Loss of Snord116 impacts lateral hypothalamus, sleep, and food-related behaviors.

Imprinted genes are highly expressed in the hypothalamus; however, whether specific imprinted genes affect hypothalamic neuromodulators and their functions is unknown. It has been suggested that Prader-Willi syndrome (PWS), a neurodevelopmental disorder caused by lack of paternal expression at chromosome 15q11-q13, is characterized by hypothalamic insufficiency. Here, we investigate the role of the paternally expressed Snord116 gene within the context of sleep and metabolic abnormalities of PWS, and we report a significant role of this imprinted gene in the function and organization of the 2 main neuromodulatory systems of the lateral hypothalamus (LH) - namely, the orexin (OX) and melanin concentrating hormone (MCH) - systems. We observed that the dynamics between neuronal discharge in the LH and the sleep-wake states of mice with paternal deletion of Snord116 (PWScrm+/p-) are compromised. This abnormal state-dependent neuronal activity is paralleled by a significant reduction in OX neurons in the LH of mutant mice. Therefore, we propose that an imbalance between OX- and MCH-expressing neurons in the LH of mutant mice reflects a series of deficits manifested in the PWS, such as dysregulation of rapid eye movement (REM) sleep, food intake, and temperature control.

Long-term effects of sleep deprivation on neuronal activity in four hypothalamic areas.

Lack of adequate sleep has become increasingly common in our 24/7 society. Unfortunately diminished sleep has significant health consequences including metabolic and cardiovascular disease and mental disorders including depression. The pathways by which reduced sleep adversely affects physiology and behavior are unknown. We found that 6h of sleep deprivation in adult male rats induces changes in neuronal activity in the lateral hypothalamus, the paraventricular nucleus, the arcuate nucleus and the mammillary bodies. Surprisingly, these alterations last for up to 48h. The data show that sleep loss has prolonged effects on the activity of multiple hypothalamic areas. Our data indicate also that measuring electroencephalographic slow wave activity underestimates the amount of time that the hypothalamus requires to recover from episodes of sleep deprivation. We propose that these hypothalamic changes underlie the well-established relationship between sleep loss and several diseases such as metabolic disorders, stress and depression and that sufficient sleep is vital for autonomic functions controlled by the hypothalamus.

Orexin receptor 2 expression in the posterior hypothalamus rescues sleepiness in narcoleptic mice.

Narcolepsy is caused by a loss of orexin/hypocretin signaling, resulting in chronic sleepiness, fragmented non-rapid eye movement sleep, and cataplexy. To identify the neuronal circuits underlying narcolepsy, we produced a mouse model in which a loxP-flanked gene cassette disrupts production of the orexin receptor type 2 (OX2R; also known as HCRTR2), but normal OX2R expression can be restored by Cre recombinase. Mice lacking OX2R signaling had poor maintenance of wakefulness indicative of sleepiness and fragmented sleep and lacked any electrophysiological response to orexin-A in the wake-promoting neurons of the tuberomammillary nucleus. These defects were completely recovered by crossing them with mice that express Cre in the female germline, thus globally deleting the transcription-disrupter cassette. Then, by using an adeno-associated viral vector coding for Cre recombinase, we found that focal restoration of OX2R in neurons of the tuberomammillary nucleus and adjacent parts of the posterior hypothalamus completely rescued the sleepiness of these mice, but their fragmented sleep was unimproved. These observations demonstrate that the tuberomammillary region plays an essential role in the wake-promoting effects of orexins, but orexins must stabilize sleep through other targets.

Electrical stimulation in the lateral hypothalamus in rats in the activity-based anorexia model.

