Effects of Atomoxetine on Levels of Monoamines and Related Substances in Discrete Brain Regions in Mice Intermittently Deprived of Rapid Eye Movement Sleep

Sleep and Pain: A Role for the Anterior Cingulate Cortex, Nucleus Accumbens, and Dopamine in the Increased Pain Sensitivity Following Sleep Restriction

Persistent pain conditions and sleep disorders are public health problems worldwide. It is widely accepted that sleep disruption increases pain sensitivity; however, the underlying mechanisms are poorly understood. In this study, we used a protocol of 6 hours a day of total sleep deprivation for 3 days in rats to advance the understanding of these mechanisms. We focused on gender differences and the dopaminergic mesocorticolimbic system. The findings demonstrated that sleep restriction (SR) increased pain sensitivity in a similar way in males and females, without inducing a significant stress response. This pronociceptive effect depends on a nucleus accumbens (NAc) neuronal ensemble recruited during SR and on the integrity of the anterior cingulate cortex (ACC). Data on indirect dopaminergic parameters, dopamine transporter glycosylation, and dopamine and cyclic adenosine monophosphate (AMP)-regulated phosphoprotein-32 phosphorylation, as well as dopamine, serotonin, and norepinephrine levels, suggest that dopaminergic function decreases in the NAc and ACC after SR. Complementarily, pharmacological activation of dopamine D2, but not D1 receptors either in the ACC or in the NAc prevents SR from increasing pain sensitivity. The ACC and NAc are the main targets of dopaminergic mesocorticolimbic projections with a key role in pain modulation. This study showed their integrative role in the pronociceptive effect of SR, pointing to dopamine D2 receptors as a potential target for pain management in patients with sleep disorders. These findings narrow the focus of future studies on the mechanisms by which sleep impairment increases pain sensitivity. PERSPECTIVE: This study demonstrates that the pronociceptive effect of SR affects similarly males and females and depends on a NAc neuronal ensemble recruited during SR and on the integrity of the ACC. Findings on dopaminergic function support dopamine D2 receptors as targets for pain management in sleep disorders patients.

Xiaoyao Pill improves the Affective Dysregulation of Sleep-deprived Female Mice by inhibiting Brain Injury and regulating the Content of Monoamine Neurotransmitter

BACKGROUND

Sleep curtailment is a serious problem in many societies. Clinical evidence has shown that sleep deprivation is associated with mood dysregulation, formation of false memory, cardio-metabolic risk factors and outcomes, inflammatory disease risk, and all-cause mortality. The affective disorder dysregulation caused by insufficient sleep has become an increasingly serious health problem. However, to date, not much attention has been paid to the mild affective dysregulation caused by insufficient sleep, and there is no clear and standard therapeutic method to treat it. The Xiaoyao Pill is a classic Chinese medicinal formula, with the effect of dispersing stagnated hepatoqi, invigorating the spleen, and nourishing the blood. Therefore, it is most commonly used to treat gynecological diseases in China. In the present study, the effects of the Xiaoyao Pill on affective dysregulation of sleep-deprived mice and its underlying molecular mechanisms were investigated.

METHODS

Forty adult female mice were used in the present study. The sleep deprivation model was established by improving the multi-platform water environment method. After 7 consecutive days of sleep deprivation, the mice were administrated low (LXYP, 0.32mg/kg) and high (HXYP, 0.64 mg/kg) doses of the Xiaoyao Pill for two weeks. Then, the body weight, behavioral deficits, and histopathology were evaluated. Meanwhile, the expression of c-fos protein and the concentrations of monoamine neurotransmitters in the hippocampus and prefrontal cortex were determined after two weeks of treatment.

RESULTS

Xiaoyao Pill treatment significantly increased body weight and sucrose consumption and decreased the irritability scores of the sleep-deprived mice. Meanwhile, Xiaoyao Pill treatment prevented brain injury and inhibited the expression of c-fos protein in the hippocampus and prefrontal cortex. In addition, HXYP treatment significantly upregulated the levels of NE in the hippocampus and prefrontal cortex (p < 0.01). LXYP treatment significantly up-regulated the levels of 5-HT in the prefrontal cortex. Meanwhile, both HXYP and LXYP treatment significantly up-regulated the levels of DA in the prefrontal cortex (p < 0.05 or p < 0.01) of sleep-deprived mice.

CONCLUSIONS

The present study demonstrates that Xiaoyao Pill treatment prevented the behavioral deficits of mice induced by sleep deprivation by promoting the recovery of brain tissue injury and up-regulating the levels of NE, 5-HT, and DA in the brain tissue.

Involvement of the Hippocampal Alpha2A-Adrenoceptors in Anxiety-Related Behaviors Elicited by Intermittent REM Sleep Deprivation-Induced Stress in Mice

Attention deficit/hyperactivity disorder (AD/HD) is a neurodevelopmental disorder characterized by inattention, hyperactivity, and impulsivity. In patients with AD/HD, a decrease in the total and rapid eye movement (REM) sleep times has been observed. We have previously reported that mice with REM sleep deprivation-induced stress (REMSD) may show the hyperactivity- and inattention-like symptoms of AD/HD. However, in this model, impulsivity has not yet been investigated. Impulsivity and anxiety-related behaviors are evaluated by the elevated plus maze test (EPM). In this study, we investigated whether REMSD causes changes in the EPM and expression of alpha2A-adrenoceptors in the hippocampus and frontal cortex in a mouse model. Mice were deprived of REM sleep intermittently using the small-platform method (20 h/d) for 3 d. The time spent in the open arm and the expression levels of alpha2A-adrenoceptor in the hippocampus were significantly increased and decreased, respectively, by the REMSD. The time spent in the open arm was significantly limited by oxymetazoline (an alpha2A-adrenoceptor agonist), methylphenidate, and atomoxetine, which are clinically used to treat AD/HD. Moreover, the positive effects of oxymetazoline were attenuated by yohimbine and BRL44408, which are selective alpha2- and alpha2A-adrenoceptor antagonists, respectively. These results suggest that the increase in the time spent in the open arm induced by REMSD may serve as a model of impulsivity in AD/HD. Furthermore, the REMSD eliciting impulsivity-like behavior and the low-levels of anxiety may be linked to alpha2A-adrenoceptor signaling, as indicated by a decrease in alpha2A-adrenoceptor signaling, particularly in the mouse hippocampus.

Sleep deprivation of rats increases postsurgical expression and activity of L-type calcium channel in the dorsal root ganglion and slows recovery from postsurgical pain

Perioperative sleep disturbance is a risk factor for persistent pain after surgery. Clinical studies have shown that patients with insufficient sleep before and after surgery experience more intense and long-lasting postoperative pain. We hypothesize that sleep deprivation alters L-type calcium channels in the dorsal root ganglia (DRG), thus delaying the recovery from post-surgical pain. To verify this hypothesis, and to identify new predictors and therapeutic targets for persistent postoperative pain, we first established a model of postsurgical pain with perioperative sleep deprivation (SD) by administering hind paw plantar incision to sleep deprivation rats. Then we conducted behavioral tests, including tests with von Frey filaments and a laser heat test, to verify sensory pain, measured the expression of L-type calcium channels using western blotting and immunofluorescence of dorsal root ganglia (an important neural target for peripheral nociception), and examined the activity of L-type calcium channels and neuron excitability using electrophysiological measurements. We validated the findings by performing intraperitoneal injections of calcium channel blockers and microinjections of dorsal root ganglion cells with adeno-associated virus. We found that short-term sleep deprivation before and after surgery increased expression and activity of L-type calcium channels in the lumbar dorsal root ganglia, and delayed recovery from postsurgical pain. Blocking these channels reduced impact of sleep deprivation. We conclude that the increased expression and activity of L-type calcium channels is associated with the sleep deprivation-mediated prolongation of postoperative pain. L-type calcium channels are thus a potential target for management of postoperative pain.

Increased Mmp/Reck Expression Ratio Is Associated with Increased Recognition Memory Performance in a Parkinson's Disease Animal Model

Parkinson's disease (PD) is the second most prevalent neurodegenerative disorder worldwide. Among its non-motor symptoms, sleep disorders are extremely common, being linked to cognitive and memory disruption. The microenvironment, particularly the extracellular matrix (ECM), is deeply involved in memory consolidation as well as in neuropathological processes, such as inflammation, damage to the blood-brain barrier and neuronal death. To better understand ECM dynamics in PD memory disturbances, we investigated the orchestrated expression of Mmps (Mmp-3, Mmp-7, and Mmp-9) and their modulators (Reck and Timp-3) in a rotenone-induced PD model. Also, we introduced an additional intervention in the memory process through rapid eye movement sleep deprivation (REMSD). We observed a REMSD-induced trend in reversing the memory impairment caused by rotenone administration. Associated to this phenotype, we observed a significant increase in Mmp-7/Reck and Mmp-9/Reck mRNA expression ratio in the substantia nigra and Mmp-9/Reck ratio in the hypothalamus. Moreover, the positive correlation of Mmp/Reck expression ratios between the substantia nigra and the striatum, observed upon rotenone infusion, was reversed by REMSD. Taken together, our results suggest a potential orchestrated association between an increase in Mmp-7 and Mmp-9/Reck expression ratios in the substantia nigra and a possible positive effect on cognitive performance in subjects affected by PD.

Animal Models for Elucidation of the Mechanisms of Neuropsychiatric Disorders Induced by Sleep and Dietary Habits

Numerous changes in human lifestyle in modern life increase the risk of disease. Especially, modern sleep and dietary habits are crucial factors affecting lifestyle disease. In terms of sleep, decreases in total sleep time and in rapid eye movement sleep time have been observed in attention-deficit/hyperactivity disorder (ADHD) patients. From a dietary perspective, mastication during eating has several good effects on systemic, mental, and physical functions of the body. However, few animal experiments have addressed the influence of this decline in sleep duration or of long-term powdered diet feeding on parameters reflecting systemic health. In our studies, we examined both the influence of intermittent sleep deprivation (SD) treatment and long-term powdered diet feeding on emotional behavior in mice, and focused on the mechanisms underlying these impaired behaviors. Our findings were as follows: SD treatment induced hypernoradrenergic and hypodopaminergic states within the frontal cortex. Furthermore, hyperactivity and an explosive number of jumps were observed. Both the hypernoradrenergic state and the jumps were improved by treatment with ADHD therapeutic drugs. On the other hand, long-term powdered diet feeding increased social interaction behaviors. The feeding affected the dopaminergic function of the frontal cortex. In addition, the long-term powdered diet fed mice presented systemic illness signs, such as elevations of blood glucose, and hypertension. This review, describing the SD mice and long-term powdered diet fed mice can be a useful model for elucidation of the mechanism of neuropsychiatric disorders or the discovery of new therapeutic targets in combatting effects of the modern lifestyle.