Arousal systems

GABA release and GABAergic control of arousal systems... 

Some arousal-related neurotransmitters, including noradrenaline, serotonin, and acetylcholine, feed back to inhibit POA sleep-active neurons. This aspect of the system has been reviewed previously (McGinty Szymusiak, 2000 Saper et al., 2001). Therefore, once sleep-active neurons are activated, arousal-related neurons are inhibited, and inhibitory control of sleep-active neurons by arousal systems is reduced. In this way, sleep onset is facilitated. That is, the mutually inhibitory systems can switch more quickly from wake to sleep, and back. These mutually inhibitory interactions also promote stability of both waking and sleep. 

Sleep-related VLPO neurons exhibit increased discharge within NREM during recovery sleep after deprivation, and their discharge rates were correlated with the amount of SWA within sleep episodes (Szymusiak et al., 1998). Thus, VLPO-type sleep-active neurons may directly control the SW content of the NREM EEG, presumably by suppressing arousal systems. 

Brown, R. E., Sergeeva, O. A., Eriksson, K. S. Haas, H. L. (2002). Convergent excitation of dorsal raphe serotonin neurons by multiple arousal systems (orexin/hypocretin, histamine and noradrenaline). J. Neurosci. 22, 8850-9. 

Jones, B. E. (2003). Arousal systems. Front Biosci. 8, S438-51. 

Abrahamson, E. E., Leak, R. K. Moore, R. Y. (2001). The suprachiasmatic nucleus projects to posterior hypothalamic arousal systems. Neuroreport 12, 435-40. 

Li, Y Gao, X. B., Sakurai, T. van den Pol, A. N. (2002). Hypocretin/orexin excites hypocretin neurons via a local glutamate neuron-A potential mechanism for orchestrating the hypothalamic arousal system. Neuron 36, 1169-81. 

Immunohistochemical and electrophysiological studies of the hypothalamic preoptic area (POA), which plays a major role in sleep promotion, have identified a subset of sleep-active ventrolateral POA (VLPO) neurons (Sherin et al. 1996 Szymusiak et al. 1998). A tightly clustered group of VLPO neurons appears to promote non-REM sleep, by suppression of the histaminergic arousal system, which... 

Fu L. Y., Acuna-Goycolea C., van den Pol A. N. (2004). Neuropeptide Y inhibits hypocretin/orexin neurons by multiple presynaptic and postsynaptic mechanisms tonic depression of the hypothalamic arousal system. J. Neurosci. 

MODULATION OF CORTICAL CIRCUITS BY THE ASCENDING "AROUSAL" SYSTEMS... 

It is hard to believe that one could have a severed biceps muscle and not notice it, but when fighters are pumped up they can take inordinate punishment without pain. The arousal system that normally keeps us awake keeps us ultra-awake when we are after someone or when someone is after us. This hyperarousal can be associated with elation if we are the predator or with fear if we are the prey. In the heat of battle either of these emotions can be exchanged for the other, or mixed, or be accompanied by rage, depending on the strategy we adopt. 

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