The contribution of periaqueductal gray in the regulation of physiological and pathological behaviors.

Periaqueductal gray (PAG), an integration center for neuronal signals, is located in the midbrain and regulates multiple physiological and pathological behaviors, including pain, defensive and aggressive behaviors, anxiety and depression, cardiovascular response, respiration, and sleep-wake behaviors. Due to the different neuroanatomical connections and functional characteristics of the four functional columns of PAG, different subregions of PAG synergistically regulate various instinctual behaviors. In the current review, we summarized the role and possible neurobiological mechanism of different subregions of PAG in the regulation of pain, defensive and aggressive behaviors, anxiety, and depression from the perspective of the up-down neuronal circuits of PAG. Furthermore, we proposed the potential clinical applications of PAG. Knowledge of these aspects will give us a better understanding of the key role of PAG in physiological and pathological behaviors and provide directions for future clinical treatments.

Optochemical control of slow-wave sleep in the nucleus accumbens of male mice by a photoactivatable allosteric modulator of adenosine A2A receptors.

Optochemistry, an emerging pharmacologic approach in which light is used to selectively activate or deactivate molecules, has the potential to alleviate symptoms, cure diseases, and improve quality of life while preventing uncontrolled drug effects. The development of in-vivo applications for optochemistry to render brain cells photoresponsive without relying on genetic engineering has been progressing slowly. The nucleus accumbens (NAc) is a region for the regulation of slow-wave sleep (SWS) through the integration of motivational stimuli. Adenosine emerges as a promising candidate molecule for activating indirect pathway neurons of the NAc expressing adenosine A2A receptors (A2ARs) to induce SWS. Here, we developed a brain-permeable positive allosteric modulator of A2ARs (A2AR PAM) that can be rapidly photoactivated with visible light (λ > 400 nm) and used it optoallosterically to induce SWS in the NAc of freely behaving male mice by increasing the activity of extracellular adenosine derived from astrocytic and neuronal activity.

Whole-brain monosynaptic inputs to lateral periaqueductal gray glutamatergic neurons in mice.

OBJECTIVE: The lateral periaqueductal gray (LPAG), which mainly contains glutamatergic neurons, plays an important role in social responses, pain, and offensive and defensive behaviors. Currently, the whole-brain monosynaptic inputs to LPAG glutamatergic neurons are unknown. This study aims to explore the structural framework of the underlying neural mechanisms of LPAG glutamatergic neurons. METHODS: This study used retrograde tracing systems based on the rabies virus, Cre-LoxP technology, and immunofluorescence analysis. RESULTS: We found that 59 nuclei projected monosynaptic inputs to the LPAG glutamatergic neurons. In addition, seven hypothalamic nuclei, namely the lateral hypothalamic area (LH), lateral preoptic area (LPO), substantia innominata (SI), medial preoptic area, ventral pallidum, posterior hypothalamic area, and lateral globus pallidus, projected most densely to the LPAG glutamatergic neurons. Notably, we discovered through further immunofluorescence analysis that the inputs to the LPAG glutamatergic neurons were colocalized with several markers related to important neurological functions associated with physiological behaviors. CONCLUSION: The LPAG glutamatergic neurons received dense projections from the hypothalamus, especially nuclei such as LH, LPO, and SI. The input neurons were colocalized with several markers of physiological behaviors, which show the pivotal role of glutamatergic neurons in the physiological behaviors regulation by LPAG.

Adenosine and P1 receptors: Key targets in the regulation of sleep, torpor, and hibernation.

Sleep, torpor, and hibernation are three distinct hypometabolic states. However, they have some similar physiological features, such as decreased core body temperature and slowing heart rate. In addition, the accumulation of adenosine seems to be a common feature before entry into these three states, suggesting that adenosine and its receptors, also known as P1 receptors, may mediate the initiation and maintenance of these states. This review, therefore, summarizes the current research on the roles and possible neurobiological mechanisms of adenosine and P1 receptors in sleep, torpor, and hibernation. Understanding these aspects will give us better prospects in sleep disorders, therapeutic hypothermia, and aerospace medicine.

