Evidence suggests that hypocretins (Hcrt), also called orexins, promote behavioral arousal and suppress rapid eye movement (REM) sleep. Loss or dysfunction of Hcrt system is associated with symptoms of narcolepsy including excessive sleepiness. In the brain, Hcrt neurons are localized within the perifornical-lateral hypothalamic area (PF-LHA). A majority of PF-LHA neurons are active during behavioral arousal and exhibit lower activities during quiet waking (QW) and non-REM sleep. In contrast, a majority of neurons in the ventrolateral preoptic area (VLPO) and the median preoptic nucleus (MnPN) of the preoptic region are active during sleep. Most of the sleep-active neurons in MnPN are GABAergic. MnPN GABAergic neurons constitute a source of afferents to PF-LHA. The identity of neurotransmitters/neuromodulators that regulate the state-dependent activity PF-LHA arousal systems is unknown. The role of Hcrts in regulating the state-dependent activity of sleep-active neurons in MnPN and VLPO is uncharacterized. First, we hypothesize that increased adenosinergic inhibition contributes to the suppression of PF-LHA neuronal activity during QW, and their further suppression during non-REM sleep results from increased gamma-amino butyric acid (GABA)-mediated inhibition. We will quantify the effects of adenosine and GABA agonists and antagonists delivered through an adjacent microdialysis probe on the state-dependent extracellular activity of PF-LHA neurons in freely behaving rats. Second, we hypothesize that the MnPN promotes sleep in part by inhibiting the wake-promoting systems in PF-LHA and that this inhibition is mediated via a GABAergic mechanism. We will examine effects of the MnPN electrical and chemical stimulation on the state-dependent activity of PF-LHA neurons in the presence and the absence of GABA receptor antagonist. The effects of GABAergic and adenosinergic drugs as well as effects of MnPN stimulation on Hcrt neurons will be further studied by double label immunostaining for hcrt-1 peptide and for c-Fos protein. We found that hcrt-1 microinjection into preoptic area promotes arousal. Third, we hypothesize that Hcrt system promotes arousal in part by inhibiting sleep-active neurons in MnPN and VLPO. We will determine the ability of focal microdialysis perfusion of Hcrts to suppress the activity of sleep-active neurons in VLPO and MnPN. Proposed studies will significantly advance our understanding of the neurotransmitter basis of the state-related control of PF-LHA arousal systems including Hcrt neurons and their interactions with preoptic sleep-promoting systems. This will contribute to the search for more targeted and specific therapeutic strategies for sleep disorders.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Research Project (R01)
Project #
5R01NS050939-06
Application #
6924548
Study Section
Biological Rhythms and Sleep Study Section (BRS)
Program Officer
Mitler, Merrill
Project Start
2000-05-15
Project End
2009-06-30
Budget Start
2005-07-01
Budget End
2006-06-30
Support Year
6
Fiscal Year
2005
Total Cost
$240,685
Indirect Cost
Name
Sepulveda Research Corporation
Department
Type
DUNS #
030380682
City
Sepulveda
State
CA
Country
United States
Zip Code
91343
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Rai, S; Kumar, S; Alam, M A et al. (2010) A1 receptor mediated adenosinergic regulation of perifornical-lateral hypothalamic area neurons in freely behaving rats. Neuroscience 167:40-8
Alam, M N; Kumar, S; Suntsova, N et al. (2010) GABAergic regulation of the perifornical-lateral hypothalamic neurons during non-rapid eye movement sleep in rats. Neuroscience 167:920-8
Alam, Md Noor; Kumar, Sunil; Rai, Seema et al. (2009) Role of adenosine A(1) receptor in the perifornical-lateral hypothalamic area in sleep-wake regulation in rats. Brain Res 1304:96-104
Suntsova, N; Kumar, S; Guzman-Marin, R et al. (2009) A role for the preoptic sleep-promoting system in absence epilepsy. Neurobiol Dis 36:126-41
Kumar, Sunil; Szymusiak, Ronald; Bashir, Tariq et al. (2008) Inactivation of median preoptic nucleus causes c-Fos expression in hypocretin- and serotonin-containing neurons in anesthetized rat. Brain Res 1234:66-77
Kumar, Sunil; Szymusiak, Ronald; Bashir, Tariq et al. (2007) Effects of serotonin on perifornical-lateral hypothalamic area neurons in rat. Eur J Neurosci 25:201-12
Suntsova, Natalia; Guzman-Marin, Ruben; Kumar, Sunil et al. (2007) The median preoptic nucleus reciprocally modulates activity of arousal-related and sleep-related neurons in the perifornical lateral hypothalamus. J Neurosci 27:1616-30
Alam, Md Noor; Kumar, Sunil; Bashir, Tariq et al. (2005) GABA-mediated control of hypocretin- but not melanin-concentrating hormone-immunoreactive neurones during sleep in rats. J Physiol 563:569-82