OBJECT: One quarter of patients with anorexia nervosa have a poor outcome and continue to suffer chronically or die. Electrical brain stimulation may be of therapeutic benefit in some of these patients; however, the brain target for inducing symptom relief is unknown. In this study, the authors evaluated the effects of acute and chronic electrical stimulation in the lateral hypothalamus on food intake, locomotor activity, and survival time in rats in an activity-based anorexia model. METHODS: In an acute experiment, the authors electrically stimulated at 100 Hz and 0, 25, 50 and 75% of the maximal stimulation amplitude (that is, the amplitude leading to severe side effects) in the lateral hypothalamus on consecutive days during 4 test sessions in 10 rats and evaluated food intake and locomotor activity. In a chronic experiment, they compared food intake, wheel revolutions, and survival time between 6 rats that underwent electrical stimulation in the lateral hypothalamus (50% of maximal stimulation amplitude) and 8 rats that did not undergo stimulation. RESULTS: In the acute experiment, overall electrical stimulation (25, 50, and 75% combined) and stimulation at 75% of the maximal stimulation amplitude significantly decreased the locomotor activity. However, if the authors omitted results of 1 rat, in which the electrode tip was not located in the lateral hypothalamus on one side but rather in the supraoptic chiasm, the remaining results did not yield significance. No other differences were observed. CONCLUSIONS: When the findings of the current study are extrapolated to patients with anorexia nervosa, the authors do not expect major effects on symptoms with electrical stimulation at high frequency in the lateral hypothalamus.

[Effects of Baobaole oral liquid on neuron excitability of feeding center in anorectic rats].

OBJECTIVE: To investigate the effects of Baobaole oral liquid on neuronal excitability in lateral hypothalamic area (LHA) and ventromedial hypothalamic nuclear (VMN) in anorectic rats. METHODS: The anorectic rat model was established by feeding with special prepared forage for a week, and then Baobaole oral liquid, a liquid extract of a compound traditional Chinese medicine for activating spleen, was administered once a day for 3 weeks. Finally, extracellular recording from LHA and VMN neurons in rats were made in order to characterize their responses to gastric vagal nerve stimulation and intravenous injection of glucose in the normal, untreated, and Baobaole-treated groups. RESULTS: There was no statistical difference in response characteristics of LHA neurons to gastric vagal stimulation among 3 groups. The duration of VMN neuron excitation response to gastric vagal nerve stimulation in the untreated group was significantly longer than that of the normal control group (P<0.01), while the required stimulation intensity was significantly decreased (P<0.01). Moreover, among the neurons responding to the gastric vagal stimulation in the untreated group, the number of glycemia-sensitive neurons decreased in LHA and increased in VMN (P<0.01). The gastric vagal stimulation induced neuron responses in LHA and VMN of the Baobaole-treated group were not significantly changed as compared with the normal control group (P<0.01), and neither were the intravenous injection of glucose induced responses. CONCLUSION: Baobaole oral liquid can modulate the sensitivity of LHA and VMN neurons to the peripheral signal and make the coordination between LHA and VMN neurons in order to improve the appetite of anorectic rats.

[Effect of er'bao granule on integration of ingestion behavior-related information by neurons in lateral hypothalamic area of anorexia rats].

OBJECTIVE: To confirm the effect of Er'bao granule (EBG) on the sensitivity to peripheral afferent signal of neurons in lateral hypothalamic area (LHA) to illustrate the central mechanism of EBG in promoting ingestion behavior. METHODS: The anorexia rat model was established by feeding special prepared forage for one week, and all the model rats were administrated with EBG by gavage for 3 weeks. The spontaneous discharge of LHA neurons was recorded using electro-physiological extracellular recording method, and its response to electrical stimulus on gastric vagus nerve and intravenous injection of glucose were observed and compared among the normal, model and treated groups. RESULTS: As compared with the normal group, among the LHA neurons responding to afferent gastric vagal impulse, the proportion of glycemia-sensitive neurons in the model group was significantly decreased (P <0.01), but insignificant difference was shown in comparison between the treated group and the normal group. CONCLUSION: EBG play a role in regulating the sensitivity of LHA neurons to peripheral afferent signal and thus to influence the multi-afferent information integration of ingestion central neurons.