Roles of Neuropeptides in Sleep-Wake Regulation.

Sleep and wakefulness are basic behavioral states that require coordination between several brain regions, and they involve multiple neurochemical systems, including neuropeptides. Neuropeptides are a group of peptides produced by neurons and neuroendocrine cells of the central nervous system. Like traditional neurotransmitters, neuropeptides can bind to specific surface receptors and subsequently regulate neuronal activities. For example, orexin is a crucial component for the maintenance of wakefulness and the suppression of rapid eye movement (REM) sleep. In addition to orexin, melanin-concentrating hormone, and galanin may promote REM sleep. These results suggest that neuropeptides play an important role in sleep-wake regulation. These neuropeptides can be divided into three categories according to their effects on sleep-wake behaviors in rodents and humans. (i) Galanin, melanin-concentrating hormone, and vasoactive intestinal polypeptide are sleep-promoting peptides. It is also noticeable that vasoactive intestinal polypeptide particularly increases REM sleep. (ii) Orexin and neuropeptide S have been shown to induce wakefulness. (iii) Neuropeptide Y and substance P may have a bidirectional function as they can produce both arousal and sleep-inducing effects. This review will introduce the distribution of various neuropeptides in the brain and summarize the roles of different neuropeptides in sleep-wake regulation. We aim to lay the foundation for future studies to uncover the mechanisms that underlie the initiation, maintenance, and end of sleep-wake states.

Discontinuous Track Recognition System Based on PolyLaneNet for Darwin-op2 Robot.

This paper proposes and demonstrates a single-line discontinuous track recognition system by associating the track recognition problem of a humanoid robot with the lane detection problem. The proposal enables the robot to achieve stable running on the single-line discontinuous track. The system consists of two parts: the robot end and the graphics computing end. The robot end is responsible for collecting track information and the graphics computing end is responsible for high-performance computing. These two parts use the TCP for communication. The graphics computing side uses PolyLaneNet lane detection algorithm to train the track image captured from the first perspective of the darwin-op2 robot as the data set. In the inference, the robot end sends the collected tracking images to the graphics calculation end and uses the graphics processor to accelerate the calculation. After obtaining the motion vector, it is transmitted back to the robot end. The robot end parses the motion vector to obtain the motion information of the robot so that the robot can achieve stable running on the single-line discontinuous track. The proposed system realizes the direct recognition of the first perspective image of the robot and avoids the problems of poor stability, inability of identifying curves and discontinuous lines, and other problems in the traditional line detection method. At the same time, this system adopts the method of cooperative work between the PC side and the robot by deploying the algorithm with high computational requirements on the PC side. The data transmission is carried out by stable TCP communication, which makes it possible for the robot equipped with weak computational controllers to use deep-learning-related algorithms. It also provides ideas and solutions for deploying deep-learning-related algorithms on similar low computational robots.

Role of Dorsomedial Hypothalamus GABAergic Neurons in Sleep-Wake States in Response to Changes in Ambient Temperature in Mice.

Good sleep quality is essential for maintaining the body's attention during wakefulness, which is easily affected by external factors such as an ambient temperature. However, the mechanism by which an ambient temperature influences sleep-wake behaviors remains unclear. The dorsomedial hypothalamus (DMH) has been reported to be involved in thermoregulation. It also receives projection from the preoptic area, which is an important region for sleep and energy homeostasis and the suprachiasmatic nucleus-a main control area of the clock rhythm. Therefore, we hypothesized that the DMH plays an important role in the regulation of sleep related to ambient temperatures. In this study, we found that cold exposure (24/20/16/12 °C) increased wakefulness and decreased non-rapid eye movement (NREM) sleep, while warm exposure (32/36/40/44 °C) increased NREM sleep and decreased wakefulness compared to 28 °C conditions in wild-type mice. Then, using non-specific and specific apoptosis, we found that lesions of whole DMH neurons and DMH γ-aminobutyric acid (GABA)-ergic neurons induced by caspase-3 virus aggravated the fluctuation of core body temperature after warm exposure and attenuated the change in sleep-wake behaviors during cold and warm exposure. However, chemogenetic activation or inhibition of DMH GABAergic neurons did not affect the sleep-wake cycle. Collectively, our findings reveal an essential role of DMH GABAergic neurons in the regulation of sleep-wake behaviors elicited by a change in ambient temperature.

