Xingshentongqiao Decoction Mediates Proliferation,Apoptosis, Orexin-A Receptor and Orexin-B Receptor Messenger Ribonucleic Acid Expression and Represses Mitogen-activated Protein Kinase Signaling

Background:Hypocretin (HCRT) signaling plays an important role in the pathogenesis of narcolepsy and can be significantly influenced by Chinese herbal therapy.Our previous study showed that xingshenton...     

唑吡坦对大鼠下丘脑内睡眠相关基因表达的影响

目的 研究催眠药唑吡坦对下丘脑内一些睡眠相关基因表达的影响.方法 大鼠随机分为唑吡坦组和对照组(生理盐水灌胃).采用RT-PCR方法检测下丘脑内GABAA受体α1和α2、褪黑素1a受体、hypocretin及hypocretin受体2的mRNA表达水平.结果 与对照组相比,唑吡坦降低下丘脑内hypocretin及褪黑素1a受体表达(P<0.05),增加hypocretin受体2表达(P<0.05),但对GABAA受体α1和α2表达则无明显影响(P>0.05).结论 唑吡坦在下丘脑可能是通过褪黑素和hypocretin途径发挥其催眠作用,而不是通过GABA途径.     

Microinjection of orexin into the rat nucleus tractus solitarius causes increases in blood pressure

Orexin A (OX-A) and orexin B (OX-B), also known as hypocretin-1 and hypocretin-2, have been suggested to play a role cardiovascular control. The nucleus tractus solitarius (NTS), located in the dorsal medulla plays an essential role in neural control of the cardiovascular system. Orexin-immunoreactive axons have been demonstrated within this nucleus suggesting that NTS may be a site through which OX acts to influence cardiovascular control. We report here that microinjection of OX-A into the NTS of urethane anesthetized rats causes increases in blood pressure (10⁻⁹ M, mean AUC=607.1±65.65 mmHg s, n=5) and heart rate (10⁻⁹ M, mean AUC=16.15±3.3 beats, n=5) which returns to baseline within 90 s. We show that these effects are dose related and site specific. Microinjection of OX-B into NTS elicited similar increases in BP (mean AUC=680.8±128.5 mmHg s, n=4) to that of OX-A suggesting specific actions at the OX₂R receptor. These observations support the conclusion that orexins act as chemical messengers in the NTS likely influencing the excitability of cardiovascular neurons in this region and thus regulating global cardiovascular function.     

Distribution of hypocretin (orexin) immunoreactivity in the feline pons and medulla

The distribution of hypocretin-1 (hcrt-1) and hypocretin-2 (hcrt-2) immunoreactivities in the cat brainstem was examined using immunohistochemical techniques. Hcrt-1- and hcrt-2-positive fibers with varicosities were detected in almost all brainstem regions. However, no hcrt-1- or hcrt-2-immunoreactive neuronal somata were observed in the cat brainstem. Both hcrt-1- and hcrt-2-labeled fibers exhibited different densities in distinct regions of the brainstem. In most brainstem regions, the intensity of hcrt-1 immunoreactivity was higher than that of hcrt-2 immunoreactivity. The highest densities of hcrt-1- and hcrt-2-positive fibers were found in the nucleus raphe dorsalis (RD), the laterodorsal tegmental nucleus (LDT) and the locus coeruleus (LC), suggesting an important role for these peptides in functions related to sleep-wake behavior.     

Pharmacological characterisation of the orexin receptor subtype mediating postsynaptic excitation in the rat dorsal raphe nucleus

Electrophysiological recordings from dorsal raphe nucleus (DRN) neurones in rat brain slices have revealed that the orexins can cause direct and reversible depolarisation of the postsynaptic membrane. Whilst it is known that the membrane depolarisation produced by orexin-A can dramatically increase the firing rate of DRN neurones, quantitative pharmacological analysis that determines the receptor subtype mediating the orexinergic response has not yet been performed. Here, we demonstrate that the rank order of potencies of orexin receptor agonists to excite serotonergic DRN neurones is orexin-A=orexin-B>SB-668875-DM. In contrast, the rank order of potency of these agonists to excite noradrenergic locus coreleus (LC) neurones is orexin-A>orexin-B>SB-668875-DM. We show further that the orexin receptor antagonist, SB-334867-A, inhibits the effects of orexin-A in the LC and DRN with pK_B values of 6.93 and 5.84, respectively, values similar to those calculated for human OX₁ (7.27) and OX₂ (5.60) receptors expressed in CHO cells. These data suggest a differential role for OX₁ and OX₂ receptors in stimulating distinct populations of monoaminergic neurones in the rat CNS with OX₂ receptors exhibiting a more pronounced functional significance in serotonergic neurones and OX₁ in noradrenergic neurones.     