Narp immunostaining of human hypocretin (orexin) neurons: loss in narcolepsy.

OBJECTIVE: To investigate whether neuronal activity-regulated pentraxin (Narp) colocalizes with hypocretin (Hcrt or orexin) in the normal human brain and to determine if Narp staining is lost in the narcoleptic human brain. BACKGROUND: Human narcolepsy is characterized by a loss of the peptide hypocretin in the hypothalamus. This loss could result from the degeneration of neurons containing hypocretin or from a more specific loss of the ability of these neurons to synthesize Hcrt. Narp has been found to colocalize with hypocretin in the rat hypothalamus. METHODS: We investigated the distribution of Narp in three normal and four narcoleptic human postmortem brains using immunohistochemistry with an antibody to Narp. Colocalization studies of Narp and hypocretin were also performed in two normal brains using immunohistochemistry with an antibody to Narp and an antibody to hypocretin. RESULTS: We found that Narp colocalizes with hypocretin in the lateral hypothalamic area (LHA), the dorsomedial hypothalamus (DMH), the dorsal hypothalamic area (DHA), and the posterior hypothalamic area (PHA) of the normal human. The number of Narp-positive neurons was reduced by 89% in these areas of the narcoleptic hypothalamus. In contrast, Narp staining in the paraventricular (Pa) and supraoptic nuclei (SO) of the human hypothalamus did not differ between normal and narcoleptic brains. CONCLUSIONS: This finding supports the hypothesis that narcolepsy results from the specific loss of hypocretin neurons. Loss of hypothalamic Narp may contribute to the symptoms of narcolepsy.

Hypocretin-1 (orexin A) deficiency in acute traumatic brain injury.

Hypocretin-1 is involved in the regulation of the sleep-wake cycle. The authors prospectively assessed CSF hypocretin-1 levels in 44 consecutive patients with acute traumatic brain injury (TBI). Compared with controls, hypocretin-1 levels were abnormally lower in 95% of patients with moderate to severe TBI and in 97% of patients with posttraumatic brain CT changes. Hypocretin-1 deficiency after TBI may reflect hypothalamic damage and be linked with the frequent development of posttraumatic sleep-wake disorders.

Distinct narcolepsy syndromes in Orexin receptor-2 and Orexin null mice: molecular genetic dissection of Non-REM and REM sleep regulatory processes.

Narcolepsy-cataplexy, a neurological disorder associated with the absence of hypothalamic orexin (hypocretin) neuropeptides, consists of two underlying problems: inability to maintain wakefulness and intrusion of rapid eye movement (REM) sleep into wakefulness. Here we document, using behavioral, electrophysiological, and pharmacological criteria, two distinct classes of behavioral arrests exhibited by mice deficient in orexin-mediated signaling. Both OX2R(-/-) and orexin(-/-) mice are similarly affected with behaviorally abnormal attacks of non-REM sleep ("sleep attacks") and show similar degrees of disrupted wakefulness. In contrast, OX2R(-/-) mice are only mildly affected with cataplexy-like attacks of REM sleep, whereas orexin(-/-) mice are severely affected. Absence of OX2Rs eliminates orexin-evoked excitation of histaminergic neurons in the hypothalamus, which gate non-REM sleep onset. While normal regulation of wake/non-REM sleep transitions depends critically upon OX2R activation, the profound dysregulation of REM sleep control unique to the narcolepsy-cataplexy syndrome emerges from loss of signaling through both OX2R-dependent and OX2R-independent pathways.

[Morpho-functional status of large-cell hypothalamic nuclei following chronic exposure to wide-range electromagnetic impulses]. / Morfofunktsional'noe sostoianie krupnokletochnykh iader gipotalamusa pri khronicheskom vozdeistvii shirokopolosnykh élektromagnitnykh impul'sov.

