introduction: it has been shown that orexin peptides have a role in opioid withdrawal behaviors. orexin-expressing neurons that are present in the hypothalamic nuclei send dense projections to the locus coeruleus (lc). withdrawal syndrome is temporally associated with hyperactivity of lc neurons. however, lc neurons do not show withdrawalinduced hyperactivity in the brain slices from morphine-d...

The circadian clock housed in the suprachiasmatic nucleus (SCN) controls various circadian rhythms including daily sleep–wake cycles. Using dual tract-tracing, we recently showed that the medial preoptic area (MPA), subparaventricular zone (SPVZ) and dorsomedial hypothalamic nucleus (DMH) are well positioned to relay SCN output to two key sleep-promoting nuclei, namely, the ventrolateral and me...

Orexin A and B are involved in feeding behaviors, and recently fibers containing these peptides were found in the rat olfactory bulb. These fibers, which originate from the lateral and posterior hypothalamus and the perifornical area, are distributed in the glomerular, mitral cell, and granule cell layers. Orexin receptors are mainly expressed by mitral cells. In the present study, RT-PCR exper...

In this study, we investigated the role of orexinergic systems in dopamine-related behaviors induced by the mu-opioid receptor agonist morphine in rodents. Extensive coexpression of tyrosine hydroxylase with orexin receptors was observed in the mouse ventral tegmental area (VTA). The levels of dopamine and its major metabolites in the nucleus accumbens were markedly increased by the microinject...

Orexins (synonymous with hypocretins) are recently discovered neuropeptides made exclusively in hypothalamus. Behavioral, anatomical, and neurophysiological studies show that a subset of these cells, specifically those in lateral hypothalamus (LH), are involved in reward processing and addictive behaviors. Fos expression in LH orexin neurons varied in proportion to conditioned place preference ...

Initial research on the functional significance of two novel hypothalamic neuropeptides, orexin-A and orexin-B, suggested an important role in appetite regulation. Since then, however, these peptides have also been shown to influence a wide range of other physiological and behavioural processes. In this paper, we review the now quite extensive literature on orexins and appetite control, and con...

THE LAST DECADES HAVE WITNESSED an upsurge of neuropeptide research. These substances regulate or influence various functions like appetite, water intake, learning and memory, adaptive responses to environmental stress, thermoregulation and fever, social behavior, and sleep. One function may be affected by several peptides, and a single peptide can be involved in different functions—a general a...