantify the mRNA levels of serotonin reuptake transporter (SERT), norepinephrine transporter (NET), monoamine oxidase-B (MAOB), tryptophan hydroxylase (TPH), and tyrosine hydroxylase (TH) in various brain regions of ovariectomized (OVX) rats which had been exposed for 4 weeks to chronic aversive stimuli (CAS), such as water deprivation, cage tilt, and illumination. We found that CAS induced stress responses in OVX rats as indicated by increases in the adrenal gland weight and sucrose intake. After CAS exposure, mRNA levels of SERT and NET were upregulated in the frontal cortex, hippocampus, amygdala, and periaqueductal gray. In addition, CAS also increased the mRNA levels of MAOB, an enzyme for dopamine degradation, in the same brain regions. However, CAS did not alter the mRNA levels of TPH or TH, both of which are rate-limiting enzymes for the synthesis of serotonin and norepinephrine in the dorsal raphé and locus coeruleus, respectively. Interestingly, mRNA expression of brain-derived neurotrophic factor precursor was upregulated in the hippocampus of CAS-exposed OVX rats, suggesting a compensatory mechanism which might counteract the stress-induced depression. Therefore, the present data have provided evidence to explain how stress affected brain monoamine metabolism in estrogen-deficient stressed patients.