In a experiment with white nubilous male rats the morphofuntional state of secretory neurons (SN) of the large-cell hypothalamic nuclei (LCHN) was evaluated with the morphological, morphometric and statistical methods following electromagnetic exposure (500, 100 and 50 impulses once a week) inducing in the animal body the averaged current densities of 1.5 kA/m2. It was stated that 100 EMI a week called forth opposite LCHN reactions, that is suppression of synthesis and elimination of SN neuro-secret in supraoptic nuclei and their activation in the paraventricular nuclei. LCHN reaction to the other frequencies of EM impulses was uniform and included rearrangement of both neurosecretory centers for a lower functional activity. Decrease in the number of effectively functioning SN due to the EM exposure may point to a dead-aptive effect of this factor.

Effects of auricular stimulation on feeding-related hypothalamic neuronal activity in normal and obese rats.

It is known that auriculotherapy occasionally affects dramatic body weight reduction for obese patients, although the physiological and anorexigenic functions are not clear. Effects of auricular stimulation on feeding-related lateral (LHA) and ventromedial (VMH) hypothalamic neuronal activity in normal and experimental (hypothalamic and dietary) obese rats were investigated. The LHA and/or VMH neuronal activity were recorded from feeding-related regions in Wistar SPF/VAF male and experimental (hypothalamic and dietary) obese rats, anesthetized with urethane-chloralose, under stereotaxic coordination. Recording was through 3 M KCI glass microelectrodes, while stimulating the ipsilateral vagal innervated region of the auricle. This is equivalent to the cavum conchae in the human, and was identified by resistance less than 10-50 k omega. The stimulating electrode was a stainless steel ear acupuncture (0.12 x 2.0 mm). The latency of potentials evoked in the LHA by unilateral stimulation of a specific site in the ear was 28.1 +/- 3.3 ms (8-92, n = 41). LHA neuronal activity was depressed 45.6% (n = 12, p < 0.01), and VMH activity was excited (60.5%, n = 18, p < 0.01). The auricular acupuncture stimulation clearly modulates feeding-related hypothalamic neuronal activity of experimental (both hypothalamic and dietary) obese rats. These auricle acupuncture stimulation effects were correlated to the degree of obesity. In conclusion, the results suggest that auricular acupuncture stimulation may not reduce appetite, but is more likely concerned with satiation formation and preservation. Thus, auricular acupuncture should be more effective on obese rats than on normal rats.

GABA inhibition of lateral hypothalamic neurons: role of reticular thalamic afferents.

GABA and reticular thalamic (RT) stimulation induced inhibition of lateral hypothalamic (LH) neuronal activity was studied to determine if RT inhibitory input to the LH is mediated by stimulation of GABA receptors. Seven barrel electrodes were utilized to record simultaneously from the LH during microiontophoretic application of GABA, glycine, bicuculline, picrotoxin, and electrical stimulation of the RT. GABA produced an ejection current-related decrease in LH neuronal activity that was antagonized, in a dose-related manner, by the simultaneous administration of picrotoxin or bicuculline. LH neurons were much less sensitive to glycine inhibition which also was relatively insensitive to the GABA receptor antagonists. RT electrical stimulation provided a short latency inhibitory input to LH neurons that was mimicked by the microiontophoretic administration of GABA. In addition, the microiontophoretic application of picrotoxin or bicuculline blocked the RT stimulation induced inhibition of LH neuronal activity. These data indicate that the inhibitory effects of both GABA and RT synaptic inputs onto LH neurons are mediated by stimulation of GABAA receptors and substantiates the involvement of GABA as the inhibitory transmitter of thalamic to hypothalamic projections.

GABA-related feeding control in genetically obese rats.