Localization of the orexin system in the gastrointestinal tract of fallow deer

The aim of the present study was to investigate by immunohistochemistry the presence and distribution of the orexin system in the stomach and gut of fallow deer. Abundant orexin A-positive cells were localized in the middle and basal portions of the mucosal glands of the cardial and fundic regions of the stomach. In the same gastric areas, orexin B-positive cells were also found, mainly localized in the basal portion of glands. In the intestinal tract, orexin-containing cells were occasionally found in the duodenal epithelium and in the rectal intestinal glands. Immunoreactivity for orexin receptors, type 1 and 2 (OX1R and OX2R), was not detected in the same stomach regions. OX1R-immunopositivity was observed in the enteric neuron ganglia localized in the submucosal and muscular intestinal layers, while OX2R-immunopositivity was found close in contact with the cytoplasmic membrane of epithelial cells in the small intestine.     

Changes in emotional behavior produced by orexin microinjections in the paraventricular nucleus of the thalamus

The paraventricular nucleus of the midline thalamus (PVT) innervates areas of the extended amygdala known to play a key role in the expression of emotional behaviors. In this study, microinjections of orexins (hypocretins), which have excitatory actions on neurons in the PVT, in the midline thalamus were used to investigate if the PVT modulates the expression of emotional behavior in the open field. First, the approach-avoidance tendency (number and duration of visit to the center area) associated with novelty was examined in orexin treated rats before and after placing a novel object in the center of the open field. Second, the expression of ethological behaviors (rearing, locomotion, freezing, and grooming) in the open field was used to determine the effects of orexins on emotionality. Microinjections of orexin-A (OXA) or orexin-B (OXB) in the PVT decreased exploration of the center area and the novel object indicating that the center area and the object had more aversive properties in orexin treated rats. Both OXA and OXB microinjections in the PVT increased the expression of freezing and grooming behaviors which are indicative of a negative emotional state. The results indicate that microinjections of orexins in the PVT made the test situation more aversive and produced avoidance behaviors. This suggests that orexins may act at the PVT to modulate behaviors associated with a negative emotional state.     

Hypocretin (orexin) loss in Alzheimer's disease

Sleep disturbances in Alzheimer's disease (AD) patients are associated with the severity of dementia and are often the primary reason for institutionalization. These sleep problems partly resemble core symptoms of narcolepsy, a sleep disorder caused by a general loss of the neurotransmitter hypocretin. AD is a neurodegenerative disorder targeting different brain areas and types of neurons. In this study, we assessed whether the neurodegenerative process of AD also affects hypothalamic hypocretin/orexin neurons. The total number of hypocretin-1 immunoreactive neurons was quantified in postmortem hypothalami of AD patients (n = 10) and matched controls (n = 10). In addition, the hypocretin-1 concentration was measured in postmortem ventricular cerebrospinal fluid of 24 AD patients and 25 controls (including the patients and controls in which the hypothalamic cell counts were performed). The number of hypocretin-1 immunoreactive neurons was significantly decreased by 40% in AD patients (median [25th-75th percentiles]); AD 12,935 neurons (9972-19,051); controls 21,002 neurons (16,439-25,765); p = 0.049). Lower cerebrospinal fluid (CSF) hypocretin-1 levels were found in AD patients compared with controls (AD: 275 pg/mL [197-317]; controls: 320 pg/mL [262-363]; p = 0.038). Two AD patients with documented excessive daytime sleepiness showed the lowest CSF hypocretin-1 concentrations (55 pg/mL and 76 pg/mL). We conclude that the hypocretin system is affected in advanced AD. This is reflected in a 40% decreased cell number, and 14% lower CSF hypocretin-1 levels.