Orexins (also named hypocretins) are recently discovered neuropeptides made exclusively in the hypothalamus. Recent studies have shown that orexin cells located specifically in lateral hypothalamus (LH) are involved in motivated behavior for drugs of abuse as well as natural rewards. Administration of orexin has been shown to stimulate food consumption, and orexin signaling in VTA has been impl...

Orexin (hypocretin) appears to play a role in the regulation of energy balances. Previous reports have indicated that orexin-containing neurons are found only in the lateral hypothalamic (LH) area. We show that a subset of neurons in the gut which also express leptin receptors display orexin-like immunoreactivity and express functional orexin receptors. Orexin excites secretomotor neurons in th...

The absence of orexin results in narcolepsy-cataplexy. While the function of the central orexinergic system in sleep regulation has been well studied, the role of orexin in motor control is largely unknown. Here, we show that orexin-A acts via OX(1) and OX(2) receptors to directly depolarize neurons in the rat lateral vestibular nucleus (LVN), a subcortical motor center, and enhance their sensi...

We addressed the role of nitric oxide (NO) in orexin neuron degeneration that has been observed under various pathological conditions. Administration of an NO donor NOC18 (50 nmol) into the third ventricle of mice resulted in a significant decrease of orexin-immunoreactive (-IR) neurons, in contrast to a modest change in melanin-concentrating hormone-IR neurons. In addition, NOC18 promoted form...

Orexin deficiency results in the sleep disorder narcolepsy in many mammalian species, including mice, dogs, and humans, suggesting that the orexin system is particularly important for normal regulation of sleep/wakefulness states, and especially for maintenance of wakefulness. This review discusses animal models of narcolepsy; the contribution of each orexin receptor subtype to the narcoleptic ...

In this study, we have compared the abilities of orexin-A and orexin-B and variants of orexin-A to activate different Ca(2+) responses (influx and release) in human OX(1) and OX(2) receptor- expressing Chinese hamster ovary cells. Responses mediated by activation of both receptor subtypes with either orexin-A or -B were primarily dependent on extracellular Ca(2+), suggesting similar activation ...

Hypothalamic orexin neurons project to the hindbrain, and 4th-ventricle intracerebroventricular (4th-icv) injection of orexin-A treatment increases food intake. We assessed the effects of hindbrain orexin-A and the orexin-1-receptor antagonist SB334867 on meal pattern in rats consuming standard chow. When injected 4th-icv shortly before dark onset, lower doses of orexin-A increased food intake ...

Both orexin and serotonin (5-HT) have important roles in the regulation of sleep-wakefulness, as well as in feeding behavior. We examined the effects of 5-HT on orexin/hypocretin neurons, using hypothalamic slices prepared from orexin/enhanced green fluorescent protein (EGFP) transgenic mice in which EGFP is expressed exclusively in orexin neurons. Patch-clamp recording from EGFP-expressing cel...

Introduction: It is known that acute and chronic stress induce hormonal and neuronal changes which affecting both pain threshold and nociceptive behaviours. Orexin plays an important role in modulation of pain and stress. Considering pain modulation during stress and the role of orexin in pain and stress, orexin might be involved in pain modulation during stress.We evaluated the involvement ...