Feeding in response to glucoprivation induced by 2-deoxy-D-glucose (2-DG) is impaired in genetically obese (Zucker) rats. Muscimol, a GABAA-agonist (0.5 nmol/0.5 microliter in each area) increased food intake in lean rats over 3 h but in fatty rats only at 30 min after infusion into the VMH. Injection of muscimol into the DMH and PVN increased feeding of both phenotypes. Picrotoxin, a non-competitive GABAA-antagonist (0.1 nmol/0.5 microliter) increased food intake after infusion into the LH of both phenotypes and decreased food intake over a 3 h period when infused into the VMH. DMH and PVN of fatty rats. In the lean littermates, picrotoxin was only effective in reducing food intake at 30 min after infusion into the VMH and PVN but not the DMH. The present results suggest that the fatty Zucker rat has a disturbance in the GABA-related regulatory mechanism of feeding behavior in the ventromedial hypothalamus, which may be responsible for the impaired response to glucoprivation found in these rats.

[Effect of electro-acupuncture of zusanli on unit discharges in the lateral hypothalamic area induced by stomach distension].

Previous studies in our laboratory have shown that some unit discharges of the neurons in Feeding Centre of the lateral hypothalamic area (LHA) may be inhibited by distending stomach. The present study was performed to observe the effect of electro-acupuncture of "Zusanli" point on the discharge-inhibitory reaction induced by distending stomach in rats. Among 52 unit discharges observed, 36 (69.2%) showed that electro-acupuncturing "Zusanli" point abolished the inhibitory reaction induced by distending stomach. The durations of the effect range from 5 to 15 minutes. These results indicate that the somatic input from "Zusanli" plant may influence the reactivity of Feeding Centre of LHA to the activity of stomach.

Vegetative dysfunctions of the hypothalamus.

Experiment and clinical evidence of hypothalamic influence on autonomic function has accumulated since the early part of this century. Localization of hypothalamic lesions is difficult, and damage must be bilateral to produce symptoms. Caloric balance may be altered, with ventromedial lesions causing hyperphagia, and lateral hypothalamic lesions producing a syndrome of aphagia and weight loss in experimental animals. Gastric ulcerations are associated with brainstem lesions, including the diencephalon. Anterior hypothalamic lesions cause hyperthermia, while posterior lesions result in hypothermia, often accompanied by disturbance of sweating mechanisms. Disorders of sleep and wakefulness are seen clinically in encephalitis lethargica and Wernicke's syndrome, both associated with hypothalamic damage. The hypothalamus is the regulator and co-ordinator of central autonomic activity.

[Participation of neurons of different hypothalamic areas in the reaction of the body to hypoxia]. / Uchastie neironov razlichnykh otdelov gipotalamusa v reaktsii organizma na gipoksiiu.

In anesthetized cats, spontaneous activity was recorded in neurons of the anterior, supraoptic, lateral, ventro-medial and posterior nuclei of the hypothalamus under conditions of oxygen deficit induced by the blood loss or discontinuation of artificial respiration. Phases of activation and suppression of electric activity of different hypothalamic nuclei did not develop simultaneously. At the onset of hypoxia development of activation involved the anterior areas and then propagated to the posterior hypothalamic structures. The supraoptic nucleus seems to play a triggering role in the development of compensatory-adaptive response in the hypothalamus under the effect of stress.

[Impulse activity of hypothalamic neurons during asphyxia]. / Impul'snaia aktivnost' gipotalamicheskikh neironov v usloviiakh asfiksii.

In immobilized cats, asphyxia produced biphasic changes of the impulse activity of hypothalamic neurons lasting 3--5 min: a short latency period was followed by an increase of firing rate and then gradual and complete disappearance of the discharges. The inhibition of the impulse activity was similar to that during cathodic depression. On the average, the impulse activity in asphyxia lasted during 171 +/- 14 sec in the posterior nucleus, 138 +/- 10 sec in the lateral nucleus, 144 +/- 10 sec in the ventromedial nucleus and 135 +/- 10 sec in the supraoptic nucleus of the hypothalamus. After renewal of artificial respiration the spike discharges reappeared.