Adenosine A2A receptor neurons in the olfactory bulb mediate odor-guided behaviors in mice.

Depression, rapid eye movement (REM) sleep behavior disorder, and altered olfaction are often present in Parkinson's disease. Our previous studies demonstrated the role of the olfactory bulb (OB) in causing REM sleep disturbances in depression. Furthermore, adenosine A2A receptors (A2AR) which are richly expressed in the OB, play an important role in the regulation of REM sleep. Caffeine, an adenosine A1 receptors and A2AR antagonist, and other A2AR antagonists were reported to improve olfactory function and restore age-related olfactory deficits. Therefore, we hypothesized that the A2AR neurons in the OB may regulate olfaction or odor-guided behaviors in mice. In the present study, we employed chemogenetics to specifically activate or inhibit neuronal activity. Then, buried food test and olfactory habituation/dishabituation test were performed to measure the changes in the mice's olfactory ability. We demonstrated that activation of OB neurons or OB A2AR neurons shortened the latency of buried food test and enhanced olfactory habituation to the same odors and dishabituation to different odors; inhibition of these neurons showed the opposite effects. Photostimulation of ChR2-expressing OB A2AR neuron terminals evoked inward current in the olfactory tubercle (OT) and the piriform cortex (Pir), which was blocked by glutamate receptor antagonists 2-amino-5-phosphonopentanoic acid and 6-cyano-7nitroquinoxaline-2,3-dione. Collectively, these results suggest that the OB mediates olfaction via A2AR neurons in mice. Moreover, the excitatory glutamatergic release from OB neurons to the OT and the Pir were found responsible for the olfaction-mediated effects of OB A2AR neurons.

Neural circuitry underlying REM sleep: A review of the literature and current concepts.

As one of the fundamental sleep states, rapid eye movement (REM) sleep is believed to be associated with dreaming and is characterized by low-voltage, fast electroencephalographic activity and loss of muscle tone. However, the mechanisms of REM sleep generation have remained unclear despite decades of research. Several models of REM sleep have been established, including a reciprocal interaction model, limit-cycle model, flip-flop model, and a model involving γ-aminobutyric acid, glutamate, and aminergic/orexin/melanin-concentrating hormone neurons. In the present review, we discuss these models and summarize two typical disorders related to REM sleep, namely REM sleep behavior disorder and narcolepsy. REM sleep behavior disorder is a sleep muscle-tone-related disorder and can be treated with clonazepam and melatonin. Narcolepsy, with core symptoms of excessive daytime sleepiness and cataplexy, is strongly connected with orexin in early adulthood.

Ventral pallidal GABAergic neurons control wakefulness associated with motivation through the ventral tegmental pathway.

The ventral pallidum (VP) regulates motivation, drug addiction, and several behaviors that rely on heightened arousal. However, the role and underlying neural circuits of the VP in the control of wakefulness remain poorly understood. In the present study, we sought to elucidate the specific role of VP GABAergic neurons in controlling sleep-wake behaviors in mice. Fiber photometry revealed that the population activity of VP GABAergic neurons was increased during physiological transitions from non-rapid eye movement (non-REM, NREM) sleep to either wakefulness or REM sleep. Moreover, chemogenetic and optogenetic manipulations were leveraged to investigate a potential causal role of VP GABAergic neurons in initiating and/or maintaining arousal. In vivo optogenetic stimulation of VP GABAergic neurons innervating the ventral tegmental area (VTA) strongly promoted arousal via disinhibition of VTA dopaminergic neurons. Functional in vitro mapping revealed that VP GABAergic neurons, in principle, inhibited VTA GABAergic neurons but also inhibited VTA dopaminergic neurons. In addition, optogenetic stimulation of terminals of VP GABAergic neurons revealed that they promoted arousal by innervating the lateral hypothalamus, but not the mediodorsal thalamus or lateral habenula. The increased wakefulness chemogenetically evoked by VP GABAergic neuronal activation was completely abolished by pretreatment with dopaminergic D1 and D2/D3 receptor antagonists. Furthermore, activation of VP GABAergic neurons increased exploration time in both the open-field and light-dark box tests but did not modulate depression-like behaviors or food intake. Finally, chemogenetic inhibition of VP GABAergic neurons decreased arousal. Taken together, our findings indicate that VP GABAergic neurons are essential for arousal related to motivation.

Activation of adenosine A2A receptors in the olfactory tubercle promotes sleep in rodents.

The olfactory tubercle (OT), an important nucleus in processing sensory information, has been reported to change cortical activity under odor. However, little is known about the physiological role and mechanism of the OT in sleep-wake regulation. The OT expresses abundant adenosine A2A receptors (A2ARs), which are important in sleep regulation. Therefore, we hypothesized that the OT regulates sleep via A2ARs. This study examined sleep-wake profiles through electroencephalography and electromyography recordings with pharmacological and chemogenetic manipulations in freely moving rodents. Compared with their controls, activation of OT A2ARs pharmacologically and OT A2AR neurons via chemogenetics increased non-rapid eye movement sleep for 5 and 3 h, respectively, while blockade of A2ARs decreased non-rapid eye movement sleep. Tracing and electrophysiological studies showed OT A2AR neurons projected to the ventral pallidum and lateral hypothalamus, forming inhibitory innervations. Together, these findings indicate that A2ARs in the OT play an important role in sleep regulation.

The Mutual Interaction Between Sleep and Epilepsy on the Neurobiological Basis and Therapy.

BACKGROUND: Sleep and epilepsy are mutually related in a complex, bidirectional manner. However, our understanding of this relationship remains unclear. RESULTS: The literatures of the neurobiological basis of the interactions between sleep and epilepsy indicate that non rapid eye movement sleep and idiopathic generalized epilepsy share the same thalamocortical networks. Most of neurotransmitters and neuromodulators such as adenosine, melatonin, prostaglandin D2, serotonin, and histamine are found to regulate the sleep-wake behavior and also considered to have antiepilepsy effects; antiepileptic drugs, in turn, also have effects on sleep. Furthermore, many drugs that regulate the sleep-wake cycle can also serve as potential antiseizure agents. The nonpharmacological management of epilepsy including ketogenic diet, epilepsy surgery, neurostimulation can also influence sleep. CONCLUSION: In this paper, we address the issues involved in these phenomena and also discuss the various therapies used to modify them.

Neural Plasticity Is Involved in Physiological Sleep, Depressive Sleep Disturbances, and Antidepressant Treatments.

Depression, which is characterized by a pervasive and persistent low mood and anhedonia, greatly impacts patients, their families, and society. The associated and recurring sleep disturbances further reduce patient's quality of life. However, therapeutic sleep deprivation has been regarded as a rapid and robust antidepressant treatment for several decades, which suggests a complicated role of sleep in development of depression. Changes in neural plasticity are observed during physiological sleep, therapeutic sleep deprivation, and depression. This correlation might help us to understand better the mechanism underlying development of depression and the role of sleep. In this review, we first introduce the structure of sleep and the facilitated neural plasticity caused by physiological sleep. Then, we introduce sleep disturbances and changes in plasticity in patients with depression. Finally, the effects and mechanisms of antidepressants and therapeutic sleep deprivation on neural plasticity are discussed.

Helicid alleviates pain and sleep disturbances in a neuropathic pain-like model in mice.

Natural helicid (4-formylphenyl-O-ß-d-allopyranoside), a main active constituent from seeds of the Chinese herb Helicia nilagirica, has been reported to exert a sedative, analgesic and hypnotic effect, and is used clinically to treat neurasthenic syndrome, vascular headaches and trigeminal neuralgia. In the current study, mechanical allodynia tests, electroencephalograms, electromyogram recordings and c-Fos expression in neuropathic pain-like model mice of partial sciatic nerve ligation were used to investigate the effect of helicid on neuropathic pain and co-morbid insomnia. Our results showed that helicid at a dose of 100, 200 or 400 mg kg-1 could increase the mechanical threshold by 2.5-, 2.8- and 3.1-fold for 3 h after administration, respectively. Helicid at 200 and 400 mg kg-1 given at 07:00 hours increased the amount of non-rapid eye movement sleep in a 3-h period by 1.27- and 1.35-fold in partial sciatic nerve ligated mice. However, helicid (400 mg kg-1 ) given at 21:00 hours did not change the sleep pattern in normal mice. Immunohistochemical study showed that helicid (400 mg kg-1 ) administration could reverse the increase of c-Fos expression in the neurons of the rostral anterior cingulate cortex and tuberomammillary nucleus, and the decrease of c-Fos expression in the ventrolateral preoptic area caused by partial sciatic nerve ligation. These results indicate that helicid is an effective agent for both neuropathic pain and sleep disturbances in partial sciatic nerve ligated mice.

Adenosine A2A receptors in the olfactory bulb suppress rapid eye movement sleep in rodents.

Rapid eye movement (REM) sleep behavior disorder in humans is often accompanied by a reduced ability to smell and detect odors, and olfactory bulbectomized rats exhibit increased REM sleep, suggesting that the olfactory bulb (OB) is involved in REM-sleep regulation. However, the molecular mechanism of REM-sleep regulation by the OB is unknown. Adenosine promotes sleep and its A2A receptors (A2AR) are expressed in the OB. We hypothesized that A2AR in the OB regulate REM sleep. Bilateral microinjections of the A2AR antagonist SCH58261 into the rat OB increased REM sleep, whereas microinjections of the A2AR agonist CGS21680 decreased REM sleep. Similar to the A2AR antagonist, selective A2AR knockdown by adeno-associated virus carrying short-hairpin RNA for A2AR in the rat OB increased REM sleep. Using chemogenetics on the basis of designer receptors exclusively activated by designer drugs, we demonstrated that the inhibition of A2AR neurons increased REM sleep, whereas the activation of these neurons decreased REM sleep. Moreover, using a conditional anterograde axonal tract-tracing approach, we found that OB A2AR neurons innervate the piriform cortex and olfactory tubercle. These novel findings indicate that adenosine suppresses REM sleep via A2AR in the OB of rodents.

The Neurobiological Mechanisms and Treatments of REM Sleep Disturbances in Depression.

Most depressed patients suffer from sleep abnormalities, which are one of the critical symptoms of depression. They are robust risk factors for the initiation and development of depression. Studies about sleep electroencephalograms have shown characteristic changes in depression such as reductions in non-rapid eye movement sleep production, disruptions of sleep continuity and disinhibition of rapid eye movement (REM) sleep. REM sleep alterations include a decrease in REM sleep latency, an increase in REM sleep duration and REM sleep density with respect to depressive episodes. Emotional brain processing dependent on the normal sleep-wake regulation seems to be failed in depression, which also promotes the development of clinical depression. Also, REM sleep alterations have been considered as biomarkers of depression. The disturbances of norepinephrine and serotonin systems may contribute to REM sleep abnormalities in depression. Lastly, this review also discusses the effects of different antidepressants on REM sleep disturbances in depression.

Fasting activated histaminergic neurons and enhanced arousal effect of caffeine in mice.

Caffeine, a popular psychoactive compound, promotes wakefulness via blocking adenosine A2A receptors in the shell of the nucleus accumbens, which projects to the arousal histaminergic tuberomammillary nucleus (TMN). The TMN controls several behaviors such as wakefulness and feeding. Fasting has been reported to activate the TMN histaminergic neurons to increase arousal. Therefore, we propose that caffeine may promote greater arousal under fasting rather than normal feeding conditions. In the current study, locomotor activity recording, electroencephalogram (EEG) and electromyogram recording and c-Fos expression were used in wild type (WT) and histamine H1 receptor (H1R) knockout (KO) mice to investigate the arousal effects of caffeine under fasting conditions. Caffeine (15mg/kg) enhanced locomotor activity in fasted mice for 5h, but only did so for 3h in normally fed animals. Pretreatment with the H1R antagonist pyrilamine abolished caffeine-induced stimulation on locomotor activity in fasted mice. EEG recordings confirmed that caffeine-induced wakefulness for 3h in fed WT mice, and for 5h in fasted ones. A stimulatory effect of caffeine was not observed in fasted H1R KO mice. Furthermore, c-Fos expression was increased in the TMN under fasting conditions. These results indicate that caffeine had greater wakefulness-promoting effects in fasted mice through the mediation of H1R.

Doxepin and diphenhydramine increased non-rapid eye movement sleep through blockade of histamine H1 receptors.

Histaminergic neurons have been reported to play an important role in the regulation of sleep-wake behavior through the histamine H1 receptor (R, H1R). First generation H1R antagonists, such as doxepin and diphenhydramine, produce drowsiness in humans, and are occasionally used to treat insomnia. However, if H1R antagonists function via physically blocking the H1R remains unclear. In the current study, we used H1R knockout (KO) mice to investigate if the sleep-promoting effects of doxepin and diphenhydramine are dependent on blockade of the H1R. When doxepin was administered, non-rapid eye movement (NREM) sleep in wild type (WT) mice increased for 4h, with an increase in the numbers of NREM sleep bouts of 256-512 s and 512-1024 s. These effects were not observed in the H1R KO mice. Furthermore, diphenhydramine increased NREM sleep for 6h in WT, and not in the H1R KO mice after the injection. These results indicate that both doxepin at 15 mg/kg and diphenhydramine at 10 mg/kg induce NREM sleep through blockade of H1R.

Acute administration of fluoxetine normalizes rapid eye movement sleep abnormality, but not depressive behaviors in olfactory bulbectomized rats.

In humans, depression is associated with altered rapid eye movement (REM) sleep. However, the exact nature of the relationship between depressive behaviors and sleep abnormalities is debated. In this study, bilateral olfactory bulbectomy (OBX) was carried out to create a model of depression in rats. The sleep-wake profiles were assayed using a cutting-edge sleep bioassay system, and depressive behaviors were evaluated by open field and forced swimming tests. The monoamine content and monoamine metabolite levels in the brain were determined by a HPLC-electrochemical detection system. OBX rats exhibited a significant increase in REM sleep, especially between 15:00 and 18:00 hours during the light period. Acute treatment with fluoxetine (10 mg/kg, i.p.) immediately abolished the OBX-induced increase in REM sleep, but hyperactivity in the open field test and the time spent immobile in the forced swimming test remained unchanged. Neurochemistry studies revealed that acute administration of fluoxetine increased serotonin (5-HT) levels in the hippocampus, thalamus, and midbrain and decreased levels of the 5-HT metabolite 5-hydroxyindoleacetic acid (5-HIAA). The ratio of 5-HIAA to 5-HT decreased in almost all regions of the brain. These results indicate that acute administration of fluoxetine can reduce the increase in REM sleep but does not change the depressive behaviors in OBX rats, suggesting that there was no causality between REM sleep abnormalities and depressive behaviors in OBX rats.

[Similarity analysis of FTIR of Lapis Micae Aureum].

Similarity analysis of FTIR of Lapis Micae Aureum was carried out to find out the relationship between similarity of infrared spectra and the quality of medicine samples, and try to provide a new method for its quality assessment. FTIR was used to analyze Lapis Micae Aureum samples. Then 6 samples with good quality were picked up to establish a reference infrared spectra by their infrared spectra. Correlation coefficient method and the included angle cosine method were used to calculate the similarity between sample's infrared spectra and the reference infrared spectra. For all those 19 samples with characters in accordance with Ch. P, the similarity is above 0.94, and for the others the similarity is less than 0.94. Although some samples' source meets the requirement of Ch. P, but with poor quality by traditional experience, the similarity is lower than those of good quality. It was concluded that the similarity of infrared spectra of Lapis Micae Aureum is closely related to the quality of medicines. As a result, similarity analysis of FTIR of Lapis Micae Aureum is reliable, and can be used for its quality